mirror/postgresql
2
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2025-02-05 19:09:58 +08:00
Code Issues Packages Projects Releases Wiki Activity

pg_dump: Lock all relations, not just plain tables

Browse Source 
Now that LOCK TABLE can take any relation type, acquire lock on all
relations that are to be dumped.  This prevents schema changes or
deadlock errors that could cause a dump to fail after expending much
effort.  The server is tested to have the capability and the feature
disabled if it doesn't, so that a patched pg_dump doesn't fail when
connecting to an unpatched server.

Backpatch to 9.5.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reported-by: Wells Oliver <wells.oliver@gmail.com>
Discussion: https://postgr.es/m/20201021200659.GA32358@alvherre.pgsql
This commit is contained in:
Alvaro Herrera 2020-10-27 14:31:37 -03:00
parent f893e68d76
commit 403a3d91c8
No known key found for this signature in database
GPG Key ID: 1C20ACB9D5C564AE
4 changed files with 78 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/bin/pg_dump/pg_backup.h
View File

@ -198,6 +198,8 @@ typedef struct Archive
int minRemoteVersion; /* allowable range */
int maxRemoteVersion;
bool hasGenericLockTable; /* can LOCK TABLE do non-table rels */
int numWorkers; /* number of parallel processes */
char *sync_snapshot_id; /* sync snapshot id for parallel operation */

64
src/bin/pg_dump/pg_backup_db.c
View File

@ -531,6 +531,70 @@ EndDBCopyMode(Archive *AHX, const char *tocEntryTag)
}
}
/*
* Does LOCK TABLE work on non-table relations on this server?
*
* Note: assumes it is called out of any transaction
*/
bool
IsLockTableGeneric(Archive *AHX)
{
ArchiveHandle *AH = (ArchiveHandle *) AHX;
PGresult *res;
char *sqlstate;
bool retval;
if (AHX->remoteVersion >= 140000)
return true;
else if (AHX->remoteVersion < 90500)
return false;
StartTransaction(AHX);
/*
* Try a LOCK TABLE on a well-known non-table catalog; WRONG_OBJECT_TYPE
* tells us that this server doesn't support locking non-table rels, while
* LOCK_NOT_AVAILABLE and INSUFFICIENT_PRIVILEGE tell us that it does.
* Report anything else as a fatal problem.
*/
#define ERRCODE_INSUFFICIENT_PRIVILEGE "42501"
#define ERRCODE_WRONG_OBJECT_TYPE "42809"
#define ERRCODE_LOCK_NOT_AVAILABLE "55P03"
res = PQexec(AH->connection,
"LOCK TABLE pg_catalog.pg_class_tblspc_relfilenode_index IN ACCESS SHARE MODE NOWAIT");
switch (PQresultStatus(res))
{
case PGRES_COMMAND_OK:
retval = true;
break;
case PGRES_FATAL_ERROR:
sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
if (strcmp(sqlstate, ERRCODE_WRONG_OBJECT_TYPE) == 0)
{
retval = false;
break;
}
else if (strcmp(sqlstate, ERRCODE_LOCK_NOT_AVAILABLE) == 0 ||
strcmp(sqlstate, ERRCODE_INSUFFICIENT_PRIVILEGE) == 0)
{
retval = true;
break;
}
/* else, falls through */
default:
warn_or_exit_horribly(AH, "LOCK TABLE failed for \"%s\": %s",
"pg_catalog.pg_class_tblspc_relfilenode_index",
PQerrorMessage(AH->connection));
retval = false; /* not reached */
break;
}
PQclear(res);
CommitTransaction(AHX);
return retval;
}
void
StartTransaction(Archive *AHX)
{

2
src/bin/pg_dump/pg_backup_db.h
View File

@ -20,6 +20,8 @@ extern PGresult *ExecuteSqlQueryForSingleRow(Archive *fout, const char *query);
extern void EndDBCopyMode(Archive *AHX, const char *tocEntryTag);
extern bool IsLockTableGeneric(Archive *AHX);
extern void StartTransaction(Archive *AHX);
extern void CommitTransaction(Archive *AHX);

17
src/bin/pg_dump/pg_dump.c
View File

@ -1176,6 +1176,9 @@ setup_connection(Archive *AH, const char *dumpencoding,
ExecuteSqlStatement(AH, "SET row_security = off");
}
/* Detect whether LOCK TABLE can handle non-table relations */
AH->hasGenericLockTable = IsLockTableGeneric(AH);
/*
* Start transaction-snapshot mode transaction to dump consistent data.
*/
@ -6843,16 +6846,16 @@ getTables(Archive *fout, int *numTables)
* assume our lock on the child is enough to prevent schema
* alterations to parent tables.
*
* NOTE: it'd be kinda nice to lock other relations too, not only
* plain or partitioned tables, but the backend doesn't presently
* allow that.
*
* We only need to lock the table for certain components; see
* We only need to lock the relation for certain components; see
* pg_dump.h
*
* On server versions that support it, we lock all relations not just
* plain tables.
*/
if (tblinfo[i].dobj.dump &&
(tblinfo[i].relkind == RELKIND_RELATION ||
tblinfo->relkind == RELKIND_PARTITIONED_TABLE) &&
(fout->hasGenericLockTable ||
tblinfo[i].relkind == RELKIND_PARTITIONED_TABLE ||
tblinfo[i].relkind == RELKIND_RELATION) &&
(tblinfo[i].dobj.dump & DUMP_COMPONENTS_REQUIRING_LOCK))
{
resetPQExpBuffer(query);