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Create a syscache for pg_database-indexed-by-oid, and make use of it

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in various places that were previously doing ad hoc pg_database searches.
This may speed up database-related privilege checks a little bit, but
the main motivation is to eliminate the performance reason for having
ReverifyMyDatabase do such a lot of stuff (viz, avoiding repeat scans
of pg_database during backend startup).  The locking reason for having
that routine is about to go away, and it'd be good to have the option
to break it up.
This commit is contained in:
Tom Lane
2006-05-03 22:45:26 +00:00
parent 5320c6cf6b
commit cb98e6fb8f
8 changed files with 116 additions and 205 deletions
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59
src/backend/commands/dbcommands.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.179 2006/03/29 21:17:38 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.180 2006/05/03 22:45:26 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -556,8 +556,6 @@ dropdb(const char *dbname, bool missing_ok)
Oid db_id;
bool db_istemplate;
Relation pgdbrel;
SysScanDesc pgdbscan;
ScanKeyData key;
HeapTuple tup;
PreventTransactionChain((void *) dbname, "DROP DATABASE");
@ -629,31 +627,17 @@ dropdb(const char *dbname, bool missing_ok)
dbname)));
/*
* Find the database's tuple by OID (should be unique).
* Remove the database's tuple from pg_database.
*/
ScanKeyInit(&key,
ObjectIdAttributeNumber,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(db_id));
pgdbscan = systable_beginscan(pgdbrel, DatabaseOidIndexId, true,
SnapshotNow, 1, &key);
tup = systable_getnext(pgdbscan);
tup = SearchSysCache(DATABASEOID,
ObjectIdGetDatum(db_id),
0, 0, 0);
if (!HeapTupleIsValid(tup))
{
/*
* This error should never come up since the existence of the database
* is checked earlier
*/
elog(ERROR, "database \"%s\" doesn't exist despite earlier reports to the contrary",
dbname);
}
elog(ERROR, "cache lookup failed for database %u", db_id);
/* Remove the database's tuple from pg_database */
simple_heap_delete(pgdbrel, &tup->t_self);
systable_endscan(pgdbscan);
ReleaseSysCache(tup);
/*
* Delete any comments associated with the database
@ -1262,7 +1246,10 @@ get_database_oid(const char *dbname)
HeapTuple dbtuple;
Oid oid;
/* There's no syscache for pg_database, so must look the hard way */
/*
* There's no syscache for pg_database indexed by name,
* so we must look the hard way.
*/
pg_database = heap_open(DatabaseRelationId, AccessShareLock);
ScanKeyInit(&entry[0],
Anum_pg_database_datname,
@ -1296,32 +1283,20 @@ get_database_oid(const char *dbname)
char *
get_database_name(Oid dbid)
{
Relation pg_database;
ScanKeyData entry[1];
SysScanDesc scan;
HeapTuple dbtuple;
char *result;
/* There's no syscache for pg_database, so must look the hard way */
pg_database = heap_open(DatabaseRelationId, AccessShareLock);
ScanKeyInit(&entry[0],
ObjectIdAttributeNumber,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(dbid));
scan = systable_beginscan(pg_database, DatabaseOidIndexId, true,
SnapshotNow, 1, entry);
dbtuple = systable_getnext(scan);
/* We assume that there can be at most one matching tuple */
dbtuple = SearchSysCache(DATABASEOID,
ObjectIdGetDatum(dbid),
0, 0, 0);
if (HeapTupleIsValid(dbtuple))
{
result = pstrdup(NameStr(((Form_pg_database) GETSTRUCT(dbtuple))->datname));
ReleaseSysCache(dbtuple);
}
else
result = NULL;
systable_endscan(scan);
heap_close(pg_database, AccessShareLock);
return result;
}