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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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6
src/backend/access/gin/gininsert.c
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@ -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;