]> granicus.if.org Git - postgresql/commitdiff
Improve the IndexVacuumInfo/IndexBulkDeleteResult API to allow somewhat sane
authorTom Lane <tgl@sss.pgh.pa.us>
Sat, 6 Jun 2009 22:13:52 +0000 (22:13 +0000)
committerTom Lane <tgl@sss.pgh.pa.us>
Sat, 6 Jun 2009 22:13:52 +0000 (22:13 +0000)
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.

src/backend/access/gin/ginvacuum.c
src/backend/access/gist/gistvacuum.c
src/backend/access/hash/hash.c
src/backend/access/nbtree/nbtree.c
src/backend/catalog/index.c
src/backend/commands/analyze.c
src/backend/commands/vacuum.c
src/backend/commands/vacuumlazy.c
src/backend/postmaster/pgstat.c
src/include/access/genam.h

index dd98b9fd2842ad7960d16ef9e975378c1f997f84..934bf7c36282badf1ce1f9658b47cdb5a6c8968d 100644 (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,
index 01b8512d070b80f892e21da976021d19138fa87f..833e6c574eb8db0b55b0f446d99ac69b822628d3 100644 (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));
index 58cccb6e7244a7ba5b0aafb20d9e112042304ced..4c1cd5ceda9acfede6752c66474a35da78e50371 100644 (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 */
index a90a0b183409c793534772970804b3ba775e3b50..55d947e9f2782fc4cba5be02367672bea56e89ea 100644 (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;
 
index c1001c0fac7c7260851eeefbc81844a7fcacfc37..1e19cbff31e01782e3d881c1c96e8f82b821a030 100644 (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,
index 5c5eb0444ddb2ecc66753a79a3ae74ce1d2e3187..d549fa3bb9f9aaaa1e39d5dd263411bc2854288b 100644 (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);
index 30c1972bcfc7685c550b8c9355dd16ed08ea29be..4a5ae53d484683e51f60fe99cb46c4f18ae16252 100644 (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))
index cb73cfa87a741def95ad43e3f325b8e09f47c9a3..dd0691d0fe788f802f410ad62134413dba39eede 100644 (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",
index f626b91748b2cf54bdbd2b56fd18c3fada520e72..4925e6b3b85720771f2eff0fe1c82206f9d8a539 100644 (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
index 65fd7f73310c4e88b6fe4aa310eef916b9180005..868980e32668b4d35a1d91a2b114f2792b99156d 100644 (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 */