From 46d98da43e56aa407242fc5ca6c0303f160cd936 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 2 Mar 2018 11:22:42 -0500 Subject: [PATCH] Make gistvacuumcleanup() count the actual number of index tuples. Previously, it just returned the heap tuple count, which might be only an estimate, and would be completely the wrong thing if the index is partial. Since this function scans every index page anyway to find free pages, it's practically free to count the surviving index tuples. Let's do that and return an accurate count. This is easily visible as a wrong reltuples value for a partial GiST index following VACUUM, so back-patch to all supported branches. Andrey Borodin, reviewed by Michail Nikolaev Discussion: https://postgr.es/m/151956654251.6915.675951950408204404.pgcf@coridan.postgresql.org --- src/backend/access/gist/gistvacuum.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/src/backend/access/gist/gistvacuum.c b/src/backend/access/gist/gistvacuum.c index 1c4e2c19b76..14202fa25ed 100644 --- a/src/backend/access/gist/gistvacuum.c +++ b/src/backend/access/gist/gistvacuum.c @@ -34,6 +34,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS) BlockNumber npages, blkno; BlockNumber totFreePages; + double tuplesCount; bool needLock; /* No-op in ANALYZE ONLY mode */ @@ -42,17 +43,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS) /* Set up all-zero stats if gistbulkdelete wasn't called */ if (stats == NULL) - { stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult)); - /* use heap's tuple count */ - stats->num_index_tuples = info->num_heap_tuples; - stats->estimated_count = info->estimated_count; - - /* - * XXX the above is wrong if index is partial. Would it be OK to just - * return NULL, or is there work we must do below? - */ - } /* * Need lock unless it's local to this backend. @@ -67,6 +58,7 @@ gistvacuumcleanup(PG_FUNCTION_ARGS) UnlockRelationForExtension(rel, ExclusiveLock); totFreePages = 0; + tuplesCount = 0; for (blkno = GIST_ROOT_BLKNO + 1; blkno < npages; blkno++) { Buffer buffer; @@ -84,6 +76,11 @@ gistvacuumcleanup(PG_FUNCTION_ARGS) totFreePages++; RecordFreeIndexPage(rel, blkno); } + else if (GistPageIsLeaf(page)) + { + /* count tuples in index (considering only leaf tuples) */ + tuplesCount += PageGetMaxOffsetNumber(page); + } UnlockReleaseBuffer(buffer); } @@ -97,6 +94,8 @@ gistvacuumcleanup(PG_FUNCTION_ARGS) stats->num_pages = RelationGetNumberOfBlocks(rel); if (needLock) UnlockRelationForExtension(rel, ExclusiveLock); + stats->num_index_tuples = tuplesCount; + stats->estimated_count = false; PG_RETURN_POINTER(stats); }