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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
This commit is contained in:
Tom Lane 2018-03-02 11:22:42 -05:00
parent 7240962f86
commit 81b9b5ce49
1 changed files with 9 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/backend/access/gist/gistvacuum.c
View File

@ -32,6 +32,7 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
BlockNumber npages, BlockNumber npages,
blkno; blkno;
BlockNumber totFreePages; BlockNumber totFreePages;
double tuplesCount;
bool needLock; bool needLock;
/* No-op in ANALYZE ONLY mode */ /* No-op in ANALYZE ONLY mode */
@ -40,17 +41,7 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
/* Set up all-zero stats if gistbulkdelete wasn't called */ /* Set up all-zero stats if gistbulkdelete wasn't called */
if (stats == NULL) if (stats == NULL)
{
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult)); 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. * Need lock unless it's local to this backend.
@ -65,6 +56,7 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
UnlockRelationForExtension(rel, ExclusiveLock); UnlockRelationForExtension(rel, ExclusiveLock);
totFreePages = 0; totFreePages = 0;
tuplesCount = 0;
for (blkno = GIST_ROOT_BLKNO + 1; blkno < npages; blkno++) for (blkno = GIST_ROOT_BLKNO + 1; blkno < npages; blkno++)
{ {
Buffer buffer; Buffer buffer;
@ -82,6 +74,11 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
totFreePages++; totFreePages++;
RecordFreeIndexPage(rel, blkno); RecordFreeIndexPage(rel, blkno);
} }
else if (GistPageIsLeaf(page))
{
/* count tuples in index (considering only leaf tuples) */
tuplesCount += PageGetMaxOffsetNumber(page);
}
UnlockReleaseBuffer(buffer); UnlockReleaseBuffer(buffer);
} }
@ -95,6 +92,8 @@ gistvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
stats->num_pages = RelationGetNumberOfBlocks(rel); stats->num_pages = RelationGetNumberOfBlocks(rel);
if (needLock) if (needLock)
UnlockRelationForExtension(rel, ExclusiveLock); UnlockRelationForExtension(rel, ExclusiveLock);
stats->num_index_tuples = tuplesCount;
stats->estimated_count = false;
return stats; return stats;
} }