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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-11 14:20:06 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-11 14:21:30 -0400 |
| commit | a0185461dd94c8d31d8d55a7f2839b0d2f172ab9 (patch) | |
| tree | 3bd68d4e123336bbdefa8fd92372f0af7fb6d64f /src/backend/optimizer/path/indxpath.c | |
| parent | fa351d5a0db0672b6f586315720302e493116f27 (diff) | |
| download | postgresql-a0185461dd94c8d31d8d55a7f2839b0d2f172ab9.tar.gz postgresql-a0185461dd94c8d31d8d55a7f2839b0d2f172ab9.zip | |
Rearrange the implementation of index-only scans.
This commit changes index-only scans so that data is read directly from the
index tuple without first generating a faux heap tuple. The only immediate
benefit is that indexes on system columns (such as OID) can be used in
index-only scans, but this is necessary infrastructure if we are ever to
support index-only scans on expression indexes. The executor is now ready
for that, though the planner still needs substantial work to recognize
the possibility.
To do this, Vars in index-only plan nodes have to refer to index columns
not heap columns. I introduced a new special varno, INDEX_VAR, to mark
such Vars to avoid confusion. (In passing, this commit renames the two
existing special varnos to OUTER_VAR and INNER_VAR.) This allows
ruleutils.c to handle them with logic similar to what we use for subplan
reference Vars.
Since index-only scans are now fundamentally different from regular
indexscans so far as their expression subtrees are concerned, I also chose
to change them to have their own plan node type (and hence, their own
executor source file).
Diffstat (limited to 'src/backend/optimizer/path/indxpath.c')
| -rw-r--r-- | src/backend/optimizer/path/indxpath.c | 23 |
1 files changed, 11 insertions, 12 deletions
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c index 7090a7e0c0d..9ab146a1f74 100644 --- a/src/backend/optimizer/path/indxpath.c +++ b/src/backend/optimizer/path/indxpath.c @@ -199,14 +199,15 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel) true, NULL, SAOP_FORBID, ST_ANYSCAN); /* - * Submit all the ones that can form plain IndexScan plans to add_path. (A - * plain IndexPath always represents a plain IndexScan plan; however some - * of the indexes might support only bitmap scans, and those we mustn't - * submit to add_path here.) Also, pick out the ones that might be useful - * as bitmap scans. For that, we must discard indexes that don't support - * bitmap scans, and we also are only interested in paths that have some - * selectivity; we should discard anything that was generated solely for - * ordering purposes. + * Submit all the ones that can form plain IndexScan plans to add_path. + * (A plain IndexPath might represent either a plain IndexScan or an + * IndexOnlyScan, but for our purposes here the distinction does not + * matter. However, some of the indexes might support only bitmap scans, + * and those we mustn't submit to add_path here.) Also, pick out the ones + * that might be useful as bitmap scans. For that, we must discard + * indexes that don't support bitmap scans, and we also are only + * interested in paths that have some selectivity; we should discard + * anything that was generated solely for ordering purposes. */ bitindexpaths = NIL; foreach(l, indexpaths) @@ -1107,11 +1108,9 @@ check_index_only(RelOptInfo *rel, IndexOptInfo *index) /* * For the moment, we just ignore index expressions. It might be nice - * to do something with them, later. We also ignore index columns - * that are system columns (such as OID), because the virtual-tuple - * coding used by IndexStoreHeapTuple() can't deal with them. + * to do something with them, later. */ - if (attno <= 0) + if (attno == 0) continue; index_attrs = |