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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/optimizer/util/pathnode.c | |
| parent | caa1054df8408b165e5f66ff25c87b6dd0a0a1e7 (diff) | |
| download | postgresql-a2822fb9337a21f98ac4ce850bb4145acf47ca27.tar.gz postgresql-a2822fb9337a21f98ac4ce850bb4145acf47ca27.zip | |
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/optimizer/util/pathnode.c')
| -rw-r--r-- | src/backend/optimizer/util/pathnode.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index 4a1c94affbd..8ed55a3d0e2 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -25,8 +25,8 @@ #include "optimizer/paths.h" #include "optimizer/tlist.h" #include "parser/parsetree.h" -#include "utils/selfuncs.h" #include "utils/lsyscache.h" +#include "utils/selfuncs.h" static List *translate_sub_tlist(List *tlist, int relid); @@ -418,6 +418,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel) * 'indexscandir' is ForwardScanDirection or BackwardScanDirection * for an ordered index, or NoMovementScanDirection for * an unordered index. + * 'indexonly' is true if an index-only scan is wanted. * 'outer_rel' is the outer relation if this is a join inner indexscan path. * (pathkeys and indexscandir are ignored if so.) NULL if not. * @@ -430,6 +431,7 @@ create_index_path(PlannerInfo *root, List *indexorderbys, List *pathkeys, ScanDirection indexscandir, + bool indexonly, RelOptInfo *outer_rel) { IndexPath *pathnode = makeNode(IndexPath); @@ -468,6 +470,7 @@ create_index_path(PlannerInfo *root, pathnode->isjoininner = (outer_rel != NULL); pathnode->indexscandir = indexscandir; + pathnode->indexonly = indexonly; if (outer_rel != NULL) { @@ -506,7 +509,8 @@ create_index_path(PlannerInfo *root, pathnode->rows = rel->rows; } - cost_index(pathnode, root, index, indexquals, indexorderbys, outer_rel); + cost_index(pathnode, root, index, indexquals, indexorderbys, + indexonly, outer_rel); return pathnode; } |