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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-07 20:13:02 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-07 20:14:13 -0400 |
| commit | a2822fb9337a21f98ac4ce850bb4145acf47ca27 (patch) | |
| tree | c239fe9a32ff0225e906711a76348cee1567f0d8 /src/backend/access/index/genam.c | |
| parent | caa1054df8408b165e5f66ff25c87b6dd0a0a1e7 (diff) | |
| download | postgresql-a2822fb9337a21f98ac4ce850bb4145acf47ca27.tar.gz | |
Support index-only scans using the visibility map to avoid heap fetches.
When a btree index contains all columns required by the query, and the
visibility map shows that all tuples on a target heap page are
visible-to-all, we don't need to fetch that heap page. This patch depends
on the previous patches that made the visibility map reliable.
There's a fair amount left to do here, notably trying to figure out a less
chintzy way of estimating the cost of an index-only scan, but the core
functionality seems ready to commit.
Robert Haas and Ibrar Ahmed, with some previous work by Heikki Linnakangas.
Diffstat (limited to 'src/backend/access/index/genam.c')
| -rw-r--r-- | src/backend/access/index/genam.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 98832adb8a..236e48912b 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -93,6 +93,8 @@ RelationGetIndexScan(Relation indexRelation, int nkeys, int norderbys) else scan->orderByData = NULL; + scan->xs_want_itup = false; /* may be set later */ + /* * During recovery we ignore killed tuples and don't bother to kill them * either. We do this because the xmin on the primary node could easily be @@ -109,6 +111,8 @@ RelationGetIndexScan(Relation indexRelation, int nkeys, int norderbys) scan->opaque = NULL; + scan->xs_itup = NULL; + ItemPointerSetInvalid(&scan->xs_ctup.t_self); scan->xs_ctup.t_data = NULL; scan->xs_cbuf = InvalidBuffer; |