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Commite5efda4

Browse files
committed
Install a search tree depth limit in GIN bulk-insert operations, to prevent
them from degrading badly when the input is sorted or nearly so. In thisscenario 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-patchablesolution is to stop growing the tree sooner, ie limit the growth of N. Wemight later consider a rebalancing tree algorithm, but it's not clear thatthe benefit would be worth the cost and complexity. Per report from SergeyBurladyan and an earlier complaint from Heikki.Back-patch to 8.2; older versions didn't have GIN indexes.
1 parentfc022d7 commite5efda4

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3 files changed

+20
-12
lines changed

3 files changed

+20
-12
lines changed

‎src/backend/access/gin/ginfast.c

Lines changed: 5 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
* Portions Copyright (c) 1994, Regents of the University of California
1212
*
1313
* IDENTIFICATION
14-
*$PostgreSQL: pgsql/src/backend/access/gin/ginfast.c,v 1.1 2009/03/2420:17:10 tgl Exp $
14+
*$PostgreSQL: pgsql/src/backend/access/gin/ginfast.c,v 1.2 2009/03/2422:06:03 tgl Exp $
1515
*
1616
*-------------------------------------------------------------------------
1717
*/
@@ -749,9 +749,10 @@ ginInsertCleanup(Relation index, GinState *ginstate,
749749
* XXX using up maintenance_work_mem here is probably unreasonably
750750
* much, since vacuum might already be using that much.
751751
*/
752-
if (GinPageGetOpaque(page)->rightlink==InvalidBlockNumber||
753-
(GinPageHasFullRow(page)&&
754-
accum.allocatedMemory>maintenance_work_mem*1024L ) )
752+
if (GinPageGetOpaque(page)->rightlink==InvalidBlockNumber||
753+
(GinPageHasFullRow(page)&&
754+
(accum.allocatedMemory >=maintenance_work_mem*1024L||
755+
accum.maxdepth>GIN_MAX_TREE_DEPTH)))
755756
{
756757
ItemPointerData*list;
757758
uint32nlist;

‎src/backend/access/gin/gininsert.c

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
*$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.19 2009/03/2420:17:11 tgl Exp $
11+
*$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.20 2009/03/2422:06:03 tgl Exp $
1212
*-------------------------------------------------------------------------
1313
*/
1414

@@ -245,7 +245,9 @@ ginBuildCallback(Relation index, HeapTuple htup, Datum *values,
245245
&htup->t_self);
246246

247247
/* If we've maxed out our available memory, dump everything to the index */
248-
if (buildstate->accum.allocatedMemory >=maintenance_work_mem*1024L)
248+
/* Also dump if the tree seems to be getting too unbalanced */
249+
if (buildstate->accum.allocatedMemory >=maintenance_work_mem*1024L||
250+
buildstate->accum.maxdepth>GIN_MAX_TREE_DEPTH)
249251
{
250252
ItemPointerData*list;
251253
Datumentry;

‎src/include/access/gin.h

Lines changed: 11 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
*
55
*Copyright (c) 2006-2009, PostgreSQL Global Development Group
66
*
7-
*$PostgreSQL: pgsql/src/include/access/gin.h,v 1.29 2009/03/2420:17:14 tgl Exp $
7+
*$PostgreSQL: pgsql/src/include/access/gin.h,v 1.30 2009/03/2422:06:03 tgl Exp $
88
*--------------------------------------------------------------------------
99
*/
1010
#ifndefGIN_H
@@ -26,6 +26,14 @@
2626
#defineGIN_COMPARE_PARTIAL_PROC 5
2727
#defineGINNProcs 5
2828

29+
/*
30+
* Max depth allowed in search tree during bulk inserts. This is to keep from
31+
* degenerating to O(N^2) behavior when the tree is unbalanced due to sorted
32+
* or nearly-sorted input. (Perhaps it would be better to use a balanced-tree
33+
* algorithm, but in common cases that would only add useless overhead.)
34+
*/
35+
#defineGIN_MAX_TREE_DEPTH 100
36+
2937
/*
3038
* Page opaque data in a inverted index page.
3139
*
@@ -434,12 +442,9 @@ extern IndexTuple ginPageGetLinkItup(Buffer buf);
434442

435443
/* gindatapage.c */
436444
externintcompareItemPointers(ItemPointera,ItemPointerb);
437-
externvoid
438-
MergeItemPointers(
439-
ItemPointerData*dst,
445+
externvoidMergeItemPointers(ItemPointerData*dst,
440446
ItemPointerData*a,uint32na,
441-
ItemPointerData*b,uint32nb
442-
);
447+
ItemPointerData*b,uint32nb);
443448

444449
externvoidGinDataPageAddItem(Pagepage,void*data,OffsetNumberoffset);
445450
externvoidPageDeletePostingItem(Pagepage,OffsetNumberoffset);

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