From c83c22d05327805d4014088e70ae20d0284e7adf Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Mon, 14 Jun 2010 20:50:04 +0000 Subject: [PATCH] Rearrange dblink's dblink_build_sql_insert() and related routines to open and lock the target relation just once per SQL function call. The original coding obtained and released lock several times per call. Aside from saving a not-insignificant number of cycles, this eliminates possible race conditions if someone tries to modify the relation's schema concurrently. Also centralize locking and permission-checking logic. Problem noted while investigating a trouble report from Robert Voinea --- his problem is still to be fixed, though. --- contrib/dblink/dblink.c | 208 +++++++++++++++++----------------------- 1 file changed, 86 insertions(+), 122 deletions(-) diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c index 4cc7b1e4a3..15d00d888c 100644 --- a/contrib/dblink/dblink.c +++ b/contrib/dblink/dblink.c @@ -52,6 +52,7 @@ #include "tcop/tcopprot.h" #include "utils/builtins.h" #include "utils/fmgroids.h" +#include "utils/acl.h" #include "utils/array.h" #include "utils/lsyscache.h" #include "utils/syscache.h" @@ -75,19 +76,19 @@ static remoteConn *getConnectionByName(const char *name); static HTAB *createConnHash(void); static void createNewConnection(const char *name, remoteConn * con); static void deleteConnection(const char *name); -static char **get_pkey_attnames(Oid relid, int16 *numatts); -static char *get_sql_insert(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals); -static char *get_sql_delete(Oid relid, int16 *pkattnums, int16 pknumatts, char **tgt_pkattvals); -static char *get_sql_update(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals); +static char **get_pkey_attnames(Relation rel, int16 *numatts); +static char *get_sql_insert(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals); +static char *get_sql_delete(Relation rel, int16 *pkattnums, int16 pknumatts, char **tgt_pkattvals); +static char *get_sql_update(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals); static char *quote_literal_cstr(char *rawstr); static char *quote_ident_cstr(char *rawstr); static int16 get_attnum_pk_pos(int16 *pkattnums, int16 pknumatts, int16 key); -static HeapTuple get_tuple_of_interest(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals); -static Oid get_relid_from_relname(text *relname_text); -static char *generate_relation_name(Oid relid); +static HeapTuple get_tuple_of_interest(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals); +static Relation get_rel_from_relname(text *relname_text, LOCKMODE lockmode, AclMode aclmode); +static char *generate_relation_name(Relation rel); static char *connstr_strip_password(const char *connstr); static void dblink_security_check(PGconn *conn, remoteConn *rcon, const char *connstr); -static int get_nondropped_natts(Oid relid); +static int get_nondropped_natts(Relation rel); /* Global */ List *res_id = NIL; @@ -984,7 +985,6 @@ Datum dblink_get_pkey(PG_FUNCTION_ARGS) { int16 numatts; - Oid relid; char **results; FuncCallContext *funcctx; int32 call_cntr; @@ -995,7 +995,8 @@ dblink_get_pkey(PG_FUNCTION_ARGS) /* stuff done only on the first call of the function */ if (SRF_IS_FIRSTCALL()) { - TupleDesc tupdesc = NULL; + Relation rel; + TupleDesc tupdesc; /* create a function context for cross-call persistence */ funcctx = SRF_FIRSTCALL_INIT(); @@ -1006,13 +1007,13 @@ dblink_get_pkey(PG_FUNCTION_ARGS) */ oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); - /* convert relname to rel Oid */ - relid = get_relid_from_relname(PG_GETARG_TEXT_P(0)); - if (!OidIsValid(relid)) - ereport(ERROR, - (errcode(ERRCODE_UNDEFINED_TABLE), - errmsg("relation \"%s\" does not exist", - GET_STR(PG_GETARG_TEXT_P(0))))); + /* open target relation */ + rel = get_rel_from_relname(PG_GETARG_TEXT_P(0), AccessShareLock, ACL_SELECT); + + /* get the array of attnums */ + results = get_pkey_attnames(rel, &numatts); + + relation_close(rel, AccessShareLock); /* * need a tuple descriptor representing one INT and one TEXT @@ -1031,9 +1032,6 @@ dblink_get_pkey(PG_FUNCTION_ARGS) attinmeta = TupleDescGetAttInMetadata(tupdesc); funcctx->attinmeta = attinmeta; - /* get an array of attnums */ - results = get_pkey_attnames(relid, &numatts); - if ((results != NULL) && (numatts > 0)) { funcctx->max_calls = numatts; @@ -1115,7 +1113,7 @@ PG_FUNCTION_INFO_V1(dblink_build_sql_insert); Datum dblink_build_sql_insert(PG_FUNCTION_ARGS) { - Oid relid; + Relation rel; text *relname_text; int16 *pkattnums; int pknumatts_tmp; @@ -1141,14 +1139,9 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS) relname_text = PG_GETARG_TEXT_P(0); /* - * Convert relname to rel OID. + * Open target relation. */ - relid = get_relid_from_relname(relname_text); - if (!OidIsValid(relid)) - ereport(ERROR, - (errcode(ERRCODE_UNDEFINED_TABLE), - errmsg("relation \"%s\" does not exist", - GET_STR(relname_text)))); + rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT); pkattnums = (int16 *) PG_GETARG_POINTER(1); pknumatts_tmp = PG_GETARG_INT32(2); @@ -1175,7 +1168,7 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS) * ensure we don't ask for more pk attributes than we have * non-dropped columns */ - nondropped_natts = get_nondropped_natts(relid); + nondropped_natts = get_nondropped_natts(rel); if (pknumatts > nondropped_natts) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("number of primary key fields exceeds number of specified relation attributes"))); @@ -1249,7 +1242,12 @@ dblink_build_sql_insert(PG_FUNCTION_ARGS) /* * Prep work is finally done. Go get the SQL string. */ - sql = get_sql_insert(relid, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals); + sql = get_sql_insert(rel, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals); + + /* + * Now we can close the relation. + */ + relation_close(rel, AccessShareLock); /* * And send it @@ -1277,7 +1275,7 @@ PG_FUNCTION_INFO_V1(dblink_build_sql_delete); Datum dblink_build_sql_delete(PG_FUNCTION_ARGS) { - Oid relid; + Relation rel; text *relname_text; int16 *pkattnums; int pknumatts_tmp; @@ -1298,14 +1296,9 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS) relname_text = PG_GETARG_TEXT_P(0); /* - * Convert relname to rel OID. + * Open target relation. */ - relid = get_relid_from_relname(relname_text); - if (!OidIsValid(relid)) - ereport(ERROR, - (errcode(ERRCODE_UNDEFINED_TABLE), - errmsg("relation \"%s\" does not exist", - GET_STR(relname_text)))); + rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT); pkattnums = (int16 *) PG_GETARG_POINTER(1); pknumatts_tmp = PG_GETARG_INT32(2); @@ -1331,7 +1324,7 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS) * ensure we don't ask for more pk attributes than we have * non-dropped columns */ - nondropped_natts = get_nondropped_natts(relid); + nondropped_natts = get_nondropped_natts(rel); if (pknumatts > nondropped_natts) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("number of primary key fields exceeds number of specified relation attributes"))); @@ -1372,7 +1365,12 @@ dblink_build_sql_delete(PG_FUNCTION_ARGS) /* * Prep work is finally done. Go get the SQL string. */ - sql = get_sql_delete(relid, pkattnums, pknumatts, tgt_pkattvals); + sql = get_sql_delete(rel, pkattnums, pknumatts, tgt_pkattvals); + + /* + * Now we can close the relation. + */ + relation_close(rel, AccessShareLock); /* * And send it @@ -1404,7 +1402,7 @@ PG_FUNCTION_INFO_V1(dblink_build_sql_update); Datum dblink_build_sql_update(PG_FUNCTION_ARGS) { - Oid relid; + Relation rel; text *relname_text; int16 *pkattnums; int pknumatts_tmp; @@ -1430,14 +1428,9 @@ dblink_build_sql_update(PG_FUNCTION_ARGS) relname_text = PG_GETARG_TEXT_P(0); /* - * Convert relname to rel OID. + * Open target relation. */ - relid = get_relid_from_relname(relname_text); - if (!OidIsValid(relid)) - ereport(ERROR, - (errcode(ERRCODE_UNDEFINED_TABLE), - errmsg("relation \"%s\" does not exist", - GET_STR(relname_text)))); + rel = get_rel_from_relname(relname_text, AccessShareLock, ACL_SELECT); pkattnums = (int16 *) PG_GETARG_POINTER(1); pknumatts_tmp = PG_GETARG_INT32(2); @@ -1464,7 +1457,7 @@ dblink_build_sql_update(PG_FUNCTION_ARGS) * ensure we don't ask for more pk attributes than we have * non-dropped columns */ - nondropped_natts = get_nondropped_natts(relid); + nondropped_natts = get_nondropped_natts(rel); if (pknumatts > nondropped_natts) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("number of primary key fields exceeds number of specified relation attributes"))); @@ -1538,7 +1531,12 @@ dblink_build_sql_update(PG_FUNCTION_ARGS) /* * Prep work is finally done. Go get the SQL string. */ - sql = get_sql_update(relid, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals); + sql = get_sql_update(rel, pkattnums, pknumatts, src_pkattvals, tgt_pkattvals); + + /* + * Now we can close the relation. + */ + relation_close(rel, AccessShareLock); /* * And send it @@ -1572,7 +1570,7 @@ dblink_current_query(PG_FUNCTION_ARGS) * Return NULL, and set numatts = 0, if no primary key exists. */ static char ** -get_pkey_attnames(Oid relid, int16 *numatts) +get_pkey_attnames(Relation rel, int16 *numatts) { Relation indexRelation; ScanKeyData entry; @@ -1580,22 +1578,19 @@ get_pkey_attnames(Oid relid, int16 *numatts) HeapTuple indexTuple; int i; char **result = NULL; - Relation rel; TupleDesc tupdesc; - /* open relation using relid, get tupdesc */ - rel = relation_open(relid, AccessShareLock); - tupdesc = rel->rd_att; - /* initialize numatts to 0 in case no primary key exists */ *numatts = 0; + tupdesc = rel->rd_att; + /* use relid to get all related indexes */ indexRelation = heap_openr(IndexRelationName, AccessShareLock); ScanKeyInit(&entry, Anum_pg_index_indrelid, BTEqualStrategyNumber, F_OIDEQ, - ObjectIdGetDatum(relid)); + ObjectIdGetDatum(RelationGetRelid(rel))); scan = heap_beginscan(indexRelation, SnapshotNow, 1, &entry); while ((indexTuple = heap_getnext(scan, ForwardScanDirection)) != NULL) @@ -1621,15 +1616,13 @@ get_pkey_attnames(Oid relid, int16 *numatts) } heap_endscan(scan); heap_close(indexRelation, AccessShareLock); - relation_close(rel, AccessShareLock); return result; } static char * -get_sql_insert(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals) +get_sql_insert(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals) { - Relation rel; char *relname; HeapTuple tuple; TupleDesc tupdesc; @@ -1642,16 +1635,12 @@ get_sql_insert(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattval bool needComma; /* get relation name including any needed schema prefix and quoting */ - relname = generate_relation_name(relid); + relname = generate_relation_name(rel); - /* - * Open relation using relid - */ - rel = relation_open(relid, AccessShareLock); tupdesc = rel->rd_att; natts = tupdesc->natts; - tuple = get_tuple_of_interest(relid, pkattnums, pknumatts, src_pkattvals); + tuple = get_tuple_of_interest(rel, pkattnums, pknumatts, src_pkattvals); if (!tuple) ereport(ERROR, (errcode(ERRCODE_CARDINALITY_VIOLATION), @@ -1711,15 +1700,13 @@ get_sql_insert(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattval sql = pstrdup(str->data); pfree(str->data); pfree(str); - relation_close(rel, AccessShareLock); return (sql); } static char * -get_sql_delete(Oid relid, int16 *pkattnums, int16 pknumatts, char **tgt_pkattvals) +get_sql_delete(Relation rel, int16 *pkattnums, int16 pknumatts, char **tgt_pkattvals) { - Relation rel; char *relname; TupleDesc tupdesc; int natts; @@ -1729,12 +1716,8 @@ get_sql_delete(Oid relid, int16 *pkattnums, int16 pknumatts, char **tgt_pkattval int i; /* get relation name including any needed schema prefix and quoting */ - relname = generate_relation_name(relid); + relname = generate_relation_name(rel); - /* - * Open relation using relid - */ - rel = relation_open(relid, AccessShareLock); tupdesc = rel->rd_att; natts = tupdesc->natts; @@ -1767,15 +1750,13 @@ get_sql_delete(Oid relid, int16 *pkattnums, int16 pknumatts, char **tgt_pkattval sql = pstrdup(str->data); pfree(str->data); pfree(str); - relation_close(rel, AccessShareLock); return (sql); } static char * -get_sql_update(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals) +get_sql_update(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals, char **tgt_pkattvals) { - Relation rel; char *relname; HeapTuple tuple; TupleDesc tupdesc; @@ -1788,16 +1769,12 @@ get_sql_update(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattval bool needComma; /* get relation name including any needed schema prefix and quoting */ - relname = generate_relation_name(relid); + relname = generate_relation_name(rel); - /* - * Open relation using relid - */ - rel = relation_open(relid, AccessShareLock); tupdesc = rel->rd_att; natts = tupdesc->natts; - tuple = get_tuple_of_interest(relid, pkattnums, pknumatts, src_pkattvals); + tuple = get_tuple_of_interest(rel, pkattnums, pknumatts, src_pkattvals); if (!tuple) ereport(ERROR, (errcode(ERRCODE_CARDINALITY_VIOLATION), @@ -1866,7 +1843,6 @@ get_sql_update(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattval sql = pstrdup(str->data); pfree(str->data); pfree(str); - relation_close(rel, AccessShareLock); return (sql); } @@ -1923,9 +1899,8 @@ get_attnum_pk_pos(int16 *pkattnums, int16 pknumatts, int16 key) } static HeapTuple -get_tuple_of_interest(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_pkattvals) +get_tuple_of_interest(Relation rel, int16 *pkattnums, int16 pknumatts, char **src_pkattvals) { - Relation rel; char *relname; TupleDesc tupdesc; StringInfo str = makeStringInfo(); @@ -1936,14 +1911,9 @@ get_tuple_of_interest(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_p char *val = NULL; /* get relation name including any needed schema prefix and quoting */ - relname = generate_relation_name(relid); + relname = generate_relation_name(rel); - /* - * Open relation using relid - */ - rel = relation_open(relid, AccessShareLock); - tupdesc = CreateTupleDescCopy(rel->rd_att); - relation_close(rel, AccessShareLock); + tupdesc = rel->rd_att; /* * Connect to SPI manager @@ -2021,52 +1991,49 @@ get_tuple_of_interest(Oid relid, int16 *pkattnums, int16 pknumatts, char **src_p return NULL; } -static Oid -get_relid_from_relname(text *relname_text) +/* + * Open the relation named by relname_text, acquire specified type of lock, + * verify we have specified permissions. + * Caller must close rel when done with it. + */ +static Relation +get_rel_from_relname(text *relname_text, LOCKMODE lockmode, AclMode aclmode) { RangeVar *relvar; Relation rel; - Oid relid; + AclResult aclresult; - relvar = makeRangeVarFromNameList(textToQualifiedNameList(relname_text, "get_relid_from_relname")); - rel = heap_openrv(relvar, AccessShareLock); - relid = RelationGetRelid(rel); - relation_close(rel, AccessShareLock); + relvar = makeRangeVarFromNameList(textToQualifiedNameList(relname_text, "get_rel_from_relname")); + rel = heap_openrv(relvar, lockmode); - return relid; + aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(), + aclmode); + if (aclresult != ACLCHECK_OK) + aclcheck_error(aclresult, ACL_KIND_CLASS, + RelationGetRelationName(rel)); + + return rel; } /* * generate_relation_name - copied from ruleutils.c - * Compute the name to display for a relation specified by OID + * Compute the name to display for a relation * * The result includes all necessary quoting and schema-prefixing. */ static char * -generate_relation_name(Oid relid) +generate_relation_name(Relation rel) { - HeapTuple tp; - Form_pg_class reltup; char *nspname; char *result; - tp = SearchSysCache(RELOID, - ObjectIdGetDatum(relid), - 0, 0, 0); - if (!HeapTupleIsValid(tp)) - elog(ERROR, "cache lookup failed for relation %u", relid); - - reltup = (Form_pg_class) GETSTRUCT(tp); - /* Qualify the name if not visible in search path */ - if (RelationIsVisible(relid)) + if (RelationIsVisible(RelationGetRelid(rel))) nspname = NULL; else - nspname = get_namespace_name(reltup->relnamespace); + nspname = get_namespace_name(rel->rd_rel->relnamespace); - result = quote_qualified_identifier(nspname, NameStr(reltup->relname)); - - ReleaseSysCache(tp); + result = quote_qualified_identifier(nspname, RelationGetRelationName(rel)); return result; } @@ -2315,15 +2282,13 @@ dblink_security_check(PGconn *conn, remoteConn *rcon, const char *connstr) } static int -get_nondropped_natts(Oid relid) +get_nondropped_natts(Relation rel) { int nondropped_natts = 0; TupleDesc tupdesc; - Relation rel; int natts; int i; - rel = relation_open(relid, AccessShareLock); tupdesc = rel->rd_att; natts = tupdesc->natts; @@ -2334,6 +2299,5 @@ get_nondropped_natts(Oid relid) nondropped_natts++; } - relation_close(rel, AccessShareLock); return nondropped_natts; }