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Postgres FD Implementation
Commit 540e69a0 authored by Tom Lane's avatar Tom Lane
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Add an index on pg_inherits.inhparent, and use it to avoid seqscans in 

find_inheritance_children().  This is a complete no-op in databases without
any inheritance.  In databases where there are just a few entries in
pg_inherits, it could conceivably be a small loss.  However, in databases with
many inheritance parents, it can be a big win.
parent 649b5ec7
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Showing with 82 additions and 27 deletions
src/backend/catalog/pg_inherits.c
View file @ 540e69a0
......@@ -13,13 +13,15 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/catalog/pg_inherits.c,v 1.3 2009/06/11 14:48:55 momjian Exp $
* $PostgreSQL: pgsql/src/backend/catalog/pg_inherits.c,v 1.4 2009/12/29 22:00:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/indexing.h"
#include "catalog/pg_class.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_inherits_fn.h"
......@@ -29,6 +31,8 @@
#include "utils/syscache.h"
#include "utils/tqual.h"
static int oid_cmp(const void *p1, const void *p2);
/*
* find_inheritance_children
......@@ -46,10 +50,14 @@ find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
{
List *list = NIL;
Relation relation;
HeapScanDesc scan;
SysScanDesc scan;
ScanKeyData key[1];
HeapTuple inheritsTuple;
Oid inhrelid;
Oid *oidarr;
int maxoids,
numoids,
i;
/*
* Can skip the scan if pg_class shows the relation has never had a
......@@ -59,21 +67,52 @@ find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
return NIL;
/*
* XXX might be a good idea to create an index on pg_inherits' inhparent
* field, so that we can use an indexscan instead of sequential scan here.
* However, in typical databases pg_inherits won't have enough entries to
* justify an indexscan...
* Scan pg_inherits and build a working array of subclass OIDs.
*/
maxoids = 32;
oidarr = (Oid *) palloc(maxoids * sizeof(Oid));
numoids = 0;
relation = heap_open(InheritsRelationId, AccessShareLock);
ScanKeyInit(&key[0],
Anum_pg_inherits_inhparent,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(parentrelId));
scan = heap_beginscan(relation, SnapshotNow, 1, key);
while ((inheritsTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
scan = systable_beginscan(relation, InheritsParentIndexId, true,
SnapshotNow, 1, key);
while ((inheritsTuple = systable_getnext(scan)) != NULL)
{
inhrelid = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhrelid;
if (numoids >= maxoids)
{
maxoids *= 2;
oidarr = (Oid *) repalloc(oidarr, maxoids * sizeof(Oid));
}
oidarr[numoids++] = inhrelid;
}
systable_endscan(scan);
heap_close(relation, AccessShareLock);
/*
* If we found more than one child, sort them by OID. This ensures
* reasonably consistent behavior regardless of the vagaries of an
* indexscan. This is important since we need to be sure all backends
* lock children in the same order to avoid needless deadlocks.
*/
if (numoids > 1)
qsort(oidarr, numoids, sizeof(Oid), oid_cmp);
/*
* Acquire locks and build the result list.
*/
for (i = 0; i < numoids; i++)
{
inhrelid = oidarr[i];
if (lockmode != NoLock)
{
......@@ -99,8 +138,7 @@ find_inheritance_children(Oid parentrelId, LOCKMODE lockmode)
list = lappend_oid(list, inhrelid);
}
heap_endscan(scan);
heap_close(relation, AccessShareLock);
pfree(oidarr);
return list;
}
......@@ -231,7 +269,7 @@ typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId)
{
Oid this_relid = lfirst_oid(queue_item);
ScanKeyData skey;
HeapScanDesc inhscan;
SysScanDesc inhscan;
HeapTuple inhtup;
/*
......@@ -255,9 +293,10 @@ typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId)
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(this_relid));
inhscan = heap_beginscan(inhrel, SnapshotNow, 1, &skey);
inhscan = systable_beginscan(inhrel, InheritsRelidSeqnoIndexId, true,
SnapshotNow, 1, &skey);
while ((inhtup = heap_getnext(inhscan, ForwardScanDirection)) != NULL)
while ((inhtup = systable_getnext(inhscan)) != NULL)
{
Form_pg_inherits inh = (Form_pg_inherits) GETSTRUCT(inhtup);
Oid inhparent = inh->inhparent;
......@@ -273,7 +312,7 @@ typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId)
queue = lappend_oid(queue, inhparent);
}
heap_endscan(inhscan);
systable_endscan(inhscan);
if (result)
break;
......@@ -287,3 +326,18 @@ typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId)
return result;
}
/* qsort comparison function */
static int
oid_cmp(const void *p1, const void *p2)
{
Oid v1 = *((const Oid *) p1);
Oid v2 = *((const Oid *) p2);
if (v1 < v2)
return -1;
if (v1 > v2)
return 1;
return 0;
}
src/backend/commands/tablecmds.c
View file @ 540e69a0
......@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.311 2009/12/23 16:43:43 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.312 2009/12/29 22:00:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -1793,8 +1793,8 @@ StoreCatalogInheritance1(Oid relationId, Oid parentOid,
int16 seqNumber, Relation inhRelation)
{
TupleDesc desc = RelationGetDescr(inhRelation);
Datum datum[Natts_pg_inherits];
bool nullarr[Natts_pg_inherits];
Datum values[Natts_pg_inherits];
bool nulls[Natts_pg_inherits];
ObjectAddress childobject,
parentobject;
HeapTuple tuple;
......@@ -1802,15 +1802,13 @@ StoreCatalogInheritance1(Oid relationId, Oid parentOid,
/*
* Make the pg_inherits entry
*/
datum[0] = ObjectIdGetDatum(relationId); /* inhrelid */
datum[1] = ObjectIdGetDatum(parentOid); /* inhparent */
datum[2] = Int16GetDatum(seqNumber); /* inhseqno */
values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(relationId);
values[Anum_pg_inherits_inhparent - 1] = ObjectIdGetDatum(parentOid);
values[Anum_pg_inherits_inhseqno - 1] = Int16GetDatum(seqNumber);
nullarr[0] = false;
nullarr[1] = false;
nullarr[2] = false;
memset(nulls, 0, sizeof(nulls));
tuple = heap_form_tuple(desc, datum, nullarr);
tuple = heap_form_tuple(desc, values, nulls);
simple_heap_insert(inhRelation, tuple);
......
src/include/catalog/catversion.h
View file @ 540e69a0
......@@ -37,7 +37,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.562 2009/12/29 20:11:45 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.563 2009/12/29 22:00:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 200912281
#define CATALOG_VERSION_NO 200912291
#endif
src/include/catalog/indexing.h
View file @ 540e69a0
......@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/catalog/indexing.h,v 1.112 2009/12/29 20:11:45 tgl Exp $
* $PostgreSQL: pgsql/src/include/catalog/indexing.h,v 1.113 2009/12/29 22:00:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -156,6 +156,9 @@ DECLARE_UNIQUE_INDEX(pg_index_indexrelid_index, 2679, on pg_index using btree(in
DECLARE_UNIQUE_INDEX(pg_inherits_relid_seqno_index, 2680, on pg_inherits using btree(inhrelid oid_ops, inhseqno int4_ops));
#define InheritsRelidSeqnoIndexId 2680
/* This following index is not used for a cache and is not unique */
DECLARE_INDEX(pg_inherits_parent_index, 2187, on pg_inherits using btree(inhparent oid_ops));
#define InheritsParentIndexId 2187
DECLARE_UNIQUE_INDEX(pg_language_name_index, 2681, on pg_language using btree(lanname name_ops));
#define LanguageNameIndexId 2681
......
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