From b2a2f4cef7e180735ab9e80cea3a0f73cd4edc58 Mon Sep 17 00:00:00 2001 From: Tom Lane <tgl@sss.pgh.pa.us> Date: Thu, 18 Nov 2004 01:14:26 +0000 Subject: [PATCH] Force pg_database updates out to disk immediately after ALTER DATABASE; this is to avoid scenarios where incoming backends find no live copies of a database's row because the only live copy is in an as-yet-unwritten shared buffer, which they can't see. Also, use FlushRelationBuffers() for forcing out pg_database, instead of the much more expensive BufferSync(). There's no need to write out pages belonging to other relations. --- src/backend/commands/dbcommands.c | 66 ++++++++++++++++++++++--------- 1 file changed, 47 insertions(+), 19 deletions(-) diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index a74ad9b2f07..6d0fa6a13d4 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -9,7 +9,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.146 2004/10/28 00:39:58 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.147 2004/11/18 01:14:26 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -330,7 +330,7 @@ createdb(const CreatedbStmt *stmt) /* * Force dirty buffers out to disk, to ensure source database is * up-to-date for the copy. (We really only need to flush buffers for - * the source database...) + * the source database, but bufmgr.c provides no API for that.) */ BufferSync(-1, -1); @@ -497,15 +497,15 @@ createdb(const CreatedbStmt *stmt) /* Update indexes */ CatalogUpdateIndexes(pg_database_rel, tuple); - /* Close pg_database, but keep lock till commit */ - heap_close(pg_database_rel, NoLock); - /* * Force dirty buffers out to disk, so that newly-connecting backends * will see the new database in pg_database right away. (They'll see * an uncommitted tuple, but they don't care; see GetRawDatabaseInfo.) */ - BufferSync(-1, -1); + FlushRelationBuffers(pg_database_rel, MaxBlockNumber); + + /* Close pg_database, but keep exclusive lock till commit */ + heap_close(pg_database_rel, NoLock); } @@ -607,12 +607,6 @@ dropdb(const char *dbname) */ DeleteComments(db_id, RelationGetRelid(pgdbrel), 0); - /* - * Close pg_database, but keep exclusive lock till commit to ensure - * that any new backend scanning pg_database will see the tuple dead. - */ - heap_close(pgdbrel, NoLock); - /* * Drop pages for this database that are in the shared buffer cache. * This is important to ensure that no remaining backend tries to @@ -644,7 +638,10 @@ dropdb(const char *dbname) * (They'll see an uncommitted deletion, but they don't care; see * GetRawDatabaseInfo.) */ - BufferSync(-1, -1); + FlushRelationBuffers(pgdbrel, MaxBlockNumber); + + /* Close pg_database, but keep exclusive lock till commit */ + heap_close(pgdbrel, NoLock); } @@ -733,7 +730,6 @@ RenameDatabase(const char *oldname, const char *newname) CatalogUpdateIndexes(rel, newtup); systable_endscan(scan); - heap_close(rel, NoLock); /* * Force dirty buffers out to disk, so that newly-connecting backends @@ -741,7 +737,10 @@ RenameDatabase(const char *oldname, const char *newname) * see an uncommitted tuple, but they don't care; see * GetRawDatabaseInfo.) */ - BufferSync(-1, -1); + FlushRelationBuffers(rel, MaxBlockNumber); + + /* Close pg_database, but keep exclusive lock till commit */ + heap_close(rel, NoLock); } @@ -763,7 +762,10 @@ AlterDatabaseSet(AlterDatabaseSetStmt *stmt) valuestr = flatten_set_variable_args(stmt->variable, stmt->value); - rel = heap_openr(DatabaseRelationName, RowExclusiveLock); + /* + * We need AccessExclusiveLock so we can safely do FlushRelationBuffers. + */ + rel = heap_openr(DatabaseRelationName, AccessExclusiveLock); ScanKeyInit(&scankey, Anum_pg_database_datname, BTEqualStrategyNumber, F_NAMEEQ, @@ -821,6 +823,16 @@ AlterDatabaseSet(AlterDatabaseSetStmt *stmt) CatalogUpdateIndexes(rel, newtuple); systable_endscan(scan); + + /* + * Force dirty buffers out to disk, so that newly-connecting backends + * will see the altered row in pg_database right away. (They'll + * see an uncommitted tuple, but they don't care; see + * GetRawDatabaseInfo.) + */ + FlushRelationBuffers(rel, MaxBlockNumber); + + /* Close pg_database, but keep exclusive lock till commit */ heap_close(rel, NoLock); } @@ -837,7 +849,10 @@ AlterDatabaseOwner(const char *dbname, AclId newOwnerSysId) SysScanDesc scan; Form_pg_database datForm; - rel = heap_openr(DatabaseRelationName, RowExclusiveLock); + /* + * We need AccessExclusiveLock so we can safely do FlushRelationBuffers. + */ + rel = heap_openr(DatabaseRelationName, AccessExclusiveLock); ScanKeyInit(&scankey, Anum_pg_database_datname, BTEqualStrategyNumber, F_NAMEEQ, @@ -901,9 +916,22 @@ AlterDatabaseOwner(const char *dbname, AclId newOwnerSysId) CatalogUpdateIndexes(rel, newtuple); heap_freetuple(newtuple); + + /* must release buffer pins before FlushRelationBuffers */ + systable_endscan(scan); + + /* + * Force dirty buffers out to disk, so that newly-connecting backends + * will see the altered row in pg_database right away. (They'll + * see an uncommitted tuple, but they don't care; see + * GetRawDatabaseInfo.) + */ + FlushRelationBuffers(rel, MaxBlockNumber); } + else + systable_endscan(scan); - systable_endscan(scan); + /* Close pg_database, but keep exclusive lock till commit */ heap_close(rel, NoLock); } @@ -1176,7 +1204,7 @@ dbase_redo(XLogRecPtr lsn, XLogRecord *record) /* * Force dirty buffers out to disk, to ensure source database is * up-to-date for the copy. (We really only need to flush buffers for - * the source database...) + * the source database, but bufmgr.c provides no API for that.) */ BufferSync(-1, -1); -- GitLab