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Arrange for large sequential scans to synchronize with each other, so that

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when multiple backends are scanning the same relation concurrently, each page
is (ideally) read only once.

Jeff Davis, with review by Heikki and Tom.
This commit is contained in:
Tom Lane
2007-06-08 18:23:53 +00:00
parent 6d6d14b6d5
commit a04a423599
10 changed files with 485 additions and 31 deletions
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18
src/backend/utils/misc/guc.c
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@ -10,7 +10,7 @@
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.395 2007/06/05 21:50:19 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.396 2007/06/08 18:23:52 tgl Exp $
*
*--------------------------------------------------------------------
*/
@ -109,6 +109,9 @@ extern bool fullPageWrites;
#ifdef TRACE_SORT
extern bool trace_sort;
#endif
#ifdef TRACE_SYNCSCAN
extern bool trace_syncscan;
#endif
#ifdef DEBUG_BOUNDED_SORT
extern bool optimize_bounded_sort;
#endif
@ -970,6 +973,19 @@ static struct config_bool ConfigureNamesBool[] =
},
#endif
#ifdef TRACE_SYNCSCAN
/* this is undocumented because not exposed in a standard build */
{
{"trace_syncscan", PGC_USERSET, DEVELOPER_OPTIONS,
gettext_noop("Generate debugging output for synchronized scanning."),
NULL,
GUC_NOT_IN_SAMPLE
},
&trace_syncscan,
false, NULL, NULL
},
#endif
#ifdef DEBUG_BOUNDED_SORT
/* this is undocumented because not exposed in a standard build */
{