While debugging an out-of-memory situation, I noticed that the relcache
entry of each index consumes 2k of memory. From a memory dump:
...
pg_database_datname_index: 2048 total in 1 blocks; 712 free (0 chunks);
1336 used
pg_trigger_tgrelid_tgname_index: 2048 total in 1 blocks; 576 free (0
chunks); 1472 used
pg_rewrite_rel_rulename_index: 2048 total in 1 blocks; 576 free (0 chunks);
1472 used
pg_amproc_fam_proc_index: 2048 total in 1 blocks; 232 free (0 chunks); 1816
used
pg_opclass_oid_index: 2048 total in 1 blocks; 664 free (0 chunks); 1384 used
pg_index_indexrelid_index: 2048 total in 1 blocks; 664 free (0 chunks);
1384 used
pg_attribute_relid_attnum_index: 2048 total in 1 blocks; 528 free (0
chunks); 1520 used
pg_class_oid_index: 2048 total in 1 blocks; 664 free (0 chunks); 1384 used
Looking closer at where that memory is spent, a lot of it goes into the
FmgrInfo structs in RelationAmInfo. But some of them are outright unused
(ambuild, ambuildempty, amcostestimate, amoptions), and a few others
hardly are called so seldom that they hardly need to be cached
(ambuildelete, ambacuumcleanup). Removing those fields, patch attached,
reduces the memory usage nicely:
...
pg_database_datname_index: 1024 total in 1 blocks; 200 free (0 chunks); 824
used
pg_trigger_tgrelid_tgname_index: 1024 total in 1 blocks; 64 free (0
chunks); 960 used
pg_rewrite_rel_rulename_index: 1024 total in 1 blocks; 64 free (0 chunks);
960 used
pg_amproc_fam_proc_index: 3072 total in 2 blocks; 1736 free (2 chunks);
1336 used
pg_opclass_oid_index: 1024 total in 1 blocks; 152 free (0 chunks); 872 used
pg_index_indexrelid_index: 1024 total in 1 blocks; 152 free (0 chunks); 872
used
pg_attribute_relid_attnum_index: 1024 total in 1 blocks; 16 free (0
chunks); 1008 used
pg_class_oid_index: 1024 total in 1 blocks; 152 free (0 chunks); 872 used
This brings most index entries from two 1k blocks down to one 1k block.
A backend seems to load about 60 indexes into the cache for system
tables, so that saves about ~60 kB of memory for every backend at a minimum.
This isn't a huge difference, unless you access a huge number of
indexes. But the patch is trivial, and every little helps. Any
objections if I commit this to master?
- Heikki
diff --git a/src/backend/access/index/indexam.c b/src/backend/access/index/indexam.c
index ce94649..b9e519a 100644
--- a/src/backend/access/index/indexam.c
+++ b/src/backend/access/index/indexam.c
@@ -671,14 +671,19 @@ index_bulk_delete(IndexVacuumInfo *info,
void *callback_state)
{
Relation indexRelation = info->index;
- FmgrInfo *procedure;
+ RegProcedure procOid;
+ FmgrInfo procedure;
IndexBulkDeleteResult *result;
RELATION_CHECKS;
- GET_REL_PROCEDURE(ambulkdelete);
+
+ procOid = indexRelation->rd_am->ambulkdelete;
+ if (!RegProcedureIsValid(procOid))
+ elog(ERROR, "invalid ambulkdelete regproc");
+ fmgr_info(procOid, &procedure);
result = (IndexBulkDeleteResult *)
- DatumGetPointer(FunctionCall4(procedure,
+ DatumGetPointer(FunctionCall4(&procedure,
PointerGetDatum(info),
PointerGetDatum(stats),
PointerGetDatum((Pointer) callback),
@@ -698,14 +703,19 @@ index_vacuum_cleanup(IndexVacuumInfo *info,
IndexBulkDeleteResult *stats)
{
Relation indexRelation = info->index;
- FmgrInfo *procedure;
+ RegProcedure procOid;
+ FmgrInfo procedure;
IndexBulkDeleteResult *result;
RELATION_CHECKS;
- GET_REL_PROCEDURE(amvacuumcleanup);
+
+ procOid = indexRelation->rd_am->amvacuumcleanup;
+ if (!RegProcedureIsValid(procOid))
+ elog(ERROR, "invalid amvacuumcleanup regproc");
+ fmgr_info(procOid, &procedure);
result = (IndexBulkDeleteResult *)
- DatumGetPointer(FunctionCall2(procedure,
+ DatumGetPointer(FunctionCall2(&procedure,
PointerGetDatum(info),
PointerGetDatum(stats)));
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index a4daf77..05f2011 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -47,8 +47,8 @@ typedef LockInfoData *LockInfo;
/*
- * Cached lookup information for the index access method functions defined
- * by the pg_am row associated with an index relation.
+ * Cached lookup information for the frequently used index access method
+ * functions, defined by the pg_am row associated with an index relation.
*/
typedef struct RelationAmInfo
{
@@ -60,13 +60,7 @@ typedef struct RelationAmInfo
FmgrInfo amendscan;
FmgrInfo ammarkpos;
FmgrInfo amrestrpos;
- FmgrInfo ambuild;
- FmgrInfo ambuildempty;
- FmgrInfo ambulkdelete;
- FmgrInfo amvacuumcleanup;
FmgrInfo amcanreturn;
- FmgrInfo amcostestimate;
- FmgrInfo amoptions;
} RelationAmInfo;
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