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Improve the IndexVacuumInfo/IndexBulkDeleteResult API to allow somewhat sane

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behavior in cases where we don't know the heap tuple count accurately; in
particular partial vacuum, but this also makes the API a bit more useful
for ANALYZE.  This patch adds "estimated_count" flags to both structs so
that an approximate count can be flagged as such, and adjusts the logic
so that approximate counts are not used for updating pg_class.reltuples.

This fixes my previous complaint that VACUUM was putting ridiculous values
into pg_class.reltuples for indexes.  The actual impact of that bug is
limited, because the planner only pays attention to reltuples for an index
if the index is partial; which probably explains why beta testers hadn't
noticed a degradation in plan quality from it.  But it needs to be fixed.

The whole thing is a bit messy and should be redesigned in future, because
reltuples now has the potential to drift quite far away from reality when
a long period elapses with no non-partial vacuums.  But this is as good as
it's going to get for 8.4.
This commit is contained in:
Tom Lane 2009-06-06 22:13:52 +00:00
parent 4334695b30
commit 32ea236361
10 changed files with 81 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/backend/access/gin/ginvacuum.c
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gin/ginvacuum.c,v 1.28 2009/03/24 20:17:11 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/gin/ginvacuum.c,v 1.29 2009/06/06 22:13:50 tgl Exp $
*-------------------------------------------------------------------------
*/
@ -741,6 +741,7 @@ ginvacuumcleanup(PG_FUNCTION_ARGS)
* tell how many distinct heap entries are referenced by a GIN index.
*/
stats->num_index_tuples = info->num_heap_tuples;
stats->estimated_count = info->estimated_count;
/*
* If vacuum full, we already have exclusive lock on the index. Otherwise,

5
src/backend/access/gist/gistvacuum.c
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/gist/gistvacuum.c,v 1.43 2009/03/24 20:17:11 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/gist/gistvacuum.c,v 1.44 2009/06/06 22:13:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -524,8 +524,8 @@ gistvacuumcleanup(PG_FUNCTION_ARGS)
{
stats = (GistBulkDeleteResult *) palloc0(sizeof(GistBulkDeleteResult));
/* use heap's tuple count */
Assert(info->num_heap_tuples >= 0);
stats->std.num_index_tuples = info->num_heap_tuples;
stats->std.estimated_count = info->estimated_count;
/*
* XXX the above is wrong if index is partial. Would it be OK to just
@ -679,6 +679,7 @@ gistbulkdelete(PG_FUNCTION_ARGS)
if (stats == NULL)
stats = (GistBulkDeleteResult *) palloc0(sizeof(GistBulkDeleteResult));
/* we'll re-count the tuples each time */
stats->std.estimated_count = false;
stats->std.num_index_tuples = 0;
stack = (GistBDItem *) palloc0(sizeof(GistBDItem));

5
src/backend/access/hash/hash.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.110 2009/05/05 19:36:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.111 2009/06/06 22:13:50 tgl Exp $
*
* NOTES
* This file contains only the public interface routines.
@ -610,6 +610,8 @@ loop_top:
/*
* Otherwise, our count is untrustworthy since we may have
* double-scanned tuples in split buckets. Proceed by dead-reckoning.
* (Note: we still return estimated_count = false, because using this
* count is better than not updating reltuples at all.)
*/
if (metap->hashm_ntuples > tuples_removed)
metap->hashm_ntuples -= tuples_removed;
@ -623,6 +625,7 @@ loop_top:
/* return statistics */
if (stats == NULL)
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
stats->estimated_count = false;
stats->num_index_tuples = num_index_tuples;
stats->tuples_removed += tuples_removed;
/* hashvacuumcleanup will fill in num_pages */

10
src/backend/access/nbtree/nbtree.c
View File

@ -12,7 +12,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.169 2009/05/05 19:36:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtree.c,v 1.170 2009/06/06 22:13:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -579,10 +579,11 @@ btvacuumcleanup(PG_FUNCTION_ARGS)
/*
* During a non-FULL vacuum it's quite possible for us to be fooled by
* concurrent page splits into double-counting some index tuples, so
* disbelieve any total that exceeds the underlying heap's count. (We
* can't check this during btbulkdelete.)
* disbelieve any total that exceeds the underlying heap's count ...
* if we know that accurately. Otherwise this might just make matters
* worse.
*/
if (!info->vacuum_full)
if (!info->vacuum_full && !info->estimated_count)
{
if (stats->num_index_tuples > info->num_heap_tuples)
stats->num_index_tuples = info->num_heap_tuples;
@ -618,6 +619,7 @@ btvacuumscan(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
* Reset counts that will be incremented during the scan; needed in case
* of multiple scans during a single VACUUM command
*/
stats->estimated_count = false;
stats->num_index_tuples = 0;
stats->pages_deleted = 0;

5
src/backend/catalog/index.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.316 2009/05/31 20:55:37 tgl Exp $
* $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.317 2009/06/06 22:13:51 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -1938,8 +1938,9 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
ivinfo.index = indexRelation;
ivinfo.vacuum_full = false;
ivinfo.analyze_only = false;
ivinfo.estimated_count = true;
ivinfo.message_level = DEBUG2;
ivinfo.num_heap_tuples = -1;
ivinfo.num_heap_tuples = heapRelation->rd_rel->reltuples;
ivinfo.strategy = NULL;
state.tuplesort = tuplesort_begin_datum(TIDOID,

5
src/backend/commands/analyze.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.137 2009/05/19 08:30:00 heikki Exp $
* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.138 2009/06/06 22:13:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -498,8 +498,9 @@ cleanup:
ivinfo.index = Irel[ind];
ivinfo.vacuum_full = false;
ivinfo.analyze_only = true;
ivinfo.estimated_count = true;
ivinfo.message_level = elevel;
ivinfo.num_heap_tuples = -1; /* not known for sure */
ivinfo.num_heap_tuples = onerel->rd_rel->reltuples;
ivinfo.strategy = vac_strategy;
stats = index_vacuum_cleanup(&ivinfo, NULL);

34
src/backend/commands/vacuum.c
View File

@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.387 2009/03/31 22:12:48 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.388 2009/06/06 22:13:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -3389,6 +3389,7 @@ scan_index(Relation indrel, double num_tuples)
ivinfo.index = indrel;
ivinfo.vacuum_full = true;
ivinfo.analyze_only = false;
ivinfo.estimated_count = false;
ivinfo.message_level = elevel;
ivinfo.num_heap_tuples = num_tuples;
ivinfo.strategy = vac_strategy;
@ -3398,10 +3399,14 @@ scan_index(Relation indrel, double num_tuples)
if (!stats)
return;
/* now update statistics in pg_class */
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
/*
* Now update statistics in pg_class, but only if the index says the
* count is accurate.
*/
if (!stats->estimated_count)
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
ereport(elevel,
(errmsg("index \"%s\" now contains %.0f row versions in %u pages",
@ -3417,7 +3422,8 @@ scan_index(Relation indrel, double num_tuples)
* Check for tuple count mismatch. If the index is partial, then it's OK
* for it to have fewer tuples than the heap; else we got trouble.
*/
if (stats->num_index_tuples != num_tuples)
if (!stats->estimated_count &&
stats->num_index_tuples != num_tuples)
{
if (stats->num_index_tuples > num_tuples ||
!vac_is_partial_index(indrel))
@ -3456,6 +3462,7 @@ vacuum_index(VacPageList vacpagelist, Relation indrel,
ivinfo.index = indrel;
ivinfo.vacuum_full = true;
ivinfo.analyze_only = false;
ivinfo.estimated_count = false;
ivinfo.message_level = elevel;
ivinfo.num_heap_tuples = num_tuples + keep_tuples;
ivinfo.strategy = vac_strategy;
@ -3469,10 +3476,14 @@ vacuum_index(VacPageList vacpagelist, Relation indrel,
if (!stats)
return;
/* now update statistics in pg_class */
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
/*
* Now update statistics in pg_class, but only if the index says the
* count is accurate.
*/
if (!stats->estimated_count)
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
ereport(elevel,
(errmsg("index \"%s\" now contains %.0f row versions in %u pages",
@ -3490,7 +3501,8 @@ vacuum_index(VacPageList vacpagelist, Relation indrel,
* Check for tuple count mismatch. If the index is partial, then it's OK
* for it to have fewer tuples than the heap; else we got trouble.
*/
if (stats->num_index_tuples != num_tuples + keep_tuples)
if (!stats->estimated_count &&
stats->num_index_tuples != num_tuples + keep_tuples)
{
if (stats->num_index_tuples > num_tuples + keep_tuples ||
!vac_is_partial_index(indrel))

30
src/backend/commands/vacuumlazy.c
View File

@ -29,7 +29,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.119 2009/03/24 20:17:14 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuumlazy.c,v 1.120 2009/06/06 22:13:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -84,9 +84,11 @@ typedef struct LVRelStats
{
/* hasindex = true means two-pass strategy; false means one-pass */
bool hasindex;
bool scanned_all; /* have we scanned all pages (this far)? */
/* Overall statistics about rel */
BlockNumber rel_pages;
double rel_tuples;
double old_rel_tuples; /* previous value of pg_class.reltuples */
double rel_tuples; /* counts only tuples on scanned pages */
BlockNumber pages_removed;
double tuples_deleted;
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
@ -96,7 +98,6 @@ typedef struct LVRelStats
int max_dead_tuples; /* # slots allocated in array */
ItemPointer dead_tuples; /* array of ItemPointerData */
int num_index_scans;
bool scanned_all; /* have we scanned all pages (this far)? */
} LVRelStats;
@ -174,8 +175,9 @@ lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats));
vacrelstats->num_index_scans = 0;
vacrelstats->scanned_all = true; /* will be cleared if we skip a page */
vacrelstats->old_rel_tuples = onerel->rd_rel->reltuples;
vacrelstats->num_index_scans = 0;
/* Open all indexes of the relation */
vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &Irel);
@ -876,9 +878,9 @@ lazy_vacuum_index(Relation indrel,
ivinfo.index = indrel;
ivinfo.vacuum_full = false;
ivinfo.analyze_only = false;
ivinfo.estimated_count = true;
ivinfo.message_level = elevel;
/* We don't yet know rel_tuples, so pass -1 */
ivinfo.num_heap_tuples = -1;
ivinfo.num_heap_tuples = vacrelstats->old_rel_tuples;
ivinfo.strategy = vac_strategy;
/* Do bulk deletion */
@ -908,8 +910,10 @@ lazy_cleanup_index(Relation indrel,
ivinfo.index = indrel;
ivinfo.vacuum_full = false;
ivinfo.analyze_only = false;
ivinfo.estimated_count = !vacrelstats->scanned_all;
ivinfo.message_level = elevel;
ivinfo.num_heap_tuples = vacrelstats->rel_tuples;
/* use rel_tuples only if we scanned all pages, else fall back */
ivinfo.num_heap_tuples = vacrelstats->scanned_all ? vacrelstats->rel_tuples : vacrelstats->old_rel_tuples;
ivinfo.strategy = vac_strategy;
stats = index_vacuum_cleanup(&ivinfo, stats);
@ -917,10 +921,14 @@ lazy_cleanup_index(Relation indrel,
if (!stats)
return;
/* now update statistics in pg_class */
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
/*
* Now update statistics in pg_class, but only if the index says the
* count is accurate.
*/
if (!stats->estimated_count)
vac_update_relstats(indrel,
stats->num_pages, stats->num_index_tuples,
false, InvalidTransactionId);
ereport(elevel,
(errmsg("index \"%s\" now contains %.0f row versions in %u pages",

9
src/backend/postmaster/pgstat.c
View File

@ -13,7 +13,7 @@
*
* Copyright (c) 2001-2009, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.187 2009/01/01 17:23:46 momjian Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.188 2009/06/06 22:13:51 tgl Exp $
* ----------
*/
#include "postgres.h"
@ -3774,6 +3774,13 @@ pgstat_recv_vacuum(PgStat_MsgVacuum *msg, int len)
{
if (msg->m_scanned_all)
tabentry->last_anl_tuples = msg->m_tuples;
else
{
/* last_anl_tuples must never exceed n_live_tuples+n_dead_tuples */
tabentry->last_anl_tuples = Min(tabentry->last_anl_tuples,
tabentry->n_live_tuples);
}
if (msg->m_autovacuum)
tabentry->autovac_analyze_timestamp = msg->m_vacuumtime;
else

14
src/include/access/genam.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/genam.h,v 1.76 2009/03/24 20:17:14 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/genam.h,v 1.77 2009/06/06 22:13:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -34,14 +34,17 @@ typedef struct IndexBuildResult
/*
* Struct for input arguments passed to ambulkdelete and amvacuumcleanup
*
* Note that num_heap_tuples will not be valid during ambulkdelete,
* only amvacuumcleanup.
* num_heap_tuples is accurate only when estimated_count is false;
* otherwise it's just an estimate (currently, the estimate is the
* prior value of the relation's pg_class.reltuples field). It will
* always just be an estimate during ambulkdelete.
*/
typedef struct IndexVacuumInfo
{
Relation index; /* the index being vacuumed */
bool vacuum_full; /* VACUUM FULL (we have exclusive lock) */
bool analyze_only; /* ANALYZE (without any actual vacuum) */
bool estimated_count; /* num_heap_tuples is an estimate */
int message_level; /* ereport level for progress messages */
double num_heap_tuples; /* tuples remaining in heap */
BufferAccessStrategy strategy; /* access strategy for reads */
@ -60,12 +63,15 @@ typedef struct IndexVacuumInfo
*
* Note: pages_removed is the amount by which the index physically shrank,
* if any (ie the change in its total size on disk). pages_deleted and
* pages_free refer to free space within the index file.
* pages_free refer to free space within the index file. Some index AMs
* may compute num_index_tuples by reference to num_heap_tuples, in which
* case they should copy the estimated_count field from IndexVacuumInfo.
*/
typedef struct IndexBulkDeleteResult
{
BlockNumber num_pages; /* pages remaining in index */
BlockNumber pages_removed; /* # removed during vacuum operation */
bool estimated_count; /* num_index_tuples is an estimate */
double num_index_tuples; /* tuples remaining */
double tuples_removed; /* # removed during vacuum operation */
BlockNumber pages_deleted; /* # unused pages in index */