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Install a search tree depth limit in GIN bulk-insert operations, to prevent

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them from degrading badly when the input is sorted or nearly so.  In this
scenario the tree is unbalanced to the point of becoming a mere linked list,
so insertions become O(N^2).  The easiest and most safely back-patchable
solution is to stop growing the tree sooner, ie limit the growth of N.  We
might later consider a rebalancing tree algorithm, but it's not clear that
the benefit would be worth the cost and complexity.  Per report from Sergey
Burladyan and an earlier complaint from Heikki.

Back-patch to 8.2; older versions didn't have GIN indexes.
This commit is contained in:
Tom Lane 2009-03-24 22:06:03 +00:00
parent fc022d72c7
commit e5efda442c
3 changed files with 20 additions and 12 deletions
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9
src/backend/access/gin/ginfast.c
View File

@ -11,7 +11,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gin/ginfast.c,v 1.1 2009/03/24 20:17:10 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/gin/ginfast.c,v 1.2 2009/03/24 22:06:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -749,9 +749,10 @@ ginInsertCleanup(Relation index, GinState *ginstate,
* XXX using up maintenance_work_mem here is probably unreasonably
* much, since vacuum might already be using that much.
*/
if ( GinPageGetOpaque(page)->rightlink == InvalidBlockNumber ||
( GinPageHasFullRow(page) &&
accum.allocatedMemory > maintenance_work_mem * 1024L ) )
if (GinPageGetOpaque(page)->rightlink == InvalidBlockNumber ||
(GinPageHasFullRow(page) &&
(accum.allocatedMemory >= maintenance_work_mem * 1024L ||
accum.maxdepth > GIN_MAX_TREE_DEPTH)))
{
ItemPointerData *list;
uint32 nlist;

6
src/backend/access/gin/gininsert.c
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.19 2009/03/24 20:17:11 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.20 2009/03/24 22:06:03 tgl Exp $
*-------------------------------------------------------------------------
*/
@ -245,7 +245,9 @@ ginBuildCallback(Relation index, HeapTuple htup, Datum *values,
&htup->t_self);
/* If we've maxed out our available memory, dump everything to the index */
if (buildstate->accum.allocatedMemory >= maintenance_work_mem * 1024L)
/* Also dump if the tree seems to be getting too unbalanced */
if (buildstate->accum.allocatedMemory >= maintenance_work_mem * 1024L ||
buildstate->accum.maxdepth > GIN_MAX_TREE_DEPTH)
{
ItemPointerData *list;
Datum entry;

17
src/include/access/gin.h
View File

@ -4,7 +4,7 @@
*
* Copyright (c) 2006-2009, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/include/access/gin.h,v 1.29 2009/03/24 20:17:14 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/gin.h,v 1.30 2009/03/24 22:06:03 tgl Exp $
*--------------------------------------------------------------------------
*/
#ifndef GIN_H
@ -26,6 +26,14 @@
#define GIN_COMPARE_PARTIAL_PROC 5
#define GINNProcs 5
/*
* Max depth allowed in search tree during bulk inserts. This is to keep from
* degenerating to O(N^2) behavior when the tree is unbalanced due to sorted
* or nearly-sorted input. (Perhaps it would be better to use a balanced-tree
* algorithm, but in common cases that would only add useless overhead.)
*/
#define GIN_MAX_TREE_DEPTH 100
/*
* Page opaque data in a inverted index page.
*
@ -434,12 +442,9 @@ extern IndexTuple ginPageGetLinkItup(Buffer buf);
/* gindatapage.c */
extern int compareItemPointers(ItemPointer a, ItemPointer b);
extern void
MergeItemPointers(
ItemPointerData *dst,
extern void MergeItemPointers(ItemPointerData *dst,
ItemPointerData *a, uint32 na,
ItemPointerData *b, uint32 nb
);
ItemPointerData *b, uint32 nb);
extern void GinDataPageAddItem(Page page, void *data, OffsetNumber offset);
extern void PageDeletePostingItem(Page page, OffsetNumber offset);