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Reduce the acceptable staleness of pgstat data for autovacuum, per the

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longstanding note in the source that this patch removes.
This commit is contained in:
Alvaro Herrera 2008-11-03 19:03:41 +00:00
parent b8fab2411d
commit 88dd4b0a0d
2 changed files with 16 additions and 7 deletions
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8
src/backend/postmaster/autovacuum.c
View File

@ -55,7 +55,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.85 2008/11/02 21:24:52 tgl Exp $ * $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.86 2008/11/03 19:03:41 alvherre Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -2149,8 +2149,10 @@ do_autovacuum(void)
* It could have changed if something else processed the table while * It could have changed if something else processed the table while
* we weren't looking. * we weren't looking.
* *
* FIXME we ignore the possibility that the table was finished being * Note: we have a special case in pgstat code to ensure that the stats
* vacuumed in the last 500ms (PGSTAT_STAT_INTERVAL). This is a bug. * we read are as up-to-date as possible, to avoid the problem that
* somebody just finished vacuuming this table. The window to the race
* condition is not closed but it is very small.
*/ */
MemoryContextSwitchTo(AutovacMemCxt); MemoryContextSwitchTo(AutovacMemCxt);
tab = table_recheck_autovac(relid, table_toast_map); tab = table_recheck_autovac(relid, table_toast_map);

15
src/backend/postmaster/pgstat.c
View File

@ -13,7 +13,7 @@
* *
* Copyright (c) 2001-2008, PostgreSQL Global Development Group * Copyright (c) 2001-2008, PostgreSQL Global Development Group
* *
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.182 2008/11/03 01:17:08 tgl Exp $ * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.183 2008/11/03 19:03:41 alvherre Exp $
* ---------- * ----------
*/ */
#include "postgres.h" #include "postgres.h"
@ -3381,7 +3381,10 @@ backend_read_statsfile(void)
/* /*
* We set the minimum acceptable timestamp to PGSTAT_STAT_INTERVAL msec * We set the minimum acceptable timestamp to PGSTAT_STAT_INTERVAL msec
* before now. This indirectly ensures that the collector needn't write * before now. This indirectly ensures that the collector needn't write
* the file more often than PGSTAT_STAT_INTERVAL. * the file more often than PGSTAT_STAT_INTERVAL. In an autovacuum
* worker, however, we want a lower delay to avoid using stale data, so we
* use PGSTAT_RETRY_DELAY (since the number of worker is low, this
* shouldn't be a problem).
* *
* Note that we don't recompute min_ts after sleeping; so we might end up * Note that we don't recompute min_ts after sleeping; so we might end up
* accepting a file a bit older than PGSTAT_STAT_INTERVAL. In practice * accepting a file a bit older than PGSTAT_STAT_INTERVAL. In practice
@ -3389,8 +3392,12 @@ backend_read_statsfile(void)
* PGSTAT_STAT_INTERVAL; and we don't want to lie to the collector about * PGSTAT_STAT_INTERVAL; and we don't want to lie to the collector about
* what our cutoff time really is. * what our cutoff time really is.
*/ */
min_ts = TimestampTzPlusMilliseconds(GetCurrentTimestamp(), if (IsAutoVacuumWorkerProcess())
-PGSTAT_STAT_INTERVAL); min_ts = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
-PGSTAT_RETRY_DELAY);
else
min_ts = TimestampTzPlusMilliseconds(GetCurrentTimestamp(),
-PGSTAT_STAT_INTERVAL);
/* /*
* Loop until fresh enough stats file is available or we ran out of time. * Loop until fresh enough stats file is available or we ran out of time.