mirror/postgresql
2
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2024-12-15 08:20:16 +08:00
Code Issues Packages Projects Releases Wiki Activity
59c2617af3
postgresql/contrib/postgres_fdw/postgres_fdw.c
Tom Lane 5ee190f8ec Rationalize use of list_concat + list_copy combinations. 
In the wake of commit 1cff1b95a, the result of list_concat no longer
shares the ListCells of the second input.  Therefore, we can replace
"list_concat(x, list_copy(y))" with just "list_concat(x, y)".

To improve call sites that were list_copy'ing the first argument,
or both arguments, invent "list_concat_copy()" which produces a new
list sharing no ListCells with either input.  (This is a bit faster
than "list_concat(list_copy(x), y)" because it makes the result list
the right size to start with.)

In call sites that were not list_copy'ing the second argument, the new
semantics mean that we are usually leaking the second List's storage,
since typically there is no remaining pointer to it.  We considered
inventing another list_copy variant that would list_free the second
input, but concluded that for most call sites it isn't worth worrying
about, given the relative compactness of the new List representation.
(Note that in cases where such leakage would happen, the old code
already leaked the second List's header; so we're only discussing
the size of the leak not whether there is one.  I did adjust two or
three places that had been troubling to free that header so that
they manually free the whole second List.)

Patch by me; thanks to David Rowley for review.

Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-08-12 11:20:18 -04:00

6569 lines
197 KiB
C
Raw Blame History

/*-------------------------------------------------------------------------
*
* postgres_fdw.c
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_class.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/float.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/sampling.h"
#include "utils/selfuncs.h"
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/* If no remote estimates, assume a sort costs 20% extra */
#define DEFAULT_FDW_SORT_MULTIPLIER 1.2
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item
* can be fetched with list_nth(). For example, to get the SELECT statement:
* sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
*/
enum FdwScanPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of attribute numbers retrieved by the SELECT */
FdwScanPrivateRetrievedAttrs,
/* Integer representing the desired fetch_size */
FdwScanPrivateFetchSize,
/*
* String describing join i.e. names of relations being joined and types
* of join, added when the scan is join
*/
FdwScanPrivateRelations
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ModifyTable node referencing a postgres_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server
* 2) Integer list of target attribute numbers for INSERT/UPDATE
* (NIL for a DELETE)
* 3) Boolean flag showing if the remote query has a RETURNING clause
* 4) Integer list of attribute numbers retrieved by RETURNING, if any
*/
enum FdwModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as an integer Value node) */
FdwModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwModifyPrivateRetrievedAttrs
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ForeignScan node that modifies a foreign table directly. We store:
*
* 1) UPDATE/DELETE statement text to be sent to the remote server
* 2) Boolean flag showing if the remote query has a RETURNING clause
* 3) Integer list of attribute numbers retrieved by RETURNING, if any
* 4) Boolean flag showing if we set the command es_processed
*/
enum FdwDirectModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwDirectModifyPrivateUpdateSql,
/* has-returning flag (as an integer Value node) */
FdwDirectModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwDirectModifyPrivateRetrievedAttrs,
/* set-processed flag (as an integer Value node) */
FdwDirectModifyPrivateSetProcessed
};
/*
* Execution state of a foreign scan using postgres_fdw.
*/
typedef struct PgFdwScanState
{
Relation rel; /* relcache entry for the foreign table. NULL
* for a foreign join scan. */
TupleDesc tupdesc; /* tuple descriptor of scan */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of SELECT command */
List *retrieved_attrs; /* list of retrieved attribute numbers */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/* batch-level state, for optimizing rewinds and avoiding useless fetch */
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
int fetch_size; /* number of tuples per fetch */
} PgFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct PgFdwModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
char *p_name; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
/* info about parameters for prepared statement */
AttrNumber ctidAttno; /* attnum of input resjunk ctid column */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
/* for update row movement if subplan result rel */
struct PgFdwModifyState *aux_fmstate; /* foreign-insert state, if
* created */
} PgFdwModifyState;
/*
* Execution state of a foreign scan that modifies a foreign table directly.
*/
typedef struct PgFdwDirectModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of UPDATE/DELETE command */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
bool set_processed; /* do we set the command es_processed? */
/* for remote query execution */
PGconn *conn; /* connection for the update */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
PGresult *result; /* result for query */
int num_tuples; /* # of result tuples */
int next_tuple; /* index of next one to return */
Relation resultRel; /* relcache entry for the target relation */
AttrNumber *attnoMap; /* array of attnums of input user columns */
AttrNumber ctidAttno; /* attnum of input ctid column */
AttrNumber oidAttno; /* attnum of input oid column */
bool hasSystemCols; /* are there system columns of resultRel? */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwDirectModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct PgFdwAnalyzeState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *retrieved_attrs; /* attr numbers retrieved by query */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
ReservoirStateData rstate; /* state for reservoir sampling */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwAnalyzeState;
/*
* This enum describes what's kept in the fdw_private list for a ForeignPath.
* We store:
*
* 1) Boolean flag showing if the remote query has the final sort
* 2) Boolean flag showing if the remote query has the LIMIT clause
*/
enum FdwPathPrivateIndex
{
/* has-final-sort flag (as an integer Value node) */
FdwPathPrivateHasFinalSort,
/* has-limit flag (as an integer Value node) */
FdwPathPrivateHasLimit
};
/* Struct for extra information passed to estimate_path_cost_size() */
typedef struct
{
PathTarget *target;
bool has_final_sort;
bool has_limit;
double limit_tuples;
int64 count_est;
int64 offset_est;
} PgFdwPathExtraData;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation
{
Relation rel; /* foreign table's relcache entry. */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
/*
* In case of foreign join push down, fdw_scan_tlist is used to identify
* the Var node corresponding to the error location and
* fsstate->ss.ps.state gives access to the RTEs of corresponding relation
* to get the relation name and attribute name.
*/
ForeignScanState *fsstate;
} ConversionLocation;
/* Callback argument for ec_member_matches_foreign */
typedef struct
{
Expr *current; /* current expr, or NULL if not yet found */
List *already_used; /* expressions already dealt with */
} ec_member_foreign_arg;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(postgres_fdw_handler);
/*
* FDW callback routines
*/
static void postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *foreignrel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan);
static void postgresBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node);
static void postgresReScanForeignScan(ForeignScanState *node);
static void postgresEndForeignScan(ForeignScanState *node);
static void postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation);
static List *postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags);
static TupleTableSlot *postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo);
static void postgresBeginForeignInsert(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo);
static void postgresEndForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo);
static int postgresIsForeignRelUpdatable(Relation rel);
static bool postgresPlanDirectModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginDirectModify(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateDirectModify(ForeignScanState *node);
static void postgresEndDirectModify(ForeignScanState *node);
static void postgresExplainForeignScan(ForeignScanState *node,
ExplainState *es);
static void postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es);
static void postgresExplainDirectModify(ForeignScanState *node,
ExplainState *es);
static bool postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
static List *postgresImportForeignSchema(ImportForeignSchemaStmt *stmt,
Oid serverOid);
static void postgresGetForeignJoinPaths(PlannerInfo *root,
RelOptInfo *joinrel,
RelOptInfo *outerrel,
RelOptInfo *innerrel,
JoinType jointype,
JoinPathExtraData *extra);
static bool postgresRecheckForeignScan(ForeignScanState *node,
TupleTableSlot *slot);
static void postgresGetForeignUpperPaths(PlannerInfo *root,
UpperRelationKind stage,
RelOptInfo *input_rel,
RelOptInfo *output_rel,
void *extra);
/*
* Helper functions
*/
static void estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *foreignrel,
List *param_join_conds,
List *pathkeys,
PgFdwPathExtraData *fpextra,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost);
static void get_remote_estimate(const char *sql,
PGconn *conn,
double *rows,
int *width,
Cost *startup_cost,
Cost *total_cost);
static void adjust_foreign_grouping_path_cost(PlannerInfo *root,
List *pathkeys,
double retrieved_rows,
double width,
double limit_tuples,
Cost *p_startup_cost,
Cost *p_run_cost);
static bool ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg);
static void create_cursor(ForeignScanState *node);
static void fetch_more_data(ForeignScanState *node);
static void close_cursor(PGconn *conn, unsigned int cursor_number);
static PgFdwModifyState *create_foreign_modify(EState *estate,
RangeTblEntry *rte,
ResultRelInfo *resultRelInfo,
CmdType operation,
Plan *subplan,
char *query,
List *target_attrs,
bool has_returning,
List *retrieved_attrs);
static TupleTableSlot *execute_foreign_modify(EState *estate,
ResultRelInfo *resultRelInfo,
CmdType operation,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void prepare_foreign_modify(PgFdwModifyState *fmstate);
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot);
static void store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res);
static void finish_foreign_modify(PgFdwModifyState *fmstate);
static List *build_remote_returning(Index rtindex, Relation rel,
List *returningList);
static void rebuild_fdw_scan_tlist(ForeignScan *fscan, List *tlist);
static void execute_dml_stmt(ForeignScanState *node);
static TupleTableSlot *get_returning_data(ForeignScanState *node);
static void init_returning_filter(PgFdwDirectModifyState *dmstate,
List *fdw_scan_tlist,
Index rtindex);
static TupleTableSlot *apply_returning_filter(PgFdwDirectModifyState *dmstate,
TupleTableSlot *slot,
EState *estate);
static void prepare_query_params(PlanState *node,
List *fdw_exprs,
int numParams,
FmgrInfo **param_flinfo,
List **param_exprs,
const char ***param_values);
static void process_query_params(ExprContext *econtext,
FmgrInfo *param_flinfo,
List *param_exprs,
const char **param_values);
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows);
static void analyze_row_processor(PGresult *res, int row,
PgFdwAnalyzeState *astate);
static HeapTuple make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
ForeignScanState *fsstate,
MemoryContext temp_context);
static void conversion_error_callback(void *arg);
static bool foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel,
JoinType jointype, RelOptInfo *outerrel, RelOptInfo *innerrel,
JoinPathExtraData *extra);
static bool foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel,
Node *havingQual);
static List *get_useful_pathkeys_for_relation(PlannerInfo *root,
RelOptInfo *rel);
static List *get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel);
static void add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
Path *epq_path);
static void add_foreign_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *grouped_rel,
GroupPathExtraData *extra);
static void add_foreign_ordered_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *ordered_rel);
static void add_foreign_final_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *final_rel,
FinalPathExtraData *extra);
static void apply_server_options(PgFdwRelationInfo *fpinfo);
static void apply_table_options(PgFdwRelationInfo *fpinfo);
static void merge_fdw_options(PgFdwRelationInfo *fpinfo,
const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum
postgres_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = postgresGetForeignRelSize;
routine->GetForeignPaths = postgresGetForeignPaths;
routine->GetForeignPlan = postgresGetForeignPlan;
routine->BeginForeignScan = postgresBeginForeignScan;
routine->IterateForeignScan = postgresIterateForeignScan;
routine->ReScanForeignScan = postgresReScanForeignScan;
routine->EndForeignScan = postgresEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = postgresAddForeignUpdateTargets;
routine->PlanForeignModify = postgresPlanForeignModify;
routine->BeginForeignModify = postgresBeginForeignModify;
routine->ExecForeignInsert = postgresExecForeignInsert;
routine->ExecForeignUpdate = postgresExecForeignUpdate;
routine->ExecForeignDelete = postgresExecForeignDelete;
routine->EndForeignModify = postgresEndForeignModify;
routine->BeginForeignInsert = postgresBeginForeignInsert;
routine->EndForeignInsert = postgresEndForeignInsert;
routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
routine->PlanDirectModify = postgresPlanDirectModify;
routine->BeginDirectModify = postgresBeginDirectModify;
routine->IterateDirectModify = postgresIterateDirectModify;
routine->EndDirectModify = postgresEndDirectModify;
/* Function for EvalPlanQual rechecks */
routine->RecheckForeignScan = postgresRecheckForeignScan;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = postgresExplainForeignScan;
routine->ExplainForeignModify = postgresExplainForeignModify;
routine->ExplainDirectModify = postgresExplainDirectModify;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = postgresAnalyzeForeignTable;
/* Support functions for IMPORT FOREIGN SCHEMA */
routine->ImportForeignSchema = postgresImportForeignSchema;
/* Support functions for join push-down */
routine->GetForeignJoinPaths = postgresGetForeignJoinPaths;
/* Support functions for upper relation push-down */
routine->GetForeignUpperPaths = postgresGetForeignUpperPaths;
PG_RETURN_POINTER(routine);
}
/*
* postgresGetForeignRelSize
* Estimate # of rows and width of the result of the scan
*
* We should consider the effect of all baserestrictinfo clauses here, but
* not any join clauses.
*/
static void
postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo;
ListCell *lc;
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
const char *namespace;
const char *relname;
const char *refname;
/*
* We use PgFdwRelationInfo to pass various information to subsequent
* functions.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
baserel->fdw_private = (void *) fpinfo;
/* Base foreign tables need to be pushed down always. */
fpinfo->pushdown_safe = true;
/* Look up foreign-table catalog info. */
fpinfo->table = GetForeignTable(foreigntableid);
fpinfo->server = GetForeignServer(fpinfo->table->serverid);
/*
* Extract user-settable option values. Note that per-table setting of
* use_remote_estimate overrides per-server setting.
*/
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
fpinfo->shippable_extensions = NIL;
fpinfo->fetch_size = 100;
apply_server_options(fpinfo);
apply_table_options(fpinfo);
/*
* If the table or the server is configured to use remote estimates,
* identify which user to do remote access as during planning. This
* should match what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway.
*/
if (fpinfo->use_remote_estimate)
{
Oid userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
}
else
fpinfo->user = NULL;
/*
* Identify which baserestrictinfo clauses can be sent to the remote
* server and which can't.
*/
classifyConditions(root, baserel, baserel->baserestrictinfo,
&fpinfo->remote_conds, &fpinfo->local_conds);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds. (Note: if we end up using a
* parameterized scan, it's possible that some of the join clauses will be
* sent to the remote and thus we wouldn't really need to retrieve the
* columns used in them. Doesn't seem worth detecting that case though.)
*/
fpinfo->attrs_used = NULL;
pull_varattnos((Node *) baserel->reltarget->exprs, baserel->relid,
&fpinfo->attrs_used);
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&fpinfo->attrs_used);
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
baserel->relid,
JOIN_INNER,
NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction clauses, as well as the
* average row width. Otherwise, estimate using whatever statistics we
* have locally, in a way similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
/*
* Get cost/size estimates with help of remote server. Save the
* values in fpinfo so we don't need to do it again to generate the
* basic foreign path.
*/
estimate_path_cost_size(root, baserel, NIL, NIL, NULL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
/* Report estimated baserel size to planner. */
baserel->rows = fpinfo->rows;
baserel->reltarget->width = fpinfo->width;
}
else
{
/*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
if (baserel->pages == 0 && baserel->tuples == 0)
{
baserel->pages = 10;
baserel->tuples =
(10 * BLCKSZ) / (baserel->reltarget->width +
MAXALIGN(SizeofHeapTupleHeader));
}
/* Estimate baserel size as best we can with local statistics. */
set_baserel_size_estimates(root, baserel);
/* Fill in basically-bogus cost estimates for use later. */
estimate_path_cost_size(root, baserel, NIL, NIL, NULL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
}
/*
* Set the name of relation in fpinfo, while we are constructing it here.
* It will be used to build the string describing the join relation in
* EXPLAIN output. We can't know whether VERBOSE option is specified or
* not, so always schema-qualify the foreign table name.
*/
fpinfo->relation_name = makeStringInfo();
namespace = get_namespace_name(get_rel_namespace(foreigntableid));
relname = get_rel_name(foreigntableid);
refname = rte->eref->aliasname;
appendStringInfo(fpinfo->relation_name, "%s.%s",
quote_identifier(namespace),
quote_identifier(relname));
if (*refname && strcmp(refname, relname) != 0)
appendStringInfo(fpinfo->relation_name, " %s",
quote_identifier(rte->eref->aliasname));
/* No outer and inner relations. */
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
fpinfo->lower_subquery_rels = NULL;
/* Set the relation index. */
fpinfo->relation_index = baserel->relid;
}
/*
* get_useful_ecs_for_relation
* Determine which EquivalenceClasses might be involved in useful
* orderings of this relation.
*
* This function is in some respects a mirror image of the core function
* pathkeys_useful_for_merging: for a regular table, we know what indexes
* we have and want to test whether any of them are useful. For a foreign
* table, we don't know what indexes are present on the remote side but
* want to speculate about which ones we'd like to use if they existed.
*
* This function returns a list of potentially-useful equivalence classes,
* but it does not guarantee that an EquivalenceMember exists which contains
* Vars only from the given relation. For example, given ft1 JOIN t1 ON
* ft1.x + t1.x = 0, this function will say that the equivalence class
* containing ft1.x + t1.x is potentially useful. Supposing ft1 is remote and
* t1 is local (or on a different server), it will turn out that no useful
* ORDER BY clause can be generated. It's not our job to figure that out
* here; we're only interested in identifying relevant ECs.
*/
static List *
get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_eclass_list = NIL;
ListCell *lc;
Relids relids;
/*
* First, consider whether any active EC is potentially useful for a merge
* join against this relation.
*/
if (rel->has_eclass_joins)
{
foreach(lc, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc);
if (eclass_useful_for_merging(root, cur_ec, rel))
useful_eclass_list = lappend(useful_eclass_list, cur_ec);
}
}
/*
* Next, consider whether there are any non-EC derivable join clauses that
* are merge-joinable. If the joininfo list is empty, we can exit
* quickly.
*/
if (rel->joininfo == NIL)
return useful_eclass_list;
/* If this is a child rel, we must use the topmost parent rel to search. */
if (IS_OTHER_REL(rel))
{
Assert(!bms_is_empty(rel->top_parent_relids));
relids = rel->top_parent_relids;
}
else
relids = rel->relids;
/* Check each join clause in turn. */
foreach(lc, rel->joininfo)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
/* Consider only mergejoinable clauses */
if (restrictinfo->mergeopfamilies == NIL)
continue;
/* Make sure we've got canonical ECs. */
update_mergeclause_eclasses(root, restrictinfo);
/*
* restrictinfo->mergeopfamilies != NIL is sufficient to guarantee
* that left_ec and right_ec will be initialized, per comments in
* distribute_qual_to_rels.
*
* We want to identify which side of this merge-joinable clause
* contains columns from the relation produced by this RelOptInfo. We
* test for overlap, not containment, because there could be extra
* relations on either side. For example, suppose we've got something
* like ((A JOIN B ON A.x = B.x) JOIN C ON A.y = C.y) LEFT JOIN D ON
* A.y = D.y. The input rel might be the joinrel between A and B, and
* we'll consider the join clause A.y = D.y. relids contains a
* relation not involved in the join class (B) and the equivalence
* class for the left-hand side of the clause contains a relation not
* involved in the input rel (C). Despite the fact that we have only
* overlap and not containment in either direction, A.y is potentially
* useful as a sort column.
*
* Note that it's even possible that relids overlaps neither side of
* the join clause. For example, consider A LEFT JOIN B ON A.x = B.x
* AND A.x = 1. The clause A.x = 1 will appear in B's joininfo list,
* but overlaps neither side of B. In that case, we just skip this
* join clause, since it doesn't suggest a useful sort order for this
* relation.
*/
if (bms_overlap(relids, restrictinfo->right_ec->ec_relids))
useful_eclass_list = list_append_unique_ptr(useful_eclass_list,
restrictinfo->right_ec);
else if (bms_overlap(relids, restrictinfo->left_ec->ec_relids))
useful_eclass_list = list_append_unique_ptr(useful_eclass_list,
restrictinfo->left_ec);
}
return useful_eclass_list;
}
/*
* get_useful_pathkeys_for_relation
* Determine which orderings of a relation might be useful.
*
* Getting data in sorted order can be useful either because the requested
* order matches the final output ordering for the overall query we're
* planning, or because it enables an efficient merge join. Here, we try
* to figure out which pathkeys to consider.
*/
static List *
get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_pathkeys_list = NIL;
List *useful_eclass_list;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) rel->fdw_private;
EquivalenceClass *query_ec = NULL;
ListCell *lc;
/*
* Pushing the query_pathkeys to the remote server is always worth
* considering, because it might let us avoid a local sort.
*/
fpinfo->qp_is_pushdown_safe = false;
if (root->query_pathkeys)
{
bool query_pathkeys_ok = true;
foreach(lc, root->query_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
Expr *em_expr;
/*
* The planner and executor don't have any clever strategy for
* taking data sorted by a prefix of the query's pathkeys and
* getting it to be sorted by all of those pathkeys. We'll just
* end up resorting the entire data set. So, unless we can push
* down all of the query pathkeys, forget it.
*
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
if (pathkey_ec->ec_has_volatile ||
!(em_expr = find_em_expr_for_rel(pathkey_ec, rel)) ||
!is_foreign_expr(root, rel, em_expr))
{
query_pathkeys_ok = false;
break;
}
}
if (query_pathkeys_ok)
{
useful_pathkeys_list = list_make1(list_copy(root->query_pathkeys));
fpinfo->qp_is_pushdown_safe = true;
}
}
/*
* Even if we're not using remote estimates, having the remote side do the
* sort generally won't be any worse than doing it locally, and it might
* be much better if the remote side can generate data in the right order
* without needing a sort at all. However, what we're going to do next is
* try to generate pathkeys that seem promising for possible merge joins,
* and that's more speculative. A wrong choice might hurt quite a bit, so
* bail out if we can't use remote estimates.
*/
if (!fpinfo->use_remote_estimate)
return useful_pathkeys_list;
/* Get the list of interesting EquivalenceClasses. */
useful_eclass_list = get_useful_ecs_for_relation(root, rel);
/* Extract unique EC for query, if any, so we don't consider it again. */
if (list_length(root->query_pathkeys) == 1)
{
PathKey *query_pathkey = linitial(root->query_pathkeys);
query_ec = query_pathkey->pk_eclass;
}
/*
* As a heuristic, the only pathkeys we consider here are those of length
* one. It's surely possible to consider more, but since each one we
* choose to consider will generate a round-trip to the remote side, we
* need to be a bit cautious here. It would sure be nice to have a local
* cache of information about remote index definitions...
*/
foreach(lc, useful_eclass_list)
{
EquivalenceClass *cur_ec = lfirst(lc);
Expr *em_expr;
PathKey *pathkey;
/* If redundant with what we did above, skip it. */
if (cur_ec == query_ec)
continue;
/* If no pushable expression for this rel, skip it. */
em_expr = find_em_expr_for_rel(cur_ec, rel);
if (em_expr == NULL || !is_foreign_expr(root, rel, em_expr))
continue;
/* Looks like we can generate a pathkey, so let's do it. */
pathkey = make_canonical_pathkey(root, cur_ec,
linitial_oid(cur_ec->ec_opfamilies),
BTLessStrategyNumber,
false);
useful_pathkeys_list = lappend(useful_pathkeys_list,
list_make1(pathkey));
}
return useful_pathkeys_list;
}
/*
* postgresGetForeignPaths
* Create possible scan paths for a scan on the foreign table
*/
static void
postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
ForeignPath *path;
List *ppi_list;
ListCell *lc;
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there). We already did all the work
* to estimate cost and size of this path.
*
* Although this path uses no join clauses, it could still have required
* parameterization due to LATERAL refs in its tlist.
*/
path = create_foreignscan_path(root, baserel,
NULL, /* default pathtarget */
fpinfo->rows,
fpinfo->startup_cost,
fpinfo->total_cost,
NIL, /* no pathkeys */
baserel->lateral_relids,
NULL, /* no extra plan */
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
/* Add paths with pathkeys */
add_paths_with_pathkeys_for_rel(root, baserel, NULL);
/*
* If we're not using remote estimates, stop here. We have no way to
* estimate whether any join clauses would be worth sending across, so
* don't bother building parameterized paths.
*/
if (!fpinfo->use_remote_estimate)
return;
/*
* Thumb through all join clauses for the rel to identify which outer
* relations could supply one or more safe-to-send-to-remote join clauses.
* We'll build a parameterized path for each such outer relation.
*
* It's convenient to manage this by representing each candidate outer
* relation by the ParamPathInfo node for it. We can then use the
* ppi_clauses list in the ParamPathInfo node directly as a list of the
* interesting join clauses for that rel. This takes care of the
* possibility that there are multiple safe join clauses for such a rel,
* and also ensures that we account for unsafe join clauses that we'll
* still have to enforce locally (since the parameterized-path machinery
* insists that we handle all movable clauses).
*/
ppi_list = NIL;
foreach(lc, baserel->joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
/* We do not want the foreign rel itself listed in required_outer */
required_outer = bms_del_member(required_outer, baserel->relid);
/*
* required_outer probably can't be empty here, but if it were, we
* couldn't make a parameterized path.
*/
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/*
* Add it to list unless we already have it. Testing pointer equality
* is OK since get_baserel_parampathinfo won't make duplicates.
*/
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/*
* The above scan examined only "generic" join clauses, not those that
* were absorbed into EquivalenceClauses. See if we can make anything out
* of EquivalenceClauses.
*/
if (baserel->has_eclass_joins)
{
/*
* We repeatedly scan the eclass list looking for column references
* (or expressions) belonging to the foreign rel. Each time we find
* one, we generate a list of equivalence joinclauses for it, and then
* see if any are safe to send to the remote. Repeat till there are
* no more candidate EC members.
*/
ec_member_foreign_arg arg;
arg.already_used = NIL;
for (;;)
{
List *clauses;
/* Make clauses, skipping any that join to lateral_referencers */
arg.current = NULL;
clauses = generate_implied_equalities_for_column(root,
baserel,
ec_member_matches_foreign,
(void *) &arg,
baserel->lateral_referencers);
/* Done if there are no more expressions in the foreign rel */
if (arg.current == NULL)
{
Assert(clauses == NIL);
break;
}
/* Scan the extracted join clauses */
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
required_outer = bms_del_member(required_outer, baserel->relid);
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/* Add it to list unless we already have it */
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/* Try again, now ignoring the expression we found this time */
arg.already_used = lappend(arg.already_used, arg.current);
}
}
/*
* Now build a path for each useful outer relation.
*/
foreach(lc, ppi_list)
{
ParamPathInfo *param_info = (ParamPathInfo *) lfirst(lc);
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Get a cost estimate from the remote */
estimate_path_cost_size(root, baserel,
param_info->ppi_clauses, NIL, NULL,
&rows, &width,
&startup_cost, &total_cost);
/*
* ppi_rows currently won't get looked at by anything, but still we
* may as well ensure that it matches our idea of the rowcount.
*/
param_info->ppi_rows = rows;
/* Make the path */
path = create_foreignscan_path(root, baserel,
NULL, /* default pathtarget */
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
param_info->ppi_req_outer,
NULL,
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
}
}
/*
* postgresGetForeignPlan
* Create ForeignScan plan node which implements selected best path
*/
static ForeignScan *
postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *foreignrel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
Index scan_relid;
List *fdw_private;
List *remote_exprs = NIL;
List *local_exprs = NIL;
List *params_list = NIL;
List *fdw_scan_tlist = NIL;
List *fdw_recheck_quals = NIL;
List *retrieved_attrs;
StringInfoData sql;
bool has_final_sort = false;
bool has_limit = false;
ListCell *lc;
/*
* Get FDW private data created by postgresGetForeignUpperPaths(), if any.
*/
if (best_path->fdw_private)
{
has_final_sort = intVal(list_nth(best_path->fdw_private,
FdwPathPrivateHasFinalSort));
has_limit = intVal(list_nth(best_path->fdw_private,
FdwPathPrivateHasLimit));
}
if (IS_SIMPLE_REL(foreignrel))
{
/*
* For base relations, set scan_relid as the relid of the relation.
*/
scan_relid = foreignrel->relid;
/*
* In a base-relation scan, we must apply the given scan_clauses.
*
* Separate the scan_clauses into those that can be executed remotely
* and those that can't. baserestrictinfo clauses that were
* previously determined to be safe or unsafe by classifyConditions
* are found in fpinfo->remote_conds and fpinfo->local_conds. Anything
* else in the scan_clauses list will be a join clause, which we have
* to check for remote-safety.
*
* Note: the join clauses we see here should be the exact same ones
* previously examined by postgresGetForeignPaths. Possibly it'd be
* worth passing forward the classification work done then, rather
* than repeating it here.
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local
* execution.
*/
foreach(lc, scan_clauses)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
/* Ignore any pseudoconstants, they're dealt with elsewhere */
if (rinfo->pseudoconstant)
continue;
if (list_member_ptr(fpinfo->remote_conds, rinfo))
remote_exprs = lappend(remote_exprs, rinfo->clause);
else if (list_member_ptr(fpinfo->local_conds, rinfo))
local_exprs = lappend(local_exprs, rinfo->clause);
else if (is_foreign_expr(root, foreignrel, rinfo->clause))
remote_exprs = lappend(remote_exprs, rinfo->clause);
else
local_exprs = lappend(local_exprs, rinfo->clause);
}
/*
* For a base-relation scan, we have to support EPQ recheck, which
* should recheck all the remote quals.
*/
fdw_recheck_quals = remote_exprs;
}
else
{
/*
* Join relation or upper relation - set scan_relid to 0.
*/
scan_relid = 0;
/*
* For a join rel, baserestrictinfo is NIL and we are not considering
* parameterization right now, so there should be no scan_clauses for
* a joinrel or an upper rel either.
*/
Assert(!scan_clauses);
/*
* Instead we get the conditions to apply from the fdw_private
* structure.
*/
remote_exprs = extract_actual_clauses(fpinfo->remote_conds, false);
local_exprs = extract_actual_clauses(fpinfo->local_conds, false);
/*
* We leave fdw_recheck_quals empty in this case, since we never need
* to apply EPQ recheck clauses. In the case of a joinrel, EPQ
* recheck is handled elsewhere --- see postgresGetForeignJoinPaths().
* If we're planning an upperrel (ie, remote grouping or aggregation)
* then there's no EPQ to do because SELECT FOR UPDATE wouldn't be
* allowed, and indeed we *can't* put the remote clauses into
* fdw_recheck_quals because the unaggregated Vars won't be available
* locally.
*/
/* Build the list of columns to be fetched from the foreign server. */
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
/*
* Ensure that the outer plan produces a tuple whose descriptor
* matches our scan tuple slot. Also, remove the local conditions
* from outer plan's quals, lest they be evaluated twice, once by the
* local plan and once by the scan.
*/
if (outer_plan)
{
ListCell *lc;
/*
* Right now, we only consider grouping and aggregation beyond
* joins. Queries involving aggregates or grouping do not require
* EPQ mechanism, hence should not have an outer plan here.
*/
Assert(!IS_UPPER_REL(foreignrel));
/*
* First, update the plan's qual list if possible. In some cases
* the quals might be enforced below the topmost plan level, in
* which case we'll fail to remove them; it's not worth working
* harder than this.
*/
foreach(lc, local_exprs)
{
Node *qual = lfirst(lc);
outer_plan->qual = list_delete(outer_plan->qual, qual);
/*
* For an inner join the local conditions of foreign scan plan
* can be part of the joinquals as well. (They might also be
* in the mergequals or hashquals, but we can't touch those
* without breaking the plan.)
*/
if (IsA(outer_plan, NestLoop) ||
IsA(outer_plan, MergeJoin) ||
IsA(outer_plan, HashJoin))
{
Join *join_plan = (Join *) outer_plan;
if (join_plan->jointype == JOIN_INNER)
join_plan->joinqual = list_delete(join_plan->joinqual,
qual);
}
}
/*
* Now fix the subplan's tlist --- this might result in inserting
* a Result node atop the plan tree.
*/
outer_plan = change_plan_targetlist(outer_plan, fdw_scan_tlist,
best_path->path.parallel_safe);
}
}
/*
* Build the query string to be sent for execution, and identify
* expressions to be sent as parameters.
*/
initStringInfo(&sql);
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist,
remote_exprs, best_path->path.pathkeys,
has_final_sort, has_limit, false,
&retrieved_attrs, &params_list);
/* Remember remote_exprs for possible use by postgresPlanDirectModify */
fpinfo->final_remote_exprs = remote_exprs;
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match order in enum FdwScanPrivateIndex.
*/
fdw_private = list_make3(makeString(sql.data),
retrieved_attrs,
makeInteger(fpinfo->fetch_size));
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel))
fdw_private = lappend(fdw_private,
makeString(fpinfo->relation_name->data));
/*
* Create the ForeignScan node for the given relation.
*
* Note that the remote parameter expressions are stored in the fdw_exprs
* field of the finished plan node; we can't keep them in private state
* because then they wouldn't be subject to later planner processing.
*/
return make_foreignscan(tlist,
local_exprs,
scan_relid,
params_list,
fdw_private,
fdw_scan_tlist,
fdw_recheck_quals,
outer_plan);
}
/*
* postgresBeginForeignScan
* Initiate an executor scan of a foreign PostgreSQL table.
*/
static void
postgresBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwScanState *fsstate;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
UserMapping *user;
int rtindex;
int numParams;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (PgFdwScanState *) palloc0(sizeof(PgFdwScanState));
node->fdw_state = (void *) fsstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does. In case of a join or aggregate, use the
* lowest-numbered member RTE as a representative; we would get the same
* result from any.
*/
if (fsplan->scan.scanrelid > 0)
rtindex = fsplan->scan.scanrelid;
else
rtindex = bms_next_member(fsplan->fs_relids, -1);
rte = exec_rt_fetch(rtindex, estate);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(rte->relid);
user = GetUserMapping(userid, table->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
fsstate->conn = GetConnection(user, false);
/* Assign a unique ID for my cursor */
fsstate->cursor_number = GetCursorNumber(fsstate->conn);
fsstate->cursor_exists = false;
/* Get private info created by planner functions. */
fsstate->query = strVal(list_nth(fsplan->fdw_private,
FdwScanPrivateSelectSql));
fsstate->retrieved_attrs = (List *) list_nth(fsplan->fdw_private,
FdwScanPrivateRetrievedAttrs);
fsstate->fetch_size = intVal(list_nth(fsplan->fdw_private,
FdwScanPrivateFetchSize));
/* Create contexts for batches of tuples and per-tuple temp workspace. */
fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw tuple data",
ALLOCSET_DEFAULT_SIZES);
fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/*
* Get info we'll need for converting data fetched from the foreign server
* into local representation and error reporting during that process.
*/
if (fsplan->scan.scanrelid > 0)
{
fsstate->rel = node->ss.ss_currentRelation;
fsstate->tupdesc = RelationGetDescr(fsstate->rel);
}
else
{
fsstate->rel = NULL;
fsstate->tupdesc = node->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
}
fsstate->attinmeta = TupleDescGetAttInMetadata(fsstate->tupdesc);
/*
* Prepare for processing of parameters used in remote query, if any.
*/
numParams = list_length(fsplan->fdw_exprs);
fsstate->numParams = numParams;
if (numParams > 0)
prepare_query_params((PlanState *) node,
fsplan->fdw_exprs,
numParams,
&fsstate->param_flinfo,
&fsstate->param_exprs,
&fsstate->param_values);
}
/*
* postgresIterateForeignScan
* Retrieve next row from the result set, or clear tuple slot to indicate
* EOF.
*/
static TupleTableSlot *
postgresIterateForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If this is the first call after Begin or ReScan, we need to create the
* cursor on the remote side.
*/
if (!fsstate->cursor_exists)
create_cursor(node);
/*
* Get some more tuples, if we've run out.
*/
if (fsstate->next_tuple >= fsstate->num_tuples)
{
/* No point in another fetch if we already detected EOF, though. */
if (!fsstate->eof_reached)
fetch_more_data(node);
/* If we didn't get any tuples, must be end of data. */
if (fsstate->next_tuple >= fsstate->num_tuples)
return ExecClearTuple(slot);
}
/*
* Return the next tuple.
*/
ExecStoreHeapTuple(fsstate->tuples[fsstate->next_tuple++],
slot,
false);
return slot;
}
/*
* postgresReScanForeignScan
* Restart the scan.
*/
static void
postgresReScanForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
char sql[64];
PGresult *res;
/* If we haven't created the cursor yet, nothing to do. */
if (!fsstate->cursor_exists)
return;
/*
* If any internal parameters affecting this node have changed, we'd
* better destroy and recreate the cursor. Otherwise, rewinding it should
* be good enough. If we've only fetched zero or one batch, we needn't
* even rewind the cursor, just rescan what we have.
*/
if (node->ss.ps.chgParam != NULL)
{
fsstate->cursor_exists = false;
snprintf(sql, sizeof(sql), "CLOSE c%u",
fsstate->cursor_number);
}
else if (fsstate->fetch_ct_2 > 1)
{
snprintf(sql, sizeof(sql), "MOVE BACKWARD ALL IN c%u",
fsstate->cursor_number);
}
else
{
/* Easy: just rescan what we already have in memory, if anything */
fsstate->next_tuple = 0;
return;
}
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(fsstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fsstate->conn, true, sql);
PQclear(res);
/* Now force a fresh FETCH. */
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
}
/*
* postgresEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void
postgresEndForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
/* if fsstate is NULL, we are in EXPLAIN; nothing to do */
if (fsstate == NULL)
return;
/* Close the cursor if open, to prevent accumulation of cursors */
if (fsstate->cursor_exists)
close_cursor(fsstate->conn, fsstate->cursor_number);
/* Release remote connection */
ReleaseConnection(fsstate->conn);
fsstate->conn = NULL;
/* MemoryContexts will be deleted automatically. */
}
/*
* postgresAddForeignUpdateTargets
* Add resjunk column(s) needed for update/delete on a foreign table
*/
static void
postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation)
{
Var *var;
const char *attrname;
TargetEntry *tle;
/*
* In postgres_fdw, what we need is the ctid, same as for a regular table.
*/
/* Make a Var representing the desired value */
var = makeVar(parsetree->resultRelation,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
InvalidOid,
0);
/* Wrap it in a resjunk TLE with the right name ... */
attrname = "ctid";
tle = makeTargetEntry((Expr *) var,
list_length(parsetree->targetList) + 1,
pstrdup(attrname),
true);
/* ... and add it to the query's targetlist */
parsetree->targetList = lappend(parsetree->targetList, tle);
}
/*
* postgresPlanForeignModify
* Plan an insert/update/delete operation on a foreign table
*/
static List *
postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
RangeTblEntry *rte = planner_rt_fetch(resultRelation, root);
Relation rel;
StringInfoData sql;
List *targetAttrs = NIL;
List *withCheckOptionList = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
bool doNothing = false;
initStringInfo(&sql);
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
rel = table_open(rte->relid, NoLock);
/*
* In an INSERT, we transmit all columns that are defined in the foreign
* table. In an UPDATE, if there are BEFORE ROW UPDATE triggers on the
* foreign table, we transmit all columns like INSERT; else we transmit
* only columns that were explicitly targets of the UPDATE, so as to avoid
* unnecessary data transmission. (We can't do that for INSERT since we
* would miss sending default values for columns not listed in the source
* statement, and for UPDATE if there are BEFORE ROW UPDATE triggers since
* those triggers might change values for non-target columns, in which
* case we would miss sending changed values for those columns.)
*/
if (operation == CMD_INSERT ||
(operation == CMD_UPDATE &&
rel->trigdesc &&
rel->trigdesc->trig_update_before_row))
{
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
for (attnum = 1; attnum <= tupdesc->natts; attnum++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
if (!attr->attisdropped)
targetAttrs = lappend_int(targetAttrs, attnum);
}
}
else if (operation == CMD_UPDATE)
{
int col;
Bitmapset *allUpdatedCols = bms_union(rte->updatedCols, rte->extraUpdatedCols);
col = -1;
while ((col = bms_next_member(allUpdatedCols, col)) >= 0)
{
/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
AttrNumber attno = col + FirstLowInvalidHeapAttributeNumber;
if (attno <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
targetAttrs = lappend_int(targetAttrs, attno);
}
}
/*
* Extract the relevant WITH CHECK OPTION list if any.
*/
if (plan->withCheckOptionLists)
withCheckOptionList = (List *) list_nth(plan->withCheckOptionLists,
subplan_index);
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* ON CONFLICT DO UPDATE and DO NOTHING case with inference specification
* should have already been rejected in the optimizer, as presently there
* is no way to recognize an arbiter index on a foreign table. Only DO
* NOTHING is supported without an inference specification.
*/
if (plan->onConflictAction == ONCONFLICT_NOTHING)
doNothing = true;
else if (plan->onConflictAction != ONCONFLICT_NONE)
elog(ERROR, "unexpected ON CONFLICT specification: %d",
(int) plan->onConflictAction);
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_INSERT:
deparseInsertSql(&sql, rte, resultRelation, rel,
targetAttrs, doNothing,
withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_UPDATE:
deparseUpdateSql(&sql, rte, resultRelation, rel,
targetAttrs,
withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_DELETE:
deparseDeleteSql(&sql, rte, resultRelation, rel,
returningList,
&retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
table_close(rel, NoLock);
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwModifyPrivateIndex, above.
*/
return list_make4(makeString(sql.data),
targetAttrs,
makeInteger((retrieved_attrs != NIL)),
retrieved_attrs);
}
/*
* postgresBeginForeignModify
* Begin an insert/update/delete operation on a foreign table
*/
static void
postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags)
{
PgFdwModifyState *fmstate;
char *query;
List *target_attrs;
bool has_returning;
List *retrieved_attrs;
RangeTblEntry *rte;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. resultRelInfo->ri_FdwState
* stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/* Deconstruct fdw_private data. */
query = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
target_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateTargetAttnums);
has_returning = intVal(list_nth(fdw_private,
FdwModifyPrivateHasReturning));
retrieved_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateRetrievedAttrs);
/* Find RTE. */
rte = exec_rt_fetch(resultRelInfo->ri_RangeTableIndex,
mtstate->ps.state);
/* Construct an execution state. */
fmstate = create_foreign_modify(mtstate->ps.state,
rte,
resultRelInfo,
mtstate->operation,
mtstate->mt_plans[subplan_index]->plan,
query,
target_attrs,
has_returning,
retrieved_attrs);
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresExecForeignInsert
* Insert one row into a foreign table
*/
static TupleTableSlot *
postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
TupleTableSlot *rslot;
/*
* If the fmstate has aux_fmstate set, use the aux_fmstate (see
* postgresBeginForeignInsert())
*/
if (fmstate->aux_fmstate)
resultRelInfo->ri_FdwState = fmstate->aux_fmstate;
rslot = execute_foreign_modify(estate, resultRelInfo, CMD_INSERT,
slot, planSlot);
/* Revert that change */
if (fmstate->aux_fmstate)
resultRelInfo->ri_FdwState = fmstate;
return rslot;
}
/*
* postgresExecForeignUpdate
* Update one row in a foreign table
*/
static TupleTableSlot *
postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
return execute_foreign_modify(estate, resultRelInfo, CMD_UPDATE,
slot, planSlot);
}
/*
* postgresExecForeignDelete
* Delete one row from a foreign table
*/
static TupleTableSlot *
postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
return execute_foreign_modify(estate, resultRelInfo, CMD_DELETE,
slot, planSlot);
}
/*
* postgresEndForeignModify
* Finish an insert/update/delete operation on a foreign table
*/
static void
postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
/* If fmstate is NULL, we are in EXPLAIN; nothing to do */
if (fmstate == NULL)
return;
/* Destroy the execution state */
finish_foreign_modify(fmstate);
}
/*
* postgresBeginForeignInsert
* Begin an insert operation on a foreign table
*/
static void
postgresBeginForeignInsert(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate;
ModifyTable *plan = castNode(ModifyTable, mtstate->ps.plan);
EState *estate = mtstate->ps.state;
Index resultRelation = resultRelInfo->ri_RangeTableIndex;
Relation rel = resultRelInfo->ri_RelationDesc;
RangeTblEntry *rte;
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
StringInfoData sql;
List *targetAttrs = NIL;
List *retrieved_attrs = NIL;
bool doNothing = false;
/*
* If the foreign table we are about to insert routed rows into is also an
* UPDATE subplan result rel that will be updated later, proceeding with
* the INSERT will result in the later UPDATE incorrectly modifying those
* routed rows, so prevent the INSERT --- it would be nice if we could
* handle this case; but for now, throw an error for safety.
*/
if (plan && plan->operation == CMD_UPDATE &&
(resultRelInfo->ri_usesFdwDirectModify ||
resultRelInfo->ri_FdwState) &&
resultRelInfo > mtstate->resultRelInfo + mtstate->mt_whichplan)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot route tuples into foreign table to be updated \"%s\"",
RelationGetRelationName(rel))));
initStringInfo(&sql);
/* We transmit all columns that are defined in the foreign table. */
for (attnum = 1; attnum <= tupdesc->natts; attnum++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
if (!attr->attisdropped)
targetAttrs = lappend_int(targetAttrs, attnum);
}
/* Check if we add the ON CONFLICT clause to the remote query. */
if (plan)
{
OnConflictAction onConflictAction = plan->onConflictAction;
/* We only support DO NOTHING without an inference specification. */
if (onConflictAction == ONCONFLICT_NOTHING)
doNothing = true;
else if (onConflictAction != ONCONFLICT_NONE)
elog(ERROR, "unexpected ON CONFLICT specification: %d",
(int) onConflictAction);
}
/*
* If the foreign table is a partition, we need to create a new RTE
* describing the foreign table for use by deparseInsertSql and
* create_foreign_modify() below, after first copying the parent's RTE and
* modifying some fields to describe the foreign partition to work on.
* However, if this is invoked by UPDATE, the existing RTE may already
* correspond to this partition if it is one of the UPDATE subplan target
* rels; in that case, we can just use the existing RTE as-is.
*/
rte = exec_rt_fetch(resultRelation, estate);
if (rte->relid != RelationGetRelid(rel))
{
rte = copyObject(rte);
rte->relid = RelationGetRelid(rel);
rte->relkind = RELKIND_FOREIGN_TABLE;
/*
* For UPDATE, we must use the RT index of the first subplan target
* rel's RTE, because the core code would have built expressions for
* the partition, such as RETURNING, using that RT index as varno of
* Vars contained in those expressions.
*/
if (plan && plan->operation == CMD_UPDATE &&
resultRelation == plan->rootRelation)
resultRelation = mtstate->resultRelInfo[0].ri_RangeTableIndex;
}
/* Construct the SQL command string. */
deparseInsertSql(&sql, rte, resultRelation, rel, targetAttrs, doNothing,
resultRelInfo->ri_WithCheckOptions,
resultRelInfo->ri_returningList,
&retrieved_attrs);
/* Construct an execution state. */
fmstate = create_foreign_modify(mtstate->ps.state,
rte,
resultRelInfo,
CMD_INSERT,
NULL,
sql.data,
targetAttrs,
retrieved_attrs != NIL,
retrieved_attrs);
/*
* If the given resultRelInfo already has PgFdwModifyState set, it means
* the foreign table is an UPDATE subplan result rel; in which case, store
* the resulting state into the aux_fmstate of the PgFdwModifyState.
*/
if (resultRelInfo->ri_FdwState)
{
Assert(plan && plan->operation == CMD_UPDATE);
Assert(resultRelInfo->ri_usesFdwDirectModify == false);
((PgFdwModifyState *) resultRelInfo->ri_FdwState)->aux_fmstate = fmstate;
}
else
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresEndForeignInsert
* Finish an insert operation on a foreign table
*/
static void
postgresEndForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Assert(fmstate != NULL);
/*
* If the fmstate has aux_fmstate set, get the aux_fmstate (see
* postgresBeginForeignInsert())
*/
if (fmstate->aux_fmstate)
fmstate = fmstate->aux_fmstate;
/* Destroy the execution state */
finish_foreign_modify(fmstate);
}
/*
* postgresIsForeignRelUpdatable
* Determine whether a foreign table supports INSERT, UPDATE and/or
* DELETE.
*/
static int
postgresIsForeignRelUpdatable(Relation rel)
{
bool updatable;
ForeignTable *table;
ForeignServer *server;
ListCell *lc;
/*
* By default, all postgres_fdw foreign tables are assumed updatable. This
* can be overridden by a per-server setting, which in turn can be
* overridden by a per-table setting.
*/
updatable = true;
table = GetForeignTable(RelationGetRelid(rel));
server = GetForeignServer(table->serverid);
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
/*
* Currently "updatable" means support for INSERT, UPDATE and DELETE.
*/
return updatable ?
(1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE) : 0;
}
/*
* postgresRecheckForeignScan
* Execute a local join execution plan for a foreign join
*/
static bool
postgresRecheckForeignScan(ForeignScanState *node, TupleTableSlot *slot)
{
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
PlanState *outerPlan = outerPlanState(node);
TupleTableSlot *result;
/* For base foreign relations, it suffices to set fdw_recheck_quals */
if (scanrelid > 0)
return true;
Assert(outerPlan != NULL);
/* Execute a local join execution plan */
result = ExecProcNode(outerPlan);
if (TupIsNull(result))
return false;
/* Store result in the given slot */
ExecCopySlot(slot, result);
return true;
}
/*
* postgresPlanDirectModify
* Consider a direct foreign table modification
*
* Decide whether it is safe to modify a foreign table directly, and if so,
* rewrite subplan accordingly.
*/
static bool
postgresPlanDirectModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
Plan *subplan;
RelOptInfo *foreignrel;
RangeTblEntry *rte;
PgFdwRelationInfo *fpinfo;
Relation rel;
StringInfoData sql;
ForeignScan *fscan;
List *targetAttrs = NIL;
List *remote_exprs;
List *params_list = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
/*
* Decide whether it is safe to modify a foreign table directly.
*/
/*
* The table modification must be an UPDATE or DELETE.
*/
if (operation != CMD_UPDATE && operation != CMD_DELETE)
return false;
/*
* It's unsafe to modify a foreign table directly if there are any local
* joins needed.
*/
subplan = (Plan *) list_nth(plan->plans, subplan_index);
if (!IsA(subplan, ForeignScan))
return false;
fscan = (ForeignScan *) subplan;
/*
* It's unsafe to modify a foreign table directly if there are any quals
* that should be evaluated locally.
*/
if (subplan->qual != NIL)
return false;
/* Safe to fetch data about the target foreign rel */
if (fscan->scan.scanrelid == 0)
{
foreignrel = find_join_rel(root, fscan->fs_relids);
/* We should have a rel for this foreign join. */
Assert(foreignrel);
}
else
foreignrel = root->simple_rel_array[resultRelation];
rte = root->simple_rte_array[resultRelation];
fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
/*
* It's unsafe to update a foreign table directly, if any expressions to
* assign to the target columns are unsafe to evaluate remotely.
*/
if (operation == CMD_UPDATE)
{
int col;
/*
* We transmit only columns that were explicitly targets of the
* UPDATE, so as to avoid unnecessary data transmission.
*/
col = -1;
while ((col = bms_next_member(rte->updatedCols, col)) >= 0)
{
/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
AttrNumber attno = col + FirstLowInvalidHeapAttributeNumber;
TargetEntry *tle;
if (attno <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
tle = get_tle_by_resno(subplan->targetlist, attno);
if (!tle)
elog(ERROR, "attribute number %d not found in subplan targetlist",
attno);
if (!is_foreign_expr(root, foreignrel, (Expr *) tle->expr))
return false;
targetAttrs = lappend_int(targetAttrs, attno);
}
}
/*
* Ok, rewrite subplan so as to modify the foreign table directly.
*/
initStringInfo(&sql);
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
rel = table_open(rte->relid, NoLock);
/*
* Recall the qual clauses that must be evaluated remotely. (These are
* bare clauses not RestrictInfos, but deparse.c's appendConditions()
* doesn't care.)
*/
remote_exprs = fpinfo->final_remote_exprs;
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
{
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* When performing an UPDATE/DELETE .. RETURNING on a join directly,
* we fetch from the foreign server any Vars specified in RETURNING
* that refer not only to the target relation but to non-target
* relations. So we'll deparse them into the RETURNING clause of the
* remote query; use a targetlist consisting of them instead, which
* will be adjusted to be new fdw_scan_tlist of the foreign-scan plan
* node below.
*/
if (fscan->scan.scanrelid == 0)
returningList = build_remote_returning(resultRelation, rel,
returningList);
}
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_UPDATE:
deparseDirectUpdateSql(&sql, root, resultRelation, rel,
foreignrel,
((Plan *) fscan)->targetlist,
targetAttrs,
remote_exprs, &params_list,
returningList, &retrieved_attrs);
break;
case CMD_DELETE:
deparseDirectDeleteSql(&sql, root, resultRelation, rel,
foreignrel,
remote_exprs, &params_list,
returningList, &retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
/*
* Update the operation info.
*/
fscan->operation = operation;
/*
* Update the fdw_exprs list that will be available to the executor.
*/
fscan->fdw_exprs = params_list;
/*
* Update the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwDirectModifyPrivateIndex, above.
*/
fscan->fdw_private = list_make4(makeString(sql.data),
makeInteger((retrieved_attrs != NIL)),
retrieved_attrs,
makeInteger(plan->canSetTag));
/*
* Update the foreign-join-related fields.
*/
if (fscan->scan.scanrelid == 0)
{
/* No need for the outer subplan. */
fscan->scan.plan.lefttree = NULL;
/* Build new fdw_scan_tlist if UPDATE/DELETE .. RETURNING. */
if (returningList)
rebuild_fdw_scan_tlist(fscan, returningList);
}
table_close(rel, NoLock);
return true;
}
/*
* postgresBeginDirectModify
* Prepare a direct foreign table modification
*/
static void
postgresBeginDirectModify(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwDirectModifyState *dmstate;
Index rtindex;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
UserMapping *user;
int numParams;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
dmstate = (PgFdwDirectModifyState *) palloc0(sizeof(PgFdwDirectModifyState));
node->fdw_state = (void *) dmstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rtindex = estate->es_result_relation_info->ri_RangeTableIndex;
rte = exec_rt_fetch(rtindex, estate);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
if (fsplan->scan.scanrelid == 0)
dmstate->rel = ExecOpenScanRelation(estate, rtindex, eflags);
else
dmstate->rel = node->ss.ss_currentRelation;
table = GetForeignTable(RelationGetRelid(dmstate->rel));
user = GetUserMapping(userid, table->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
dmstate->conn = GetConnection(user, false);
/* Update the foreign-join-related fields. */
if (fsplan->scan.scanrelid == 0)
{
/* Save info about foreign table. */
dmstate->resultRel = dmstate->rel;
/*
* Set dmstate->rel to NULL to teach get_returning_data() and
* make_tuple_from_result_row() that columns fetched from the remote
* server are described by fdw_scan_tlist of the foreign-scan plan
* node, not the tuple descriptor for the target relation.
*/
dmstate->rel = NULL;
}
/* Initialize state variable */
dmstate->num_tuples = -1; /* -1 means not set yet */
/* Get private info created by planner functions. */
dmstate->query = strVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateUpdateSql));
dmstate->has_returning = intVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateHasReturning));
dmstate->retrieved_attrs = (List *) list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateRetrievedAttrs);
dmstate->set_processed = intVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateSetProcessed));
/* Create context for per-tuple temp workspace. */
dmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/* Prepare for input conversion of RETURNING results. */
if (dmstate->has_returning)
{
TupleDesc tupdesc;
if (fsplan->scan.scanrelid == 0)
tupdesc = node->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
else
tupdesc = RelationGetDescr(dmstate->rel);
dmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
/*
* When performing an UPDATE/DELETE .. RETURNING on a join directly,
* initialize a filter to extract an updated/deleted tuple from a scan
* tuple.
*/
if (fsplan->scan.scanrelid == 0)
init_returning_filter(dmstate, fsplan->fdw_scan_tlist, rtindex);
}
/*
* Prepare for processing of parameters used in remote query, if any.
*/
numParams = list_length(fsplan->fdw_exprs);
dmstate->numParams = numParams;
if (numParams > 0)
prepare_query_params((PlanState *) node,
fsplan->fdw_exprs,
numParams,
&dmstate->param_flinfo,
&dmstate->param_exprs,
&dmstate->param_values);
}
/*
* postgresIterateDirectModify
* Execute a direct foreign table modification
*/
static TupleTableSlot *
postgresIterateDirectModify(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
EState *estate = node->ss.ps.state;
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
/*
* If this is the first call after Begin, execute the statement.
*/
if (dmstate->num_tuples == -1)
execute_dml_stmt(node);
/*
* If the local query doesn't specify RETURNING, just clear tuple slot.
*/
if (!resultRelInfo->ri_projectReturning)
{
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
Instrumentation *instr = node->ss.ps.instrument;
Assert(!dmstate->has_returning);
/* Increment the command es_processed count if necessary. */
if (dmstate->set_processed)
estate->es_processed += dmstate->num_tuples;
/* Increment the tuple count for EXPLAIN ANALYZE if necessary. */
if (instr)
instr->tuplecount += dmstate->num_tuples;
return ExecClearTuple(slot);
}
/*
* Get the next RETURNING tuple.
*/
return get_returning_data(node);
}
/*
* postgresEndDirectModify
* Finish a direct foreign table modification
*/
static void
postgresEndDirectModify(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
/* if dmstate is NULL, we are in EXPLAIN; nothing to do */
if (dmstate == NULL)
return;
/* Release PGresult */
if (dmstate->result)
PQclear(dmstate->result);
/* Release remote connection */
ReleaseConnection(dmstate->conn);
dmstate->conn = NULL;
/* MemoryContext will be deleted automatically. */
}
/*
* postgresExplainForeignScan
* Produce extra output for EXPLAIN of a ForeignScan on a foreign table
*/
static void
postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
char *relations;
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
/*
* Add names of relation handled by the foreign scan when the scan is a
* join
*/
if (list_length(fdw_private) > FdwScanPrivateRelations)
{
relations = strVal(list_nth(fdw_private, FdwScanPrivateRelations));
ExplainPropertyText("Relations", relations, es);
}
/*
* Add remote query, when VERBOSE option is specified.
*/
if (es->verbose)
{
sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainForeignModify
* Produce extra output for EXPLAIN of a ModifyTable on a foreign table
*/
static void
postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es)
{
if (es->verbose)
{
char *sql = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainDirectModify
* Produce extra output for EXPLAIN of a ForeignScan that modifies a
* foreign table directly
*/
static void
postgresExplainDirectModify(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
if (es->verbose)
{
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
sql = strVal(list_nth(fdw_private, FdwDirectModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* estimate_path_cost_size
* Get cost and size estimates for a foreign scan on given foreign relation
* either a base relation or a join between foreign relations or an upper
* relation containing foreign relations.
*
* param_join_conds are the parameterization clauses with outer relations.
* pathkeys specify the expected sort order if any for given path being costed.
* fpextra specifies additional post-scan/join-processing steps such as the
* final sort and the LIMIT restriction.
*
* The function returns the cost and size estimates in p_rows, p_width,
* p_startup_cost and p_total_cost variables.
*/
static void
estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *foreignrel,
List *param_join_conds,
List *pathkeys,
PgFdwPathExtraData *fpextra,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
double rows;
double retrieved_rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Make sure the core code has set up the relation's reltarget */
Assert(foreignrel->reltarget);
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction+join clauses. Otherwise,
* estimate rows using whatever statistics we have locally, in a way
* similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
List *remote_param_join_conds;
List *local_param_join_conds;
StringInfoData sql;
PGconn *conn;
Selectivity local_sel;
QualCost local_cost;
List *fdw_scan_tlist = NIL;
List *remote_conds;
/* Required only to be passed to deparseSelectStmtForRel */
List *retrieved_attrs;
/*
* param_join_conds might contain both clauses that are safe to send
* across, and clauses that aren't.
*/
classifyConditions(root, foreignrel, param_join_conds,
&remote_param_join_conds, &local_param_join_conds);
/* Build the list of columns to be fetched from the foreign server. */
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel))
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
else
fdw_scan_tlist = NIL;
/*
* The complete list of remote conditions includes everything from
* baserestrictinfo plus any extra join_conds relevant to this
* particular path.
*/
remote_conds = list_concat(remote_param_join_conds,
fpinfo->remote_conds);
/*
* Construct EXPLAIN query including the desired SELECT, FROM, and
* WHERE clauses. Params and other-relation Vars are replaced by dummy
* values, so don't request params_list.
*/
initStringInfo(&sql);
appendStringInfoString(&sql, "EXPLAIN ");
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist,
remote_conds, pathkeys,
fpextra ? fpextra->has_final_sort : false,
fpextra ? fpextra->has_limit : false,
false, &retrieved_attrs, NULL);
/* Get the remote estimate */
conn = GetConnection(fpinfo->user, false);
get_remote_estimate(sql.data, conn, &rows, &width,
&startup_cost, &total_cost);
ReleaseConnection(conn);
retrieved_rows = rows;
/* Factor in the selectivity of the locally-checked quals */
local_sel = clauselist_selectivity(root,
local_param_join_conds,
foreignrel->relid,
JOIN_INNER,
NULL);
local_sel *= fpinfo->local_conds_sel;
rows = clamp_row_est(rows * local_sel);
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
total_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
cost_qual_eval(&local_cost, local_param_join_conds, root);
startup_cost += local_cost.startup;
total_cost += local_cost.per_tuple * retrieved_rows;
/*
* Add in tlist eval cost for each output row. In case of an
* aggregate, some of the tlist expressions such as grouping
* expressions will be evaluated remotely, so adjust the costs.
*/
startup_cost += foreignrel->reltarget->cost.startup;
total_cost += foreignrel->reltarget->cost.startup;
total_cost += foreignrel->reltarget->cost.per_tuple * rows;
if (IS_UPPER_REL(foreignrel))
{
QualCost tlist_cost;
cost_qual_eval(&tlist_cost, fdw_scan_tlist, root);
startup_cost -= tlist_cost.startup;
total_cost -= tlist_cost.startup;
total_cost -= tlist_cost.per_tuple * rows;
}
}
else
{
Cost run_cost = 0;
/*
* We don't support join conditions in this mode (hence, no
* parameterized paths can be made).
*/
Assert(param_join_conds == NIL);
/*
* We will come here again and again with different set of pathkeys or
* additional post-scan/join-processing steps that caller wants to
* cost. We don't need to calculate the cost/size estimates for the
* underlying scan, join, or grouping each time. Instead, use those
* estimates if we have cached them already.
*/
if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0)
{
Assert(fpinfo->retrieved_rows >= 1);
rows = fpinfo->rows;
retrieved_rows = fpinfo->retrieved_rows;
width = fpinfo->width;
startup_cost = fpinfo->rel_startup_cost;
run_cost = fpinfo->rel_total_cost - fpinfo->rel_startup_cost;
/*
* If we estimate the costs of a foreign scan or a foreign join
* with additional post-scan/join-processing steps, the scan or
* join costs obtained from the cache wouldn't yet contain the
* eval costs for the final scan/join target, which would've been
* updated by apply_scanjoin_target_to_paths(); add the eval costs
* now.
*/
if (fpextra && !IS_UPPER_REL(foreignrel))
{
/* Shouldn't get here unless we have LIMIT */
Assert(fpextra->has_limit);
Assert(foreignrel->reloptkind == RELOPT_BASEREL ||
foreignrel->reloptkind == RELOPT_JOINREL);
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
}
else if (IS_JOIN_REL(foreignrel))
{
PgFdwRelationInfo *fpinfo_i;
PgFdwRelationInfo *fpinfo_o;
QualCost join_cost;
QualCost remote_conds_cost;
double nrows;
/* Use rows/width estimates made by the core code. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/* For join we expect inner and outer relations set */
Assert(fpinfo->innerrel && fpinfo->outerrel);
fpinfo_i = (PgFdwRelationInfo *) fpinfo->innerrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *) fpinfo->outerrel->fdw_private;
/* Estimate of number of rows in cross product */
nrows = fpinfo_i->rows * fpinfo_o->rows;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most nrows.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, nrows);
/*
* The cost of foreign join is estimated as cost of generating
* rows for the joining relations + cost for applying quals on the
* rows.
*/
/*
* Calculate the cost of clauses pushed down to the foreign server
*/
cost_qual_eval(&remote_conds_cost, fpinfo->remote_conds, root);
/* Calculate the cost of applying join clauses */
cost_qual_eval(&join_cost, fpinfo->joinclauses, root);
/*
* Startup cost includes startup cost of joining relations and the
* startup cost for join and other clauses. We do not include the
* startup cost specific to join strategy (e.g. setting up hash
* tables) since we do not know what strategy the foreign server
* is going to use.
*/
startup_cost = fpinfo_i->rel_startup_cost + fpinfo_o->rel_startup_cost;
startup_cost += join_cost.startup;
startup_cost += remote_conds_cost.startup;
startup_cost += fpinfo->local_conds_cost.startup;
/*
* Run time cost includes:
*
* 1. Run time cost (total_cost - startup_cost) of relations being
* joined
*
* 2. Run time cost of applying join clauses on the cross product
* of the joining relations.
*
* 3. Run time cost of applying pushed down other clauses on the
* result of join
*
* 4. Run time cost of applying nonpushable other clauses locally
* on the result fetched from the foreign server.
*/
run_cost = fpinfo_i->rel_total_cost - fpinfo_i->rel_startup_cost;
run_cost += fpinfo_o->rel_total_cost - fpinfo_o->rel_startup_cost;
run_cost += nrows * join_cost.per_tuple;
nrows = clamp_row_est(nrows * fpinfo->joinclause_sel);
run_cost += nrows * remote_conds_cost.per_tuple;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
else if (IS_UPPER_REL(foreignrel))
{
RelOptInfo *outerrel = fpinfo->outerrel;
PgFdwRelationInfo *ofpinfo;
AggClauseCosts aggcosts;
double input_rows;
int numGroupCols;
double numGroups = 1;
/* The upper relation should have its outer relation set */
Assert(outerrel);
/* and that outer relation should have its reltarget set */
Assert(outerrel->reltarget);
/*
* This cost model is mixture of costing done for sorted and
* hashed aggregates in cost_agg(). We are not sure which
* strategy will be considered at remote side, thus for
* simplicity, we put all startup related costs in startup_cost
* and all finalization and run cost are added in total_cost.
*/
ofpinfo = (PgFdwRelationInfo *) outerrel->fdw_private;
/* Get rows from input rel */
input_rows = ofpinfo->rows;
/* Collect statistics about aggregates for estimating costs. */
MemSet(&aggcosts, 0, sizeof(AggClauseCosts));
if (root->parse->hasAggs)
{
get_agg_clause_costs(root, (Node *) fpinfo->grouped_tlist,
AGGSPLIT_SIMPLE, &aggcosts);
/*
* The cost of aggregates in the HAVING qual will be the same
* for each child as it is for the parent, so there's no need
* to use a translated version of havingQual.
*/
get_agg_clause_costs(root, (Node *) root->parse->havingQual,
AGGSPLIT_SIMPLE, &aggcosts);
}
/* Get number of grouping columns and possible number of groups */
numGroupCols = list_length(root->parse->groupClause);
numGroups = estimate_num_groups(root,
get_sortgrouplist_exprs(root->parse->groupClause,
fpinfo->grouped_tlist),
input_rows, NULL);
/*
* Get the retrieved_rows and rows estimates. If there are HAVING
* quals, account for their selectivity.
*/
if (root->parse->havingQual)
{
/* Factor in the selectivity of the remotely-checked quals */
retrieved_rows =
clamp_row_est(numGroups *
clauselist_selectivity(root,
fpinfo->remote_conds,
0,
JOIN_INNER,
NULL));
/* Factor in the selectivity of the locally-checked quals */
rows = clamp_row_est(retrieved_rows * fpinfo->local_conds_sel);
}
else
{
rows = retrieved_rows = numGroups;
}
/* Use width estimate made by the core code. */
width = foreignrel->reltarget->width;
/*-----
* Startup cost includes:
* 1. Startup cost for underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Cost of performing aggregation, per cost_agg()
*-----
*/
startup_cost = ofpinfo->rel_startup_cost;
startup_cost += outerrel->reltarget->cost.startup;
startup_cost += aggcosts.transCost.startup;
startup_cost += aggcosts.transCost.per_tuple * input_rows;
startup_cost += aggcosts.finalCost.startup;
startup_cost += (cpu_operator_cost * numGroupCols) * input_rows;
/*-----
* Run time cost includes:
* 1. Run time cost of underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Run time cost of performing aggregation, per cost_agg()
*-----
*/
run_cost = ofpinfo->rel_total_cost - ofpinfo->rel_startup_cost;
run_cost += outerrel->reltarget->cost.per_tuple * input_rows;
run_cost += aggcosts.finalCost.per_tuple * numGroups;
run_cost += cpu_tuple_cost * numGroups;
/* Account for the eval cost of HAVING quals, if any */
if (root->parse->havingQual)
{
QualCost remote_cost;
/* Add in the eval cost of the remotely-checked quals */
cost_qual_eval(&remote_cost, fpinfo->remote_conds, root);
startup_cost += remote_cost.startup;
run_cost += remote_cost.per_tuple * numGroups;
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
}
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
else
{
Cost cpu_per_tuple;
/* Use rows/width estimates made by set_baserel_size_estimates. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most foreignrel->tuples.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, foreignrel->tuples);
/*
* Cost as though this were a seqscan, which is pessimistic. We
* effectively imagine the local_conds are being evaluated
* remotely, too.
*/
startup_cost = 0;
run_cost = 0;
run_cost += seq_page_cost * foreignrel->pages;
startup_cost += foreignrel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + foreignrel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * foreignrel->tuples;
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
/*
* Without remote estimates, we have no real way to estimate the cost
* of generating sorted output. It could be free if the query plan
* the remote side would have chosen generates properly-sorted output
* anyway, but in most cases it will cost something. Estimate a value
* high enough that we won't pick the sorted path when the ordering
* isn't locally useful, but low enough that we'll err on the side of
* pushing down the ORDER BY clause when it's useful to do so.
*/
if (pathkeys != NIL)
{
if (IS_UPPER_REL(foreignrel))
{
Assert(foreignrel->reloptkind == RELOPT_UPPER_REL &&
fpinfo->stage == UPPERREL_GROUP_AGG);
adjust_foreign_grouping_path_cost(root, pathkeys,
retrieved_rows, width,
fpextra->limit_tuples,
&startup_cost, &run_cost);
}
else
{
startup_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
run_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
}
}
total_cost = startup_cost + run_cost;
/* Adjust the cost estimates if we have LIMIT */
if (fpextra && fpextra->has_limit)
{
adjust_limit_rows_costs(&rows, &startup_cost, &total_cost,
fpextra->offset_est, fpextra->count_est);
retrieved_rows = rows;
}
}
/*
* If this includes the final sort step, the given target, which will be
* applied to the resulting path, might have different expressions from
* the foreignrel's reltarget (see make_sort_input_target()); adjust tlist
* eval costs.
*/
if (fpextra && fpextra->has_final_sort &&
fpextra->target != foreignrel->reltarget)
{
QualCost oldcost = foreignrel->reltarget->cost;
QualCost newcost = fpextra->target->cost;
startup_cost += newcost.startup - oldcost.startup;
total_cost += newcost.startup - oldcost.startup;
total_cost += (newcost.per_tuple - oldcost.per_tuple) * rows;
}
/*
* Cache the retrieved rows and cost estimates for scans, joins, or
* groupings without any parameterization, pathkeys, or additional
* post-scan/join-processing steps, before adding the costs for
* transferring data from the foreign server. These estimates are useful
* for costing remote joins involving this relation or costing other
* remote operations on this relation such as remote sorts and remote
* LIMIT restrictions, when the costs can not be obtained from the foreign
* server. This function will be called at least once for every foreign
* relation without any parameterization, pathkeys, or additional
* post-scan/join-processing steps.
*/
if (pathkeys == NIL && param_join_conds == NIL && fpextra == NULL)
{
fpinfo->retrieved_rows = retrieved_rows;
fpinfo->rel_startup_cost = startup_cost;
fpinfo->rel_total_cost = total_cost;
}
/*
* Add some additional cost factors to account for connection overhead
* (fdw_startup_cost), transferring data across the network
* (fdw_tuple_cost per retrieved row), and local manipulation of the data
* (cpu_tuple_cost per retrieved row).
*/
startup_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_tuple_cost * retrieved_rows;
total_cost += cpu_tuple_cost * retrieved_rows;
/*
* If we have LIMIT, we should prefer performing the restriction remotely
* rather than locally, as the former avoids extra row fetches from the
* remote that the latter might cause. But since the core code doesn't
* account for such fetches when estimating the costs of the local
* restriction (see create_limit_path()), there would be no difference
* between the costs of the local restriction and the costs of the remote
* restriction estimated above if we don't use remote estimates (except
* for the case where the foreignrel is a grouping relation, the given
* pathkeys is not NIL, and the effects of a bounded sort for that rel is
* accounted for in costing the remote restriction). Tweak the costs of
* the remote restriction to ensure we'll prefer it if LIMIT is a useful
* one.
*/
if (!fpinfo->use_remote_estimate &&
fpextra && fpextra->has_limit &&
fpextra->limit_tuples > 0 &&
fpextra->limit_tuples < fpinfo->rows)
{
Assert(fpinfo->rows > 0);
total_cost -= (total_cost - startup_cost) * 0.05 *
(fpinfo->rows - fpextra->limit_tuples) / fpinfo->rows;
}
/* Return results. */
*p_rows = rows;
*p_width = width;
*p_startup_cost = startup_cost;
*p_total_cost = total_cost;
}
/*
* Estimate costs of executing a SQL statement remotely.
* The given "sql" must be an EXPLAIN command.
*/
static void
get_remote_estimate(const char *sql, PGconn *conn,
double *rows, int *width,
Cost *startup_cost, Cost *total_cost)
{
PGresult *volatile res = NULL;
/* PGresult must be released before leaving this function. */
PG_TRY();
{
char *line;
char *p;
int n;
/*
* Execute EXPLAIN remotely.
*/
res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql);
/*
* Extract cost numbers for topmost plan node. Note we search for a
* left paren from the end of the line to avoid being confused by
* other uses of parentheses.
*/
line = PQgetvalue(res, 0, 0);
p = strrchr(line, '(');
if (p == NULL)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
n = sscanf(p, "(cost=%lf..%lf rows=%lf width=%d)",
startup_cost, total_cost, rows, width);
if (n != 4)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Adjust the cost estimates of a foreign grouping path to include the cost of
* generating properly-sorted output.
*/
static void
adjust_foreign_grouping_path_cost(PlannerInfo *root,
List *pathkeys,
double retrieved_rows,
double width,
double limit_tuples,
Cost *p_startup_cost,
Cost *p_run_cost)
{
/*
* If the GROUP BY clause isn't sort-able, the plan chosen by the remote
* side is unlikely to generate properly-sorted output, so it would need
* an explicit sort; adjust the given costs with cost_sort(). Likewise,
* if the GROUP BY clause is sort-able but isn't a superset of the given
* pathkeys, adjust the costs with that function. Otherwise, adjust the
* costs by applying the same heuristic as for the scan or join case.
*/
if (!grouping_is_sortable(root->parse->groupClause) ||
!pathkeys_contained_in(pathkeys, root->group_pathkeys))
{
Path sort_path; /* dummy for result of cost_sort */
cost_sort(&sort_path,
root,
pathkeys,
*p_startup_cost + *p_run_cost,
retrieved_rows,
width,
0.0,
work_mem,
limit_tuples);
*p_startup_cost = sort_path.startup_cost;
*p_run_cost = sort_path.total_cost - sort_path.startup_cost;
}
else
{
/*
* The default extra cost seems too large for foreign-grouping cases;
* add 1/4th of that default.
*/
double sort_multiplier = 1.0 + (DEFAULT_FDW_SORT_MULTIPLIER
- 1.0) * 0.25;
*p_startup_cost *= sort_multiplier;
*p_run_cost *= sort_multiplier;
}
}
/*
* Detect whether we want to process an EquivalenceClass member.
*
* This is a callback for use by generate_implied_equalities_for_column.
*/
static bool
ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg)
{
ec_member_foreign_arg *state = (ec_member_foreign_arg *) arg;
Expr *expr = em->em_expr;
/*
* If we've identified what we're processing in the current scan, we only
* want to match that expression.
*/
if (state->current != NULL)
return equal(expr, state->current);
/*
* Otherwise, ignore anything we've already processed.
*/
if (list_member(state->already_used, expr))
return false;
/* This is the new target to process. */
state->current = expr;
return true;
}
/*
* Create cursor for node's query with current parameter values.
*/
static void
create_cursor(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = fsstate->numParams;
const char **values = fsstate->param_values;
PGconn *conn = fsstate->conn;
StringInfoData buf;
PGresult *res;
/*
* Construct array of query parameter values in text format. We do the
* conversions in the short-lived per-tuple context, so as not to cause a
* memory leak over repeated scans.
*/
if (numParams > 0)
{
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
process_query_params(econtext,
fsstate->param_flinfo,
fsstate->param_exprs,
values);
MemoryContextSwitchTo(oldcontext);
}
/* Construct the DECLARE CURSOR command */
initStringInfo(&buf);
appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s",
fsstate->cursor_number, fsstate->query);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*/
if (!PQsendQueryParams(conn, buf.data, numParams,
NULL, values, NULL, NULL, 0))
pgfdw_report_error(ERROR, NULL, conn, false, buf.data);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(conn, buf.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, fsstate->query);
PQclear(res);
/* Mark the cursor as created, and show no tuples have been retrieved */
fsstate->cursor_exists = true;
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
/* Clean up */
pfree(buf.data);
}
/*
* Fetch some more rows from the node's cursor.
*/
static void
fetch_more_data(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
PGresult *volatile res = NULL;
MemoryContext oldcontext;
/*
* We'll store the tuples in the batch_cxt. First, flush the previous
* batch.
*/
fsstate->tuples = NULL;
MemoryContextReset(fsstate->batch_cxt);
oldcontext = MemoryContextSwitchTo(fsstate->batch_cxt);
/* PGresult must be released before leaving this function. */
PG_TRY();
{
PGconn *conn = fsstate->conn;
char sql[64];
int numrows;
int i;
snprintf(sql, sizeof(sql), "FETCH %d FROM c%u",
fsstate->fetch_size, fsstate->cursor_number);
res = pgfdw_exec_query(conn, sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, fsstate->query);
/* Convert the data into HeapTuples */
numrows = PQntuples(res);
fsstate->tuples = (HeapTuple *) palloc0(numrows * sizeof(HeapTuple));
fsstate->num_tuples = numrows;
fsstate->next_tuple = 0;
for (i = 0; i < numrows; i++)
{
Assert(IsA(node->ss.ps.plan, ForeignScan));
fsstate->tuples[i] =
make_tuple_from_result_row(res, i,
fsstate->rel,
fsstate->attinmeta,
fsstate->retrieved_attrs,
node,
fsstate->temp_cxt);
}
/* Update fetch_ct_2 */
if (fsstate->fetch_ct_2 < 2)
fsstate->fetch_ct_2++;
/* Must be EOF if we didn't get as many tuples as we asked for. */
fsstate->eof_reached = (numrows < fsstate->fetch_size);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcontext);
}
/*
* Force assorted GUC parameters to settings that ensure that we'll output
* data values in a form that is unambiguous to the remote server.
*
* This is rather expensive and annoying to do once per row, but there's
* little choice if we want to be sure values are transmitted accurately;
* we can't leave the settings in place between rows for fear of affecting
* user-visible computations.
*
* We use the equivalent of a function SET option to allow the settings to
* persist only until the caller calls reset_transmission_modes(). If an
* error is thrown in between, guc.c will take care of undoing the settings.
*
* The return value is the nestlevel that must be passed to
* reset_transmission_modes() to undo things.
*/
int
set_transmission_modes(void)
{
int nestlevel = NewGUCNestLevel();
/*
* The values set here should match what pg_dump does. See also
* configure_remote_session in connection.c.
*/
if (DateStyle != USE_ISO_DATES)
(void) set_config_option("datestyle", "ISO",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
if (IntervalStyle != INTSTYLE_POSTGRES)
(void) set_config_option("intervalstyle", "postgres",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
if (extra_float_digits < 3)
(void) set_config_option("extra_float_digits", "3",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
return nestlevel;
}
/*
* Undo the effects of set_transmission_modes().
*/
void
reset_transmission_modes(int nestlevel)
{
AtEOXact_GUC(true, nestlevel);
}
/*
* Utility routine to close a cursor.
*/
static void
close_cursor(PGconn *conn, unsigned int cursor_number)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "CLOSE c%u", cursor_number);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, sql);
PQclear(res);
}
/*
* create_foreign_modify
* Construct an execution state of a foreign insert/update/delete
* operation
*/
static PgFdwModifyState *
create_foreign_modify(EState *estate,
RangeTblEntry *rte,
ResultRelInfo *resultRelInfo,
CmdType operation,
Plan *subplan,
char *query,
List *target_attrs,
bool has_returning,
List *retrieved_attrs)
{
PgFdwModifyState *fmstate;
Relation rel = resultRelInfo->ri_RelationDesc;
TupleDesc tupdesc = RelationGetDescr(rel);
Oid userid;
ForeignTable *table;
UserMapping *user;
AttrNumber n_params;
Oid typefnoid;
bool isvarlena;
ListCell *lc;
/* Begin constructing PgFdwModifyState. */
fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
fmstate->rel = rel;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(RelationGetRelid(rel));
user = GetUserMapping(userid, table->serverid);
/* Open connection; report that we'll create a prepared statement. */
fmstate->conn = GetConnection(user, true);
fmstate->p_name = NULL; /* prepared statement not made yet */
/* Set up remote query information. */
fmstate->query = query;
fmstate->target_attrs = target_attrs;
fmstate->has_returning = has_returning;
fmstate->retrieved_attrs = retrieved_attrs;
/* Create context for per-tuple temp workspace. */
fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/* Prepare for input conversion of RETURNING results. */
if (fmstate->has_returning)
fmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
/* Prepare for output conversion of parameters used in prepared stmt. */
n_params = list_length(fmstate->target_attrs) + 1;
fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
fmstate->p_nums = 0;
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
Assert(subplan != NULL);
/* Find the ctid resjunk column in the subplan's result */
fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
"ctid");
if (!AttributeNumberIsValid(fmstate->ctidAttno))
elog(ERROR, "could not find junk ctid column");
/* First transmittable parameter will be ctid */
getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
if (operation == CMD_INSERT || operation == CMD_UPDATE)
{
/* Set up for remaining transmittable parameters */
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
Assert(!attr->attisdropped);
getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
}
Assert(fmstate->p_nums <= n_params);
/* Initialize auxiliary state */
fmstate->aux_fmstate = NULL;
return fmstate;
}
/*
* execute_foreign_modify
* Perform foreign-table modification as required, and fetch RETURNING
* result if any. (This is the shared guts of postgresExecForeignInsert,
* postgresExecForeignUpdate, and postgresExecForeignDelete.)
*/
static TupleTableSlot *
execute_foreign_modify(EState *estate,
ResultRelInfo *resultRelInfo,
CmdType operation,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
ItemPointer ctid = NULL;
const char **p_values;
PGresult *res;
int n_rows;
/* The operation should be INSERT, UPDATE, or DELETE */
Assert(operation == CMD_INSERT ||
operation == CMD_UPDATE ||
operation == CMD_DELETE);
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/*
* For UPDATE/DELETE, get the ctid that was passed up as a resjunk column
*/
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
Datum datum;
bool isNull;
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
ctid = (ItemPointer) DatumGetPointer(datum);
}
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate, ctid, slot);
/*
* Execute the prepared statement.
*/
if (!PQsendQueryPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0))
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/*
* Return NULL if nothing was inserted/updated/deleted on the remote end
*/
return (n_rows > 0) ? slot : NULL;
}
/*
* prepare_foreign_modify
* Establish a prepared statement for execution of INSERT/UPDATE/DELETE
*/
static void
prepare_foreign_modify(PgFdwModifyState *fmstate)
{
char prep_name[NAMEDATALEN];
char *p_name;
PGresult *res;
/* Construct name we'll use for the prepared statement. */
snprintf(prep_name, sizeof(prep_name), "pgsql_fdw_prep_%u",
GetPrepStmtNumber(fmstate->conn));
p_name = pstrdup(prep_name);
/*
* We intentionally do not specify parameter types here, but leave the
* remote server to derive them by default. This avoids possible problems
* with the remote server using different type OIDs than we do. All of
* the prepared statements we use in this module are simple enough that
* the remote server will make the right choices.
*/
if (!PQsendPrepare(fmstate->conn,
p_name,
fmstate->query,
0,
NULL))
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
PQclear(res);
/* This action shows that the prepare has been done. */
fmstate->p_name = p_name;
}
/*
* convert_prep_stmt_params
* Create array of text strings representing parameter values
*
* tupleid is ctid to send, or NULL if none
* slot is slot to get remaining parameters from, or NULL if none
*
* Data is constructed in temp_cxt; caller should reset that after use.
*/
static const char **
convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot)
{
const char **p_values;
int pindex = 0;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(fmstate->temp_cxt);
p_values = (const char **) palloc(sizeof(char *) * fmstate->p_nums);
/* 1st parameter should be ctid, if it's in use */
if (tupleid != NULL)
{
/* don't need set_transmission_modes for TID output */
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
PointerGetDatum(tupleid));
pindex++;
}
/* get following parameters from slot */
if (slot != NULL && fmstate->target_attrs != NIL)
{
int nestlevel;
ListCell *lc;
nestlevel = set_transmission_modes();
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Datum value;
bool isnull;
value = slot_getattr(slot, attnum, &isnull);
if (isnull)
p_values[pindex] = NULL;
else
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
value);
pindex++;
}
reset_transmission_modes(nestlevel);
}
Assert(pindex == fmstate->p_nums);
MemoryContextSwitchTo(oldcontext);
return p_values;
}
/*
* store_returning_result
* Store the result of a RETURNING clause
*
* On error, be sure to release the PGresult on the way out. Callers do not
* have PG_TRY blocks to ensure this happens.
*/
static void
store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res)
{
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(res, 0,
fmstate->rel,
fmstate->attinmeta,
fmstate->retrieved_attrs,
NULL,
fmstate->temp_cxt);
/*
* The returning slot will not necessarily be suitable to store
* heaptuples directly, so allow for conversion.
*/
ExecForceStoreHeapTuple(newtup, slot, true);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* finish_foreign_modify
* Release resources for a foreign insert/update/delete operation
*/
static void
finish_foreign_modify(PgFdwModifyState *fmstate)
{
Assert(fmstate != NULL);
/* If we created a prepared statement, destroy it */
if (fmstate->p_name)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(fmstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
PQclear(res);
fmstate->p_name = NULL;
}
/* Release remote connection */
ReleaseConnection(fmstate->conn);
fmstate->conn = NULL;
}
/*
* build_remote_returning
* Build a RETURNING targetlist of a remote query for performing an
* UPDATE/DELETE .. RETURNING on a join directly
*/
static List *
build_remote_returning(Index rtindex, Relation rel, List *returningList)
{
bool have_wholerow = false;
List *tlist = NIL;
List *vars;
ListCell *lc;
Assert(returningList);
vars = pull_var_clause((Node *) returningList, PVC_INCLUDE_PLACEHOLDERS);
/*
* If there's a whole-row reference to the target relation, then we'll
* need all the columns of the relation.
*/
foreach(lc, vars)
{
Var *var = (Var *) lfirst(lc);
if (IsA(var, Var) &&
var->varno == rtindex &&
var->varattno == InvalidAttrNumber)
{
have_wholerow = true;
break;
}
}
if (have_wholerow)
{
TupleDesc tupdesc = RelationGetDescr(rel);
int i;
for (i = 1; i <= tupdesc->natts; i++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, i - 1);
Var *var;
/* Ignore dropped attributes. */
if (attr->attisdropped)
continue;
var = makeVar(rtindex,
i,
attr->atttypid,
attr->atttypmod,
attr->attcollation,
0);
tlist = lappend(tlist,
makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
NULL,
false));
}
}
/* Now add any remaining columns to tlist. */
foreach(lc, vars)
{
Var *var = (Var *) lfirst(lc);
/*
* No need for whole-row references to the target relation. We don't
* need system columns other than ctid and oid either, since those are
* set locally.
*/
if (IsA(var, Var) &&
var->varno == rtindex &&
var->varattno <= InvalidAttrNumber &&
var->varattno != SelfItemPointerAttributeNumber)
continue; /* don't need it */
if (tlist_member((Expr *) var, tlist))
continue; /* already got it */
tlist = lappend(tlist,
makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
NULL,
false));
}
list_free(vars);
return tlist;
}
/*
* rebuild_fdw_scan_tlist
* Build new fdw_scan_tlist of given foreign-scan plan node from given
* tlist
*
* There might be columns that the fdw_scan_tlist of the given foreign-scan
* plan node contains that the given tlist doesn't. The fdw_scan_tlist would
* have contained resjunk columns such as 'ctid' of the target relation and
* 'wholerow' of non-target relations, but the tlist might not contain them,
* for example. So, adjust the tlist so it contains all the columns specified
* in the fdw_scan_tlist; else setrefs.c will get confused.
*/
static void
rebuild_fdw_scan_tlist(ForeignScan *fscan, List *tlist)
{
List *new_tlist = tlist;
List *old_tlist = fscan->fdw_scan_tlist;
ListCell *lc;
foreach(lc, old_tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
if (tlist_member(tle->expr, new_tlist))
continue; /* already got it */
new_tlist = lappend(new_tlist,
makeTargetEntry(tle->expr,
list_length(new_tlist) + 1,
NULL,
false));
}
fscan->fdw_scan_tlist = new_tlist;
}
/*
* Execute a direct UPDATE/DELETE statement.
*/
static void
execute_dml_stmt(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = dmstate->numParams;
const char **values = dmstate->param_values;
/*
* Construct array of query parameter values in text format.
*/
if (numParams > 0)
process_query_params(econtext,
dmstate->param_flinfo,
dmstate->param_exprs,
values);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*/
if (!PQsendQueryParams(dmstate->conn, dmstate->query, numParams,
NULL, values, NULL, NULL, 0))
pgfdw_report_error(ERROR, NULL, dmstate->conn, false, dmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
dmstate->result = pgfdw_get_result(dmstate->conn, dmstate->query);
if (PQresultStatus(dmstate->result) !=
(dmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, dmstate->result, dmstate->conn, true,
dmstate->query);
/* Get the number of rows affected. */
if (dmstate->has_returning)
dmstate->num_tuples = PQntuples(dmstate->result);
else
dmstate->num_tuples = atoi(PQcmdTuples(dmstate->result));
}
/*
* Get the result of a RETURNING clause.
*/
static TupleTableSlot *
get_returning_data(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
EState *estate = node->ss.ps.state;
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
TupleTableSlot *resultSlot;
Assert(resultRelInfo->ri_projectReturning);
/* If we didn't get any tuples, must be end of data. */
if (dmstate->next_tuple >= dmstate->num_tuples)
return ExecClearTuple(slot);
/* Increment the command es_processed count if necessary. */
if (dmstate->set_processed)
estate->es_processed += 1;
/*
* Store a RETURNING tuple. If has_returning is false, just emit a dummy
* tuple. (has_returning is false when the local query is of the form
* "UPDATE/DELETE .. RETURNING 1" for example.)
*/
if (!dmstate->has_returning)
{
ExecStoreAllNullTuple(slot);
resultSlot = slot;
}
else
{
/*
* On error, be sure to release the PGresult on the way out. Callers
* do not have PG_TRY blocks to ensure this happens.
*/
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(dmstate->result,
dmstate->next_tuple,
dmstate->rel,
dmstate->attinmeta,
dmstate->retrieved_attrs,
node,
dmstate->temp_cxt);
ExecStoreHeapTuple(newtup, slot, false);
}
PG_CATCH();
{
if (dmstate->result)
PQclear(dmstate->result);
PG_RE_THROW();
}
PG_END_TRY();
/* Get the updated/deleted tuple. */
if (dmstate->rel)
resultSlot = slot;
else
resultSlot = apply_returning_filter(dmstate, slot, estate);
}
dmstate->next_tuple++;
/* Make slot available for evaluation of the local query RETURNING list. */
resultRelInfo->ri_projectReturning->pi_exprContext->ecxt_scantuple =
resultSlot;
return slot;
}
/*
* Initialize a filter to extract an updated/deleted tuple from a scan tuple.
*/
static void
init_returning_filter(PgFdwDirectModifyState *dmstate,
List *fdw_scan_tlist,
Index rtindex)
{
TupleDesc resultTupType = RelationGetDescr(dmstate->resultRel);
ListCell *lc;
int i;
/*
* Calculate the mapping between the fdw_scan_tlist's entries and the
* result tuple's attributes.
*
* The "map" is an array of indexes of the result tuple's attributes in
* fdw_scan_tlist, i.e., one entry for every attribute of the result
* tuple. We store zero for any attributes that don't have the
* corresponding entries in that list, marking that a NULL is needed in
* the result tuple.
*
* Also get the indexes of the entries for ctid and oid if any.
*/
dmstate->attnoMap = (AttrNumber *)
palloc0(resultTupType->natts * sizeof(AttrNumber));
dmstate->ctidAttno = dmstate->oidAttno = 0;
i = 1;
dmstate->hasSystemCols = false;
foreach(lc, fdw_scan_tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
Var *var = (Var *) tle->expr;
Assert(IsA(var, Var));
/*
* If the Var is a column of the target relation to be retrieved from
* the foreign server, get the index of the entry.
*/
if (var->varno == rtindex &&
list_member_int(dmstate->retrieved_attrs, i))
{
int attrno = var->varattno;
if (attrno < 0)
{
/*
* We don't retrieve system columns other than ctid and oid.
*/
if (attrno == SelfItemPointerAttributeNumber)
dmstate->ctidAttno = i;
else
Assert(false);
dmstate->hasSystemCols = true;
}
else
{
/*
* We don't retrieve whole-row references to the target
* relation either.
*/
Assert(attrno > 0);
dmstate->attnoMap[attrno - 1] = i;
}
}
i++;
}
}
/*
* Extract and return an updated/deleted tuple from a scan tuple.
*/
static TupleTableSlot *
apply_returning_filter(PgFdwDirectModifyState *dmstate,
TupleTableSlot *slot,
EState *estate)
{
ResultRelInfo *relInfo = estate->es_result_relation_info;
TupleDesc resultTupType = RelationGetDescr(dmstate->resultRel);
TupleTableSlot *resultSlot;
Datum *values;
bool *isnull;
Datum *old_values;
bool *old_isnull;
int i;
/*
* Use the return tuple slot as a place to store the result tuple.
*/
resultSlot = ExecGetReturningSlot(estate, relInfo);
/*
* Extract all the values of the scan tuple.
*/
slot_getallattrs(slot);
old_values = slot->tts_values;
old_isnull = slot->tts_isnull;
/*
* Prepare to build the result tuple.
*/
ExecClearTuple(resultSlot);
values = resultSlot->tts_values;
isnull = resultSlot->tts_isnull;
/*
* Transpose data into proper fields of the result tuple.
*/
for (i = 0; i < resultTupType->natts; i++)
{
int j = dmstate->attnoMap[i];
if (j == 0)
{
values[i] = (Datum) 0;
isnull[i] = true;
}
else
{
values[i] = old_values[j - 1];
isnull[i] = old_isnull[j - 1];
}
}
/*
* Build the virtual tuple.
*/
ExecStoreVirtualTuple(resultSlot);
/*
* If we have any system columns to return, materialize a heap tuple in
* the slot from column values set above and install system columns in
* that tuple.
*/
if (dmstate->hasSystemCols)
{
HeapTuple resultTup = ExecFetchSlotHeapTuple(resultSlot, true, NULL);
/* ctid */
if (dmstate->ctidAttno)
{
ItemPointer ctid = NULL;
ctid = (ItemPointer) DatumGetPointer(old_values[dmstate->ctidAttno - 1]);
resultTup->t_self = *ctid;
}
/*
* And remaining columns
*
* Note: since we currently don't allow the target relation to appear
* on the nullable side of an outer join, any system columns wouldn't
* go to NULL.
*
* Note: no need to care about tableoid here because it will be
* initialized in ExecProcessReturning().
*/
HeapTupleHeaderSetXmin(resultTup->t_data, InvalidTransactionId);
HeapTupleHeaderSetXmax(resultTup->t_data, InvalidTransactionId);
HeapTupleHeaderSetCmin(resultTup->t_data, InvalidTransactionId);
}
/*
* And return the result tuple.
*/
return resultSlot;
}
/*
* Prepare for processing of parameters used in remote query.
*/
static void
prepare_query_params(PlanState *node,
List *fdw_exprs,
int numParams,
FmgrInfo **param_flinfo,
List **param_exprs,
const char ***param_values)
{
int i;
ListCell *lc;
Assert(numParams > 0);
/* Prepare for output conversion of parameters used in remote query. */
*param_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * numParams);
i = 0;
foreach(lc, fdw_exprs)
{
Node *param_expr = (Node *) lfirst(lc);
Oid typefnoid;
bool isvarlena;
getTypeOutputInfo(exprType(param_expr), &typefnoid, &isvarlena);
fmgr_info(typefnoid, &(*param_flinfo)[i]);
i++;
}
/*
* Prepare remote-parameter expressions for evaluation. (Note: in
* practice, we expect that all these expressions will be just Params, so
* we could possibly do something more efficient than using the full
* expression-eval machinery for this. But probably there would be little
* benefit, and it'd require postgres_fdw to know more than is desirable
* about Param evaluation.)
*/
*param_exprs = ExecInitExprList(fdw_exprs, node);
/* Allocate buffer for text form of query parameters. */
*param_values = (const char **) palloc0(numParams * sizeof(char *));
}
/*
* Construct array of query parameter values in text format.
*/
static void
process_query_params(ExprContext *econtext,
FmgrInfo *param_flinfo,
List *param_exprs,
const char **param_values)
{
int nestlevel;
int i;
ListCell *lc;
nestlevel = set_transmission_modes();
i = 0;
foreach(lc, param_exprs)
{
ExprState *expr_state = (ExprState *) lfirst(lc);
Datum expr_value;
bool isNull;
/* Evaluate the parameter expression */
expr_value = ExecEvalExpr(expr_state, econtext, &isNull);
/*
* Get string representation of each parameter value by invoking
* type-specific output function, unless the value is null.
*/
if (isNull)
param_values[i] = NULL;
else
param_values[i] = OutputFunctionCall(&param_flinfo[i], expr_value);
i++;
}
reset_transmission_modes(nestlevel);
}
/*
* postgresAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool
postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages)
{
ForeignTable *table;
UserMapping *user;
PGconn *conn;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Return the row-analysis function pointer */
*func = postgresAcquireSampleRowsFunc;
/*
* Now we have to get the number of pages. It's annoying that the ANALYZE
* API requires us to return that now, because it forces some duplication
* of effort between this routine and postgresAcquireSampleRowsFunc. But
* it's probably not worth redefining that API at this point.
*/
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
user = GetUserMapping(relation->rd_rel->relowner, table->serverid);
conn = GetConnection(user, false);
/*
* Construct command to get page count for relation.
*/
initStringInfo(&sql);
deparseAnalyzeSizeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
if (PQntuples(res) != 1 || PQnfields(res) != 1)
elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query");
*totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return true;
}
/*
* Acquire a random sample of rows from foreign table managed by postgres_fdw.
*
* We fetch the whole table from the remote side and pick out some sample rows.
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the table and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the table. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int
postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows)
{
PgFdwAnalyzeState astate;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
unsigned int cursor_number;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Initialize workspace state */
astate.rel = relation;
astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation));
astate.rows = rows;
astate.targrows = targrows;
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
reservoir_init_selection_state(&astate.rstate, targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, table->serverid);
conn = GetConnection(user, false);
/*
* Construct cursor that retrieves whole rows from remote.
*/
cursor_number = GetCursorNumber(conn);
initStringInfo(&sql);
appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number);
deparseAnalyzeSql(&sql, relation, &astate.retrieved_attrs);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
char fetch_sql[64];
int fetch_size;
ListCell *lc;
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
PQclear(res);
res = NULL;
/*
* Determine the fetch size. The default is arbitrary, but shouldn't
* be enormous.
*/
fetch_size = 100;
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "fetch_size") == 0)
{
fetch_size = strtol(defGetString(def), NULL, 10);
break;
}
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "fetch_size") == 0)
{
fetch_size = strtol(defGetString(def), NULL, 10);
break;
}
}
/* Construct command to fetch rows from remote. */
snprintf(fetch_sql, sizeof(fetch_sql), "FETCH %d FROM c%u",
fetch_size, cursor_number);
/* Retrieve and process rows a batch at a time. */
for (;;)
{
int numrows;
int i;
/* Allow users to cancel long query */
CHECK_FOR_INTERRUPTS();
/*
* XXX possible future improvement: if rowstoskip is large, we
* could issue a MOVE rather than physically fetching the rows,
* then just adjust rowstoskip and samplerows appropriately.
*/
/* Fetch some rows */
res = pgfdw_exec_query(conn, fetch_sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
/* Process whatever we got. */
numrows = PQntuples(res);
for (i = 0; i < numrows; i++)
analyze_row_processor(res, i, &astate);
PQclear(res);
res = NULL;
/* Must be EOF if we didn't get all the rows requested. */
if (numrows < fetch_size)
break;
}
/* Close the cursor, just to be tidy. */
close_cursor(conn, cursor_number);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
/* We assume that we have no dead tuple. */
*totaldeadrows = 0.0;
/* We've retrieved all living tuples from foreign server. */
*totalrows = astate.samplerows;
/*
* Emit some interesting relation info
*/
ereport(elevel,
(errmsg("\"%s\": table contains %.0f rows, %d rows in sample",
RelationGetRelationName(relation),
astate.samplerows, astate.numrows)));
return astate.numrows;
}
/*
* Collect sample rows from the result of query.
* - Use all tuples in sample until target # of samples are collected.
* - Subsequently, replace already-sampled tuples randomly.
*/
static void
analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
{
int targrows = astate->targrows;
int pos; /* array index to store tuple in */
MemoryContext oldcontext;
/* Always increment sample row counter. */
astate->samplerows += 1;
/*
* Determine the slot where this sample row should be stored. Set pos to
* negative value to indicate the row should be skipped.
*/
if (astate->numrows < targrows)
{
/* First targrows rows are always included into the sample */
pos = astate->numrows++;
}
else
{
/*
* Now we start replacing tuples in the sample until we reach the end
* of the relation. Same algorithm as in acquire_sample_rows in
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0)
astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
if (astate->rowstoskip <= 0)
{
/* Choose a random reservoir element to replace. */
pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
}
else
{
/* Skip this tuple. */
pos = -1;
}
astate->rowstoskip -= 1;
}
if (pos >= 0)
{
/*
* Create sample tuple from current result row, and store it in the
* position determined above. The tuple has to be created in anl_cxt.
*/
oldcontext = MemoryContextSwitchTo(astate->anl_cxt);
astate->rows[pos] = make_tuple_from_result_row(res, row,
astate->rel,
astate->attinmeta,
astate->retrieved_attrs,
NULL,
astate->temp_cxt);
MemoryContextSwitchTo(oldcontext);
}
}
/*
* Import a foreign schema
*/
static List *
postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid)
{
List *commands = NIL;
bool import_collate = true;
bool import_default = false;
bool import_not_null = true;
ForeignServer *server;
UserMapping *mapping;
PGconn *conn;
StringInfoData buf;
PGresult *volatile res = NULL;
int numrows,
i;
ListCell *lc;
/* Parse statement options */
foreach(lc, stmt->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "import_collate") == 0)
import_collate = defGetBoolean(def);
else if (strcmp(def->defname, "import_default") == 0)
import_default = defGetBoolean(def);
else if (strcmp(def->defname, "import_not_null") == 0)
import_not_null = defGetBoolean(def);
else
ereport(ERROR,
(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
errmsg("invalid option \"%s\"", def->defname)));
}
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
server = GetForeignServer(serverOid);
mapping = GetUserMapping(GetUserId(), server->serverid);
conn = GetConnection(mapping, false);
/* Don't attempt to import collation if remote server hasn't got it */
if (PQserverVersion(conn) < 90100)
import_collate = false;
/* Create workspace for strings */
initStringInfo(&buf);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
/* Check that the schema really exists */
appendStringInfoString(&buf, "SELECT 1 FROM pg_catalog.pg_namespace WHERE nspname = ");
deparseStringLiteral(&buf, stmt->remote_schema);
res = pgfdw_exec_query(conn, buf.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, buf.data);
if (PQntuples(res) != 1)
ereport(ERROR,
(errcode(ERRCODE_FDW_SCHEMA_NOT_FOUND),
errmsg("schema \"%s\" is not present on foreign server \"%s\"",
stmt->remote_schema, server->servername)));
PQclear(res);
res = NULL;
resetStringInfo(&buf);
/*
* Fetch all table data from this schema, possibly restricted by
* EXCEPT or LIMIT TO. (We don't actually need to pay any attention
* to EXCEPT/LIMIT TO here, because the core code will filter the
* statements we return according to those lists anyway. But it
* should save a few cycles to not process excluded tables in the
* first place.)
*
* Ignore table data for partitions and only include the definitions
* of the root partitioned tables to allow access to the complete
* remote data set locally in the schema imported.
*
* Note: because we run the connection with search_path restricted to
* pg_catalog, the format_type() and pg_get_expr() outputs will always
* include a schema name for types/functions in other schemas, which
* is what we want.
*/
if (import_collate)
appendStringInfoString(&buf,
"SELECT relname, "
" attname, "
" format_type(atttypid, atttypmod), "
" attnotnull, "
" pg_get_expr(adbin, adrelid), "
" collname, "
" collnsp.nspname "
"FROM pg_class c "
" JOIN pg_namespace n ON "
" relnamespace = n.oid "
" LEFT JOIN pg_attribute a ON "
" attrelid = c.oid AND attnum > 0 "
" AND NOT attisdropped "
" LEFT JOIN pg_attrdef ad ON "
" adrelid = c.oid AND adnum = attnum "
" LEFT JOIN pg_collation coll ON "
" coll.oid = attcollation "
" LEFT JOIN pg_namespace collnsp ON "
" collnsp.oid = collnamespace ");
else
appendStringInfoString(&buf,
"SELECT relname, "
" attname, "
" format_type(atttypid, atttypmod), "
" attnotnull, "
" pg_get_expr(adbin, adrelid), "
" NULL, NULL "
"FROM pg_class c "
" JOIN pg_namespace n ON "
" relnamespace = n.oid "
" LEFT JOIN pg_attribute a ON "
" attrelid = c.oid AND attnum > 0 "
" AND NOT attisdropped "
" LEFT JOIN pg_attrdef ad ON "
" adrelid = c.oid AND adnum = attnum ");
appendStringInfoString(&buf,
"WHERE c.relkind IN ("
CppAsString2(RELKIND_RELATION) ","
CppAsString2(RELKIND_VIEW) ","
CppAsString2(RELKIND_FOREIGN_TABLE) ","
CppAsString2(RELKIND_MATVIEW) ","
CppAsString2(RELKIND_PARTITIONED_TABLE) ") "
" AND n.nspname = ");
deparseStringLiteral(&buf, stmt->remote_schema);
/* Partitions are supported since Postgres 10 */
if (PQserverVersion(conn) >= 100000)
appendStringInfoString(&buf, " AND NOT c.relispartition ");
/* Apply restrictions for LIMIT TO and EXCEPT */
if (stmt->list_type == FDW_IMPORT_SCHEMA_LIMIT_TO ||
stmt->list_type == FDW_IMPORT_SCHEMA_EXCEPT)
{
bool first_item = true;
appendStringInfoString(&buf, " AND c.relname ");
if (stmt->list_type == FDW_IMPORT_SCHEMA_EXCEPT)
appendStringInfoString(&buf, "NOT ");
appendStringInfoString(&buf, "IN (");
/* Append list of table names within IN clause */
foreach(lc, stmt->table_list)
{
RangeVar *rv = (RangeVar *) lfirst(lc);
if (first_item)
first_item = false;
else
appendStringInfoString(&buf, ", ");
deparseStringLiteral(&buf, rv->relname);
}
appendStringInfoChar(&buf, ')');
}
/* Append ORDER BY at the end of query to ensure output ordering */
appendStringInfoString(&buf, " ORDER BY c.relname, a.attnum");
/* Fetch the data */
res = pgfdw_exec_query(conn, buf.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, buf.data);
/* Process results */
numrows = PQntuples(res);
/* note: incrementation of i happens in inner loop's while() test */
for (i = 0; i < numrows;)
{
char *tablename = PQgetvalue(res, i, 0);
bool first_item = true;
resetStringInfo(&buf);
appendStringInfo(&buf, "CREATE FOREIGN TABLE %s (\n",
quote_identifier(tablename));
/* Scan all rows for this table */
do
{
char *attname;
char *typename;
char *attnotnull;
char *attdefault;
char *collname;
char *collnamespace;
/* If table has no columns, we'll see nulls here */
if (PQgetisnull(res, i, 1))
continue;
attname = PQgetvalue(res, i, 1);
typename = PQgetvalue(res, i, 2);
attnotnull = PQgetvalue(res, i, 3);
attdefault = PQgetisnull(res, i, 4) ? (char *) NULL :
PQgetvalue(res, i, 4);
collname = PQgetisnull(res, i, 5) ? (char *) NULL :
PQgetvalue(res, i, 5);
collnamespace = PQgetisnull(res, i, 6) ? (char *) NULL :
PQgetvalue(res, i, 6);
if (first_item)
first_item = false;
else
appendStringInfoString(&buf, ",\n");
/* Print column name and type */
appendStringInfo(&buf, " %s %s",
quote_identifier(attname),
typename);
/*
* Add column_name option so that renaming the foreign table's
* column doesn't break the association to the underlying
* column.
*/
appendStringInfoString(&buf, " OPTIONS (column_name ");
deparseStringLiteral(&buf, attname);
appendStringInfoChar(&buf, ')');
/* Add COLLATE if needed */
if (import_collate && collname != NULL && collnamespace != NULL)
appendStringInfo(&buf, " COLLATE %s.%s",
quote_identifier(collnamespace),
quote_identifier(collname));
/* Add DEFAULT if needed */
if (import_default && attdefault != NULL)
appendStringInfo(&buf, " DEFAULT %s", attdefault);
/* Add NOT NULL if needed */
if (import_not_null && attnotnull[0] == 't')
appendStringInfoString(&buf, " NOT NULL");
}
while (++i < numrows &&
strcmp(PQgetvalue(res, i, 0), tablename) == 0);
/*
* Add server name and table-level options. We specify remote
* schema and table name as options (the latter to ensure that
* renaming the foreign table doesn't break the association).
*/
appendStringInfo(&buf, "\n) SERVER %s\nOPTIONS (",
quote_identifier(server->servername));
appendStringInfoString(&buf, "schema_name ");
deparseStringLiteral(&buf, stmt->remote_schema);
appendStringInfoString(&buf, ", table_name ");
deparseStringLiteral(&buf, tablename);
appendStringInfoString(&buf, ");");
commands = lappend(commands, pstrdup(buf.data));
}
/* Clean up */
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return commands;
}
/*
* Assess whether the join between inner and outer relations can be pushed down
* to the foreign server. As a side effect, save information we obtain in this
* function to PgFdwRelationInfo passed in.
*/
static bool
foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
RelOptInfo *outerrel, RelOptInfo *innerrel,
JoinPathExtraData *extra)
{
PgFdwRelationInfo *fpinfo;
PgFdwRelationInfo *fpinfo_o;
PgFdwRelationInfo *fpinfo_i;
ListCell *lc;
List *joinclauses;
/*
* We support pushing down INNER, LEFT, RIGHT and FULL OUTER joins.
* Constructing queries representing SEMI and ANTI joins is hard, hence
* not considered right now.
*/
if (jointype != JOIN_INNER && jointype != JOIN_LEFT &&
jointype != JOIN_RIGHT && jointype != JOIN_FULL)
return false;
/*
* If either of the joining relations is marked as unsafe to pushdown, the
* join can not be pushed down.
*/
fpinfo = (PgFdwRelationInfo *) joinrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *) outerrel->fdw_private;
fpinfo_i = (PgFdwRelationInfo *) innerrel->fdw_private;
if (!fpinfo_o || !fpinfo_o->pushdown_safe ||
!fpinfo_i || !fpinfo_i->pushdown_safe)
return false;
/*
* If joining relations have local conditions, those conditions are
* required to be applied before joining the relations. Hence the join can
* not be pushed down.
*/
if (fpinfo_o->local_conds || fpinfo_i->local_conds)
return false;
/*
* Merge FDW options. We might be tempted to do this after we have deemed
* the foreign join to be OK. But we must do this beforehand so that we
* know which quals can be evaluated on the foreign server, which might
* depend on shippable_extensions.
*/
fpinfo->server = fpinfo_o->server;
merge_fdw_options(fpinfo, fpinfo_o, fpinfo_i);
/*
* Separate restrict list into join quals and pushed-down (other) quals.
*
* Join quals belonging to an outer join must all be shippable, else we
* cannot execute the join remotely. Add such quals to 'joinclauses'.
*
* Add other quals to fpinfo->remote_conds if they are shippable, else to
* fpinfo->local_conds. In an inner join it's okay to execute conditions
* either locally or remotely; the same is true for pushed-down conditions
* at an outer join.
*
* Note we might return failure after having already scribbled on
* fpinfo->remote_conds and fpinfo->local_conds. That's okay because we
* won't consult those lists again if we deem the join unshippable.
*/
joinclauses = NIL;
foreach(lc, extra->restrictlist)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
bool is_remote_clause = is_foreign_expr(root, joinrel,
rinfo->clause);
if (IS_OUTER_JOIN(jointype) &&
!RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
{
if (!is_remote_clause)
return false;
joinclauses = lappend(joinclauses, rinfo);
}
else
{
if (is_remote_clause)
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
else
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
/*
* deparseExplicitTargetList() isn't smart enough to handle anything other
* than a Var. In particular, if there's some PlaceHolderVar that would
* need to be evaluated within this join tree (because there's an upper
* reference to a quantity that may go to NULL as a result of an outer
* join), then we can't try to push the join down because we'll fail when
* we get to deparseExplicitTargetList(). However, a PlaceHolderVar that
* needs to be evaluated *at the top* of this join tree is OK, because we
* can do that locally after fetching the results from the remote side.
*/
foreach(lc, root->placeholder_list)
{
PlaceHolderInfo *phinfo = lfirst(lc);
Relids relids;
/* PlaceHolderInfo refers to parent relids, not child relids. */
relids = IS_OTHER_REL(joinrel) ?
joinrel->top_parent_relids : joinrel->relids;
if (bms_is_subset(phinfo->ph_eval_at, relids) &&
bms_nonempty_difference(relids, phinfo->ph_eval_at))
return false;
}
/* Save the join clauses, for later use. */
fpinfo->joinclauses = joinclauses;
fpinfo->outerrel = outerrel;
fpinfo->innerrel = innerrel;
fpinfo->jointype = jointype;
/*
* By default, both the input relations are not required to be deparsed as
* subqueries, but there might be some relations covered by the input
* relations that are required to be deparsed as subqueries, so save the
* relids of those relations for later use by the deparser.
*/
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
Assert(bms_is_subset(fpinfo_o->lower_subquery_rels, outerrel->relids));
Assert(bms_is_subset(fpinfo_i->lower_subquery_rels, innerrel->relids));
fpinfo->lower_subquery_rels = bms_union(fpinfo_o->lower_subquery_rels,
fpinfo_i->lower_subquery_rels);
/*
* Pull the other remote conditions from the joining relations into join
* clauses or other remote clauses (remote_conds) of this relation
* wherever possible. This avoids building subqueries at every join step.
*
* For an inner join, clauses from both the relations are added to the
* other remote clauses. For LEFT and RIGHT OUTER join, the clauses from
* the outer side are added to remote_conds since those can be evaluated
* after the join is evaluated. The clauses from inner side are added to
* the joinclauses, since they need to be evaluated while constructing the
* join.
*
* For a FULL OUTER JOIN, the other clauses from either relation can not
* be added to the joinclauses or remote_conds, since each relation acts
* as an outer relation for the other.
*
* The joining sides can not have local conditions, thus no need to test
* shippability of the clauses being pulled up.
*/
switch (jointype)
{
case JOIN_INNER:
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
fpinfo_i->remote_conds);
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
fpinfo_o->remote_conds);
break;
case JOIN_LEFT:
fpinfo->joinclauses = list_concat(fpinfo->joinclauses,
fpinfo_i->remote_conds);
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
fpinfo_o->remote_conds);
break;
case JOIN_RIGHT:
fpinfo->joinclauses = list_concat(fpinfo->joinclauses,
fpinfo_o->remote_conds);
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
fpinfo_i->remote_conds);
break;
case JOIN_FULL:
/*
* In this case, if any of the input relations has conditions, we
* need to deparse that relation as a subquery so that the
* conditions can be evaluated before the join. Remember it in
* the fpinfo of this relation so that the deparser can take
* appropriate action. Also, save the relids of base relations
* covered by that relation for later use by the deparser.
*/
if (fpinfo_o->remote_conds)
{
fpinfo->make_outerrel_subquery = true;
fpinfo->lower_subquery_rels =
bms_add_members(fpinfo->lower_subquery_rels,
outerrel->relids);
}
if (fpinfo_i->remote_conds)
{
fpinfo->make_innerrel_subquery = true;
fpinfo->lower_subquery_rels =
bms_add_members(fpinfo->lower_subquery_rels,
innerrel->relids);
}
break;
default:
/* Should not happen, we have just checked this above */
elog(ERROR, "unsupported join type %d", jointype);
}
/*
* For an inner join, all restrictions can be treated alike. Treating the
* pushed down conditions as join conditions allows a top level full outer
* join to be deparsed without requiring subqueries.
*/
if (jointype == JOIN_INNER)
{
Assert(!fpinfo->joinclauses);
fpinfo->joinclauses = fpinfo->remote_conds;
fpinfo->remote_conds = NIL;
}
/* Mark that this join can be pushed down safely */
fpinfo->pushdown_safe = true;
/* Get user mapping */
if (fpinfo->use_remote_estimate)
{
if (fpinfo_o->use_remote_estimate)
fpinfo->user = fpinfo_o->user;
else
fpinfo->user = fpinfo_i->user;
}
else
fpinfo->user = NULL;
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this join relation to be used in EXPLAIN
* output of corresponding ForeignScan.
*/
fpinfo->relation_name = makeStringInfo();
appendStringInfo(fpinfo->relation_name, "(%s) %s JOIN (%s)",
fpinfo_o->relation_name->data,
get_jointype_name(fpinfo->jointype),
fpinfo_i->relation_name->data);
/*
* Set the relation index. This is defined as the position of this
* joinrel in the join_rel_list list plus the length of the rtable list.
* Note that since this joinrel is at the end of the join_rel_list list
* when we are called, we can get the position by list_length.
*/
Assert(fpinfo->relation_index == 0); /* shouldn't be set yet */
fpinfo->relation_index =
list_length(root->parse->rtable) + list_length(root->join_rel_list);
return true;
}
static void
add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
Path *epq_path)
{
List *useful_pathkeys_list = NIL; /* List of all pathkeys */
ListCell *lc;
useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel);
/* Create one path for each set of pathkeys we found above. */
foreach(lc, useful_pathkeys_list)
{
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *useful_pathkeys = lfirst(lc);
Path *sorted_epq_path;
estimate_path_cost_size(root, rel, NIL, useful_pathkeys, NULL,
&rows, &width, &startup_cost, &total_cost);
/*
* The EPQ path must be at least as well sorted as the path itself, in
* case it gets used as input to a mergejoin.
*/
sorted_epq_path = epq_path;
if (sorted_epq_path != NULL &&
!pathkeys_contained_in(useful_pathkeys,
sorted_epq_path->pathkeys))
sorted_epq_path = (Path *)
create_sort_path(root,
rel,
sorted_epq_path,
useful_pathkeys,
-1.0);
if (IS_SIMPLE_REL(rel))
add_path(rel, (Path *)
create_foreignscan_path(root, rel,
NULL,
rows,
startup_cost,
total_cost,
useful_pathkeys,
rel->lateral_relids,
sorted_epq_path,
NIL));
else
add_path(rel, (Path *)
create_foreign_join_path(root, rel,
NULL,
rows,
startup_cost,
total_cost,
useful_pathkeys,
rel->lateral_relids,
sorted_epq_path,
NIL));
}
}
/*
* Parse options from foreign server and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void
apply_server_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc;
foreach(lc, fpinfo->server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fdw_startup_cost") == 0)
fpinfo->fdw_startup_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "fdw_tuple_cost") == 0)
fpinfo->fdw_tuple_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "extensions") == 0)
fpinfo->shippable_extensions =
ExtractExtensionList(defGetString(def), false);
else if (strcmp(def->defname, "fetch_size") == 0)
fpinfo->fetch_size = strtol(defGetString(def), NULL, 10);
}
}
/*
* Parse options from foreign table and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void
apply_table_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc;
foreach(lc, fpinfo->table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fetch_size") == 0)
fpinfo->fetch_size = strtol(defGetString(def), NULL, 10);
}
}
/*
* Merge FDW options from input relations into a new set of options for a join
* or an upper rel.
*
* For a join relation, FDW-specific information about the inner and outer
* relations is provided using fpinfo_i and fpinfo_o. For an upper relation,
* fpinfo_o provides the information for the input relation; fpinfo_i is
* expected to NULL.
*/
static void
merge_fdw_options(PgFdwRelationInfo *fpinfo,
const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i)
{
/* We must always have fpinfo_o. */
Assert(fpinfo_o);
/* fpinfo_i may be NULL, but if present the servers must both match. */
Assert(!fpinfo_i ||
fpinfo_i->server->serverid == fpinfo_o->server->serverid);
/*
* Copy the server specific FDW options. (For a join, both relations come
* from the same server, so the server options should have the same value
* for both relations.)
*/
fpinfo->fdw_startup_cost = fpinfo_o->fdw_startup_cost;
fpinfo->fdw_tuple_cost = fpinfo_o->fdw_tuple_cost;
fpinfo->shippable_extensions = fpinfo_o->shippable_extensions;
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate;
fpinfo->fetch_size = fpinfo_o->fetch_size;
/* Merge the table level options from either side of the join. */
if (fpinfo_i)
{
/*
* We'll prefer to use remote estimates for this join if any table
* from either side of the join is using remote estimates. This is
* most likely going to be preferred since they're already willing to
* pay the price of a round trip to get the remote EXPLAIN. In any
* case it's not entirely clear how we might otherwise handle this
* best.
*/
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate ||
fpinfo_i->use_remote_estimate;
/*
* Set fetch size to maximum of the joining sides, since we are
* expecting the rows returned by the join to be proportional to the
* relation sizes.
*/
fpinfo->fetch_size = Max(fpinfo_o->fetch_size, fpinfo_i->fetch_size);
}
}
/*
* postgresGetForeignJoinPaths
* Add possible ForeignPath to joinrel, if join is safe to push down.
*/
static void
postgresGetForeignJoinPaths(PlannerInfo *root,
RelOptInfo *joinrel,
RelOptInfo *outerrel,
RelOptInfo *innerrel,
JoinType jointype,
JoinPathExtraData *extra)
{
PgFdwRelationInfo *fpinfo;
ForeignPath *joinpath;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
Path *epq_path; /* Path to create plan to be executed when
* EvalPlanQual gets triggered. */
/*
* Skip if this join combination has been considered already.
*/
if (joinrel->fdw_private)
return;
/*
* This code does not work for joins with lateral references, since those
* must have parameterized paths, which we don't generate yet.
*/
if (!bms_is_empty(joinrel->lateral_relids))
return;
/*
* Create unfinished PgFdwRelationInfo entry which is used to indicate
* that the join relation is already considered, so that we won't waste
* time in judging safety of join pushdown and adding the same paths again
* if found safe. Once we know that this join can be pushed down, we fill
* the entry.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
joinrel->fdw_private = fpinfo;
/* attrs_used is only for base relations. */
fpinfo->attrs_used = NULL;
/*
* If there is a possibility that EvalPlanQual will be executed, we need
* to be able to reconstruct the row using scans of the base relations.
* GetExistingLocalJoinPath will find a suitable path for this purpose in
* the path list of the joinrel, if one exists. We must be careful to
* call it before adding any ForeignPath, since the ForeignPath might
* dominate the only suitable local path available. We also do it before
* calling foreign_join_ok(), since that function updates fpinfo and marks
* it as pushable if the join is found to be pushable.
*/
if (root->parse->commandType == CMD_DELETE ||
root->parse->commandType == CMD_UPDATE ||
root->rowMarks)
{
epq_path = GetExistingLocalJoinPath(joinrel);
if (!epq_path)
{
elog(DEBUG3, "could not push down foreign join because a local path suitable for EPQ checks was not found");
return;
}
}
else
epq_path = NULL;
if (!foreign_join_ok(root, joinrel, jointype, outerrel, innerrel, extra))
{
/* Free path required for EPQ if we copied one; we don't need it now */
if (epq_path)
pfree(epq_path);
return;
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
* The local conditions are applied after the join has been computed on
* the remote side like quals in WHERE clause, so pass jointype as
* JOIN_INNER.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
0,
JOIN_INNER,
NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* If we are going to estimate costs locally, estimate the join clause
* selectivity here while we have special join info.
*/
if (!fpinfo->use_remote_estimate)
fpinfo->joinclause_sel = clauselist_selectivity(root, fpinfo->joinclauses,
0, fpinfo->jointype,
extra->sjinfo);
/* Estimate costs for bare join relation */
estimate_path_cost_size(root, joinrel, NIL, NIL, NULL,
&rows, &width, &startup_cost, &total_cost);
/* Now update this information in the joinrel */
joinrel->rows = rows;
joinrel->reltarget->width = width;
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/*
* Create a new join path and add it to the joinrel which represents a
* join between foreign tables.
*/
joinpath = create_foreign_join_path(root,
joinrel,
NULL, /* default pathtarget */
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
joinrel->lateral_relids,
epq_path,
NIL); /* no fdw_private */
/* Add generated path into joinrel by add_path(). */
add_path(joinrel, (Path *) joinpath);
/* Consider pathkeys for the join relation */
add_paths_with_pathkeys_for_rel(root, joinrel, epq_path);
/* XXX Consider parameterized paths for the join relation */
}
/*
* Assess whether the aggregation, grouping and having operations can be pushed
* down to the foreign server. As a side effect, save information we obtain in
* this function to PgFdwRelationInfo of the input relation.
*/
static bool
foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel,
Node *havingQual)
{
Query *query = root->parse;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) grouped_rel->fdw_private;
PathTarget *grouping_target = grouped_rel->reltarget;
PgFdwRelationInfo *ofpinfo;
ListCell *lc;
int i;
List *tlist = NIL;
/* We currently don't support pushing Grouping Sets. */
if (query->groupingSets)
return false;
/* Get the fpinfo of the underlying scan relation. */
ofpinfo = (PgFdwRelationInfo *) fpinfo->outerrel->fdw_private;
/*
* If underlying scan relation has any local conditions, those conditions
* are required to be applied before performing aggregation. Hence the
* aggregate cannot be pushed down.
*/
if (ofpinfo->local_conds)
return false;
/*
* Examine grouping expressions, as well as other expressions we'd need to
* compute, and check whether they are safe to push down to the foreign
* server. All GROUP BY expressions will be part of the grouping target
* and thus there is no need to search for them separately. Add grouping
* expressions into target list which will be passed to foreign server.
*
* A tricky fine point is that we must not put any expression into the
* target list that is just a foreign param (that is, something that
* deparse.c would conclude has to be sent to the foreign server). If we
* do, the expression will also appear in the fdw_exprs list of the plan
* node, and setrefs.c will get confused and decide that the fdw_exprs
* entry is actually a reference to the fdw_scan_tlist entry, resulting in
* a broken plan. Somewhat oddly, it's OK if the expression contains such
* a node, as long as it's not at top level; then no match is possible.
*/
i = 0;
foreach(lc, grouping_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
Index sgref = get_pathtarget_sortgroupref(grouping_target, i);
ListCell *l;
/* Check whether this expression is part of GROUP BY clause */
if (sgref && get_sortgroupref_clause_noerr(sgref, query->groupClause))
{
TargetEntry *tle;
/*
* If any GROUP BY expression is not shippable, then we cannot
* push down aggregation to the foreign server.
*/
if (!is_foreign_expr(root, grouped_rel, expr))
return false;
/*
* If it would be a foreign param, we can't put it into the tlist,
* so we have to fail.
*/
if (is_foreign_param(root, grouped_rel, expr))
return false;
/*
* Pushable, so add to tlist. We need to create a TLE for this
* expression and apply the sortgroupref to it. We cannot use
* add_to_flat_tlist() here because that avoids making duplicate
* entries in the tlist. If there are duplicate entries with
* distinct sortgrouprefs, we have to duplicate that situation in
* the output tlist.
*/
tle = makeTargetEntry(expr, list_length(tlist) + 1, NULL, false);
tle->ressortgroupref = sgref;
tlist = lappend(tlist, tle);
}
else
{
/*
* Non-grouping expression we need to compute. Can we ship it
* as-is to the foreign server?
*/
if (is_foreign_expr(root, grouped_rel, expr) &&
!is_foreign_param(root, grouped_rel, expr))
{
/* Yes, so add to tlist as-is; OK to suppress duplicates */
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
else
{
/* Not pushable as a whole; extract its Vars and aggregates */
List *aggvars;
aggvars = pull_var_clause((Node *) expr,
PVC_INCLUDE_AGGREGATES);
/*
* If any aggregate expression is not shippable, then we
* cannot push down aggregation to the foreign server. (We
* don't have to check is_foreign_param, since that certainly
* won't return true for any such expression.)
*/
if (!is_foreign_expr(root, grouped_rel, (Expr *) aggvars))
return false;
/*
* Add aggregates, if any, into the targetlist. Plain Vars
* outside an aggregate can be ignored, because they should be
* either same as some GROUP BY column or part of some GROUP
* BY expression. In either case, they are already part of
* the targetlist and thus no need to add them again. In fact
* including plain Vars in the tlist when they do not match a
* GROUP BY column would cause the foreign server to complain
* that the shipped query is invalid.
*/
foreach(l, aggvars)
{
Expr *expr = (Expr *) lfirst(l);
if (IsA(expr, Aggref))
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
i++;
}
/*
* Classify the pushable and non-pushable HAVING clauses and save them in
* remote_conds and local_conds of the grouped rel's fpinfo.
*/
if (havingQual)
{
ListCell *lc;
foreach(lc, (List *) havingQual)
{
Expr *expr = (Expr *) lfirst(lc);
RestrictInfo *rinfo;
/*
* Currently, the core code doesn't wrap havingQuals in
* RestrictInfos, so we must make our own.
*/
Assert(!IsA(expr, RestrictInfo));
rinfo = make_restrictinfo(expr,
true,
false,
false,
root->qual_security_level,
grouped_rel->relids,
NULL,
NULL);
if (is_foreign_expr(root, grouped_rel, expr))
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
else
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
/*
* If there are any local conditions, pull Vars and aggregates from it and
* check whether they are safe to pushdown or not.
*/
if (fpinfo->local_conds)
{
List *aggvars = NIL;
ListCell *lc;
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
aggvars = list_concat(aggvars,
pull_var_clause((Node *) rinfo->clause,
PVC_INCLUDE_AGGREGATES));
}
foreach(lc, aggvars)
{
Expr *expr = (Expr *) lfirst(lc);
/*
* If aggregates within local conditions are not safe to push
* down, then we cannot push down the query. Vars are already
* part of GROUP BY clause which are checked above, so no need to
* access them again here. Again, we need not check
* is_foreign_param for a foreign aggregate.
*/
if (IsA(expr, Aggref))
{
if (!is_foreign_expr(root, grouped_rel, expr))
return false;
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
/* Store generated targetlist */
fpinfo->grouped_tlist = tlist;
/* Safe to pushdown */
fpinfo->pushdown_safe = true;
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this grouped relation to be used in EXPLAIN
* output of corresponding ForeignScan.
*/
fpinfo->relation_name = makeStringInfo();
appendStringInfo(fpinfo->relation_name, "Aggregate on (%s)",
ofpinfo->relation_name->data);
return true;
}
/*
* postgresGetForeignUpperPaths
* Add paths for post-join operations like aggregation, grouping etc. if
* corresponding operations are safe to push down.
*/
static void
postgresGetForeignUpperPaths(PlannerInfo *root, UpperRelationKind stage,
RelOptInfo *input_rel, RelOptInfo *output_rel,
void *extra)
{
PgFdwRelationInfo *fpinfo;
/*
* If input rel is not safe to pushdown, then simply return as we cannot
* perform any post-join operations on the foreign server.
*/
if (!input_rel->fdw_private ||
!((PgFdwRelationInfo *) input_rel->fdw_private)->pushdown_safe)
return;
/* Ignore stages we don't support; and skip any duplicate calls. */
if ((stage != UPPERREL_GROUP_AGG &&
stage != UPPERREL_ORDERED &&
stage != UPPERREL_FINAL) ||
output_rel->fdw_private)
return;
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
fpinfo->stage = stage;
output_rel->fdw_private = fpinfo;
switch (stage)
{
case UPPERREL_GROUP_AGG:
add_foreign_grouping_paths(root, input_rel, output_rel,
(GroupPathExtraData *) extra);
break;
case UPPERREL_ORDERED:
add_foreign_ordered_paths(root, input_rel, output_rel);
break;
case UPPERREL_FINAL:
add_foreign_final_paths(root, input_rel, output_rel,
(FinalPathExtraData *) extra);
break;
default:
elog(ERROR, "unexpected upper relation: %d", (int) stage);
break;
}
}
/*
* add_foreign_grouping_paths
* Add foreign path for grouping and/or aggregation.
*
* Given input_rel represents the underlying scan. The paths are added to the
* given grouped_rel.
*/
static void
add_foreign_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *grouped_rel,
GroupPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = grouped_rel->fdw_private;
ForeignPath *grouppath;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Nothing to be done, if there is no grouping or aggregation required. */
if (!parse->groupClause && !parse->groupingSets && !parse->hasAggs &&
!root->hasHavingQual)
return;
Assert(extra->patype == PARTITIONWISE_AGGREGATE_NONE ||
extra->patype == PARTITIONWISE_AGGREGATE_FULL);
/* save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* Assess if it is safe to push down aggregation and grouping.
*
* Use HAVING qual from extra. In case of child partition, it will have
* translated Vars.
*/
if (!foreign_grouping_ok(root, grouped_rel, extra->havingQual))
return;
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. (Currently we create just a single
* path here, but in future it would be possible that we build more paths
* such as pre-sorted paths as in postgresGetForeignPaths and
* postgresGetForeignJoinPaths.) The best we can do for these conditions
* is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
0,
JOIN_INNER,
NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/* Estimate the cost of push down */
estimate_path_cost_size(root, grouped_rel, NIL, NIL, NULL,
&rows, &width, &startup_cost, &total_cost);
/* Now update this information in the fpinfo */
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/* Create and add foreign path to the grouping relation. */
grouppath = create_foreign_upper_path(root,
grouped_rel,
grouped_rel->reltarget,
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
NULL,
NIL); /* no fdw_private */
/* Add generated path into grouped_rel by add_path(). */
add_path(grouped_rel, (Path *) grouppath);
}
/*
* add_foreign_ordered_paths
* Add foreign paths for performing the final sort remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given ordered_rel.
*/
static void
add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *ordered_rel)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = ordered_rel->fdw_private;
PgFdwPathExtraData *fpextra;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
ForeignPath *ordered_path;
ListCell *lc;
/* Shouldn't get here unless the query has ORDER BY */
Assert(parse->sortClause);
/* We don't support cases where there are any SRFs in the targetlist */
if (parse->hasTargetSRFs)
return;
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If the input_rel is a base or join relation, we would already have
* considered pushing down the final sort to the remote server when
* creating pre-sorted foreign paths for that relation, because the
* query_pathkeys is set to the root->sort_pathkeys in that case (see
* standard_qp_callback()).
*/
if (input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL)
{
Assert(root->query_pathkeys == root->sort_pathkeys);
/* Safe to push down if the query_pathkeys is safe to push down */
fpinfo->pushdown_safe = ifpinfo->qp_is_pushdown_safe;
return;
}
/* The input_rel should be a grouping relation */
Assert(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_GROUP_AGG);
/*
* We try to create a path below by extending a simple foreign path for
* the underlying grouping relation to perform the final sort remotely,
* which is stored into the fdw_private list of the resulting path.
*/
/* Assess if it is safe to push down the final sort */
foreach(lc, root->sort_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
Expr *sort_expr;
/*
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
if (pathkey_ec->ec_has_volatile)
return;
/* Get the sort expression for the pathkey_ec */
sort_expr = find_em_expr_for_input_target(root,
pathkey_ec,
input_rel->reltarget);
/* If it's unsafe to remote, we cannot push down the final sort */
if (!is_foreign_expr(root, input_rel, sort_expr))
return;
}
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *) palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = root->upper_targets[UPPERREL_ORDERED];
fpextra->has_final_sort = true;
/* Estimate the costs of performing the final sort remotely */
estimate_path_cost_size(root, input_rel, NIL, root->sort_pathkeys, fpextra,
&rows, &width, &startup_cost, &total_cost);
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(true), makeInteger(false));
/* Create foreign ordering path */
ordered_path = create_foreign_upper_path(root,
input_rel,
root->upper_targets[UPPERREL_ORDERED],
rows,
startup_cost,
total_cost,
root->sort_pathkeys,
NULL, /* no extra plan */
fdw_private);
/* and add it to the ordered_rel */
add_path(ordered_rel, (Path *) ordered_path);
}
/*
* add_foreign_final_paths
* Add foreign paths for performing the final processing remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given final_rel.
*/
static void
add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *final_rel,
FinalPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = (PgFdwRelationInfo *) input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) final_rel->fdw_private;
bool has_final_sort = false;
List *pathkeys = NIL;
PgFdwPathExtraData *fpextra;
bool save_use_remote_estimate = false;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
ForeignPath *final_path;
/*
* Currently, we only support this for SELECT commands
*/
if (parse->commandType != CMD_SELECT)
return;
/*
* No work if there is no FOR UPDATE/SHARE clause and if there is no need
* to add a LIMIT node
*/
if (!parse->rowMarks && !extra->limit_needed)
return;
/* We don't support cases where there are any SRFs in the targetlist */
if (parse->hasTargetSRFs)
return;
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If there is no need to add a LIMIT node, there might be a ForeignPath
* in the input_rel's pathlist that implements all behavior of the query.
* Note: we would already have accounted for the query's FOR UPDATE/SHARE
* (if any) before we get here.
*/
if (!extra->limit_needed)
{
ListCell *lc;
Assert(parse->rowMarks);
/*
* Grouping and aggregation are not supported with FOR UPDATE/SHARE,
* so the input_rel should be a base, join, or ordered relation; and
* if it's an ordered relation, its input relation should be a base or
* join relation.
*/
Assert(input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_ORDERED &&
(ifpinfo->outerrel->reloptkind == RELOPT_BASEREL ||
ifpinfo->outerrel->reloptkind == RELOPT_JOINREL)));
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
/*
* apply_scanjoin_target_to_paths() uses create_projection_path()
* to adjust each of its input paths if needed, whereas
* create_ordered_paths() uses apply_projection_to_path() to do
* that. So the former might have put a ProjectionPath on top of
* the ForeignPath; look through ProjectionPath and see if the
* path underneath it is ForeignPath.
*/
if (IsA(path, ForeignPath) ||
(IsA(path, ProjectionPath) &&
IsA(((ProjectionPath *) path)->subpath, ForeignPath)))
{
/*
* Create foreign final path; this gets rid of a
* no-longer-needed outer plan (if any), which makes the
* EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root,
path->parent,
path->pathtarget,
path->rows,
path->startup_cost,
path->total_cost,
path->pathkeys,
NULL, /* no extra plan */
NULL); /* no fdw_private */
/* and add it to the final_rel */
add_path(final_rel, (Path *) final_path);
/* Safe to push down */
fpinfo->pushdown_safe = true;
return;
}
}
/*
* If we get here it means no ForeignPaths; since we would already
* have considered pushing down all operations for the query to the
* remote server, give up on it.
*/
return;
}
Assert(extra->limit_needed);
/*
* If the input_rel is an ordered relation, replace the input_rel with its
* input relation
*/
if (input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_ORDERED)
{
input_rel = ifpinfo->outerrel;
ifpinfo = (PgFdwRelationInfo *) input_rel->fdw_private;
has_final_sort = true;
pathkeys = root->sort_pathkeys;
}
/* The input_rel should be a base, join, or grouping relation */
Assert(input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_GROUP_AGG));
/*
* We try to create a path below by extending a simple foreign path for
* the underlying base, join, or grouping relation to perform the final
* sort (if has_final_sort) and the LIMIT restriction remotely, which is
* stored into the fdw_private list of the resulting path. (We
* re-estimate the costs of sorting the underlying relation, if
* has_final_sort.)
*/
/*
* Assess if it is safe to push down the LIMIT and OFFSET to the remote
* server
*/
/*
* If the underlying relation has any local conditions, the LIMIT/OFFSET
* cannot be pushed down.
*/
if (ifpinfo->local_conds)
return;
/*
* Also, the LIMIT/OFFSET cannot be pushed down, if their expressions are
* not safe to remote.
*/
if (!is_foreign_expr(root, input_rel, (Expr *) parse->limitOffset) ||
!is_foreign_expr(root, input_rel, (Expr *) parse->limitCount))
return;
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *) palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = root->upper_targets[UPPERREL_FINAL];
fpextra->has_final_sort = has_final_sort;
fpextra->has_limit = extra->limit_needed;
fpextra->limit_tuples = extra->limit_tuples;
fpextra->count_est = extra->count_est;
fpextra->offset_est = extra->offset_est;
/*
* Estimate the costs of performing the final sort and the LIMIT
* restriction remotely. If has_final_sort is false, we wouldn't need to
* execute EXPLAIN anymore if use_remote_estimate, since the costs can be
* roughly estimated using the costs we already have for the underlying
* relation, in the same way as when use_remote_estimate is false. Since
* it's pretty expensive to execute EXPLAIN, force use_remote_estimate to
* false in that case.
*/
if (!fpextra->has_final_sort)
{
save_use_remote_estimate = ifpinfo->use_remote_estimate;
ifpinfo->use_remote_estimate = false;
}
estimate_path_cost_size(root, input_rel, NIL, pathkeys, fpextra,
&rows, &width, &startup_cost, &total_cost);
if (!fpextra->has_final_sort)
ifpinfo->use_remote_estimate = save_use_remote_estimate;
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(has_final_sort),
makeInteger(extra->limit_needed));
/*
* Create foreign final path; this gets rid of a no-longer-needed outer
* plan (if any), which makes the EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root,
input_rel,
root->upper_targets[UPPERREL_FINAL],
rows,
startup_cost,
total_cost,
pathkeys,
NULL, /* no extra plan */
fdw_private);
/* and add it to the final_rel */
add_path(final_rel, (Path *) final_path);
}
/*
* Create a tuple from the specified row of the PGresult.
*
* rel is the local representation of the foreign table, attinmeta is
* conversion data for the rel's tupdesc, and retrieved_attrs is an
* integer list of the table column numbers present in the PGresult.
* temp_context is a working context that can be reset after each tuple.
*/
static HeapTuple
make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
ForeignScanState *fsstate,
MemoryContext temp_context)
{
HeapTuple tuple;
TupleDesc tupdesc;
Datum *values;
bool *nulls;
ItemPointer ctid = NULL;
ConversionLocation errpos;
ErrorContextCallback errcallback;
MemoryContext oldcontext;
ListCell *lc;
int j;
Assert(row < PQntuples(res));
/*
* Do the following work in a temp context that we reset after each tuple.
* This cleans up not only the data we have direct access to, but any
* cruft the I/O functions might leak.
*/
oldcontext = MemoryContextSwitchTo(temp_context);
if (rel)
tupdesc = RelationGetDescr(rel);
else
{
Assert(fsstate);
tupdesc = fsstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
}
values = (Datum *) palloc0(tupdesc->natts * sizeof(Datum));
nulls = (bool *) palloc(tupdesc->natts * sizeof(bool));
/* Initialize to nulls for any columns not present in result */
memset(nulls, true, tupdesc->natts * sizeof(bool));
/*
* Set up and install callback to report where conversion error occurs.
*/
errpos.rel = rel;
errpos.cur_attno = 0;
errpos.fsstate = fsstate;
errcallback.callback = conversion_error_callback;
errcallback.arg = (void *) &errpos;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
/*
* i indexes columns in the relation, j indexes columns in the PGresult.
*/
j = 0;
foreach(lc, retrieved_attrs)
{
int i = lfirst_int(lc);
char *valstr;
/* fetch next column's textual value */
if (PQgetisnull(res, row, j))
valstr = NULL;
else
valstr = PQgetvalue(res, row, j);
/*
* convert value to internal representation
*
* Note: we ignore system columns other than ctid and oid in result
*/
errpos.cur_attno = i;
if (i > 0)
{
/* ordinary column */
Assert(i <= tupdesc->natts);
nulls[i - 1] = (valstr == NULL);
/* Apply the input function even to nulls, to support domains */
values[i - 1] = InputFunctionCall(&attinmeta->attinfuncs[i - 1],
valstr,
attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
}
else if (i == SelfItemPointerAttributeNumber)
{
/* ctid */
if (valstr != NULL)
{
Datum datum;
datum = DirectFunctionCall1(tidin, CStringGetDatum(valstr));
ctid = (ItemPointer) DatumGetPointer(datum);
}
}
errpos.cur_attno = 0;
j++;
}
/* Uninstall error context callback. */
error_context_stack = errcallback.previous;
/*
* Check we got the expected number of columns. Note: j == 0 and
* PQnfields == 1 is expected, since deparse emits a NULL if no columns.
*/
if (j > 0 && j != PQnfields(res))
elog(ERROR, "remote query result does not match the foreign table");
/*
* Build the result tuple in caller's memory context.
*/
MemoryContextSwitchTo(oldcontext);
tuple = heap_form_tuple(tupdesc, values, nulls);
/*
* If we have a CTID to return, install it in both t_self and t_ctid.
* t_self is the normal place, but if the tuple is converted to a
* composite Datum, t_self will be lost; setting t_ctid allows CTID to be
* preserved during EvalPlanQual re-evaluations (see ROW_MARK_COPY code).
*/
if (ctid)
tuple->t_self = tuple->t_data->t_ctid = *ctid;
/*
* Stomp on the xmin, xmax, and cmin fields from the tuple created by
* heap_form_tuple. heap_form_tuple actually creates the tuple with
* DatumTupleFields, not HeapTupleFields, but the executor expects
* HeapTupleFields and will happily extract system columns on that
* assumption. If we don't do this then, for example, the tuple length
* ends up in the xmin field, which isn't what we want.
*/
HeapTupleHeaderSetXmax(tuple->t_data, InvalidTransactionId);
HeapTupleHeaderSetXmin(tuple->t_data, InvalidTransactionId);
HeapTupleHeaderSetCmin(tuple->t_data, InvalidTransactionId);
/* Clean up */
MemoryContextReset(temp_context);
return tuple;
}
/*
* Callback function which is called when error occurs during column value
* conversion. Print names of column and relation.
*/
static void
conversion_error_callback(void *arg)
{
const char *attname = NULL;
const char *relname = NULL;
bool is_wholerow = false;
ConversionLocation *errpos = (ConversionLocation *) arg;
if (errpos->rel)
{
/* error occurred in a scan against a foreign table */
TupleDesc tupdesc = RelationGetDescr(errpos->rel);
Form_pg_attribute attr = TupleDescAttr(tupdesc, errpos->cur_attno - 1);
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
attname = NameStr(attr->attname);
else if (errpos->cur_attno == SelfItemPointerAttributeNumber)
attname = "ctid";
relname = RelationGetRelationName(errpos->rel);
}
else
{
/* error occurred in a scan against a foreign join */
ForeignScanState *fsstate = errpos->fsstate;
ForeignScan *fsplan = castNode(ForeignScan, fsstate->ss.ps.plan);
EState *estate = fsstate->ss.ps.state;
TargetEntry *tle;
tle = list_nth_node(TargetEntry, fsplan->fdw_scan_tlist,
errpos->cur_attno - 1);
/*
* Target list can have Vars and expressions. For Vars, we can get
* its relation, however for expressions we can't. Thus for
* expressions, just show generic context message.
*/
if (IsA(tle->expr, Var))
{
RangeTblEntry *rte;
Var *var = (Var *) tle->expr;
rte = exec_rt_fetch(var->varno, estate);
if (var->varattno == 0)
is_wholerow = true;
else
attname = get_attname(rte->relid, var->varattno, false);
relname = get_rel_name(rte->relid);
}
else
errcontext("processing expression at position %d in select list",
errpos->cur_attno);
}
if (relname)
{
if (is_wholerow)
errcontext("whole-row reference to foreign table \"%s\"", relname);
else if (attname)
errcontext("column \"%s\" of foreign table \"%s\"", attname, relname);
}
}
/*
* Find an equivalence class member expression, all of whose Vars, come from
* the indicated relation.
*/
Expr *
find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
{
ListCell *lc_em;
foreach(lc_em, ec->ec_members)
{
EquivalenceMember *em = lfirst(lc_em);
if (bms_is_subset(em->em_relids, rel->relids) &&
!bms_is_empty(em->em_relids))
{
/*
* If there is more than one equivalence member whose Vars are
* taken entirely from this relation, we'll be content to choose
* any one of those.
*/
return em->em_expr;
}
}
/* We didn't find any suitable equivalence class expression */
return NULL;
}
/*
* Find an equivalence class member expression to be computed as a sort column
* in the given target.
*/
Expr *
find_em_expr_for_input_target(PlannerInfo *root,
EquivalenceClass *ec,
PathTarget *target)
{
ListCell *lc1;
int i;
i = 0;
foreach(lc1, target->exprs)
{
Expr *expr = (Expr *) lfirst(lc1);
Index sgref = get_pathtarget_sortgroupref(target, i);
ListCell *lc2;
/* Ignore non-sort expressions */
if (sgref == 0 ||
get_sortgroupref_clause_noerr(sgref,
root->parse->sortClause) == NULL)
{
i++;
continue;
}
/* We ignore binary-compatible relabeling on both ends */
while (expr && IsA(expr, RelabelType))
expr = ((RelabelType *) expr)->arg;
/* Locate an EquivalenceClass member matching this expr, if any */
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
Expr *em_expr;
/* Don't match constants */
if (em->em_is_const)
continue;
/* Ignore child members */
if (em->em_is_child)
continue;
/* Match if same expression (after stripping relabel) */
em_expr = em->em_expr;
while (em_expr && IsA(em_expr, RelabelType))
em_expr = ((RelabelType *) em_expr)->arg;
if (equal(em_expr, expr))
return em->em_expr;
}
i++;
}
elog(ERROR, "could not find pathkey item to sort");
return NULL; /* keep compiler quiet */
}
Reference in New Issue View Git Blame Copy Permalink