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Prevent synchronous scan during GIN index build, because GIN is optimized

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for inserting tuples in increasing TID order.  It's not clear whether this
fully explains Ivan Sergio Borgonovo's complaint, but simple testing
confirms that a scan that doesn't start at block 0 can slow GIN build by
a factor of three or four.

Backpatch to 8.3.  Sync scan didn't exist before that.
This commit is contained in:
Tom Lane
2008-11-13 17:42:10 +00:00
parent 3379fae6de
commit 10e3acb8e7
6 changed files with 22 additions and 12 deletions
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9
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 1.15 2008/09/30 10:52:10 heikki Exp $
* $PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.16 2008/11/13 17:42:09 tgl Exp $
*-------------------------------------------------------------------------
*/
@ -340,8 +340,11 @@ ginbuild(PG_FUNCTION_ARGS)
buildstate.accum.ginstate = &buildstate.ginstate;
ginInitBA(&buildstate.accum);
/* do the heap scan */
reltuples = IndexBuildHeapScan(heap, index, indexInfo,
/*
* Do the heap scan. We disallow sync scan here because dataPlaceToPage
* prefers to receive tuples in TID order.
*/
reltuples = IndexBuildHeapScan(heap, index, indexInfo, false,
ginBuildCallback, (void *) &buildstate);
/* dump remaining entries to the index */