From a0185461dd94c8d31d8d55a7f2839b0d2f172ab9 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 11 Oct 2011 14:20:06 -0400 Subject: 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). --- src/backend/executor/execScan.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'src/backend/executor/execScan.c') diff --git a/src/backend/executor/execScan.c b/src/backend/executor/execScan.c index d4ed2358564..42acc102c63 100644 --- a/src/backend/executor/execScan.c +++ b/src/backend/executor/execScan.c @@ -246,10 +246,17 @@ void ExecAssignScanProjectionInfo(ScanState *node) { Scan *scan = (Scan *) node->ps.plan; + Index varno; + + /* Vars in an index-only scan's tlist should be INDEX_VAR */ + if (IsA(scan, IndexOnlyScan)) + varno = INDEX_VAR; + else + varno = scan->scanrelid; if (tlist_matches_tupdesc(&node->ps, scan->plan.targetlist, - scan->scanrelid, + varno, node->ss_ScanTupleSlot->tts_tupleDescriptor)) node->ps.ps_ProjInfo = NULL; else -- cgit v1.2.3