5 Commits (92135ea0ed8f75daa86cd94301cedc7f5b714e3c)

Author	SHA1	Message	Date
Robert Haas	9f9135d129	Instrument index-only scans to count heap fetches performed. ... Patch by me; review by Tom Lane, Jeff Davis, and Peter Geoghegan.	14 years ago
Bruce Momjian	e126958c2e	Update copyright notices for year 2012.	14 years ago
Tom Lane	336c1d7a51	Avoid assuming that index-only scan data matches the index's rowtype. ... In general the data returned by an index-only scan should have the datatypes originally computed by FormIndexDatum. If the index opclasses use "storage" datatypes different from their input datatypes, the scan tuple will not have the same rowtype attributed to the index; but we had a hard-wired assumption that that was true in nodeIndexonlyscan.c. We'd already hacked around the issue for the one case where the types are different in btree indexes (btree name_ops), but this would definitely come back to bite us if we ever implement index-only scans in GiST. To fix, require the index AM to explicitly provide the tupdesc for the tuple it is returning. btree can just pass back the index's tupdesc, but GiST will have to work harder when and if it supports index-only scans. I had previously proposed fixing this by allowing the index AM to fill the scan tuple slot directly; but on reflection that seemed like a module layering violation, since TupleTableSlots are creatures of the executor. At least in the btree case, it would also be less efficient, since the tuple deconstruction work would occur even for rows later found to be invisible to the scan's snapshot.	14 years ago
Tom Lane	cb6771fb32	Generate index-only scan tuple descriptor from the plan node's indextlist. ... Dept. of second thoughts: as long as we've got that tlist hanging around anyway, we can apply ExecTypeFromTL to it to get a suitable descriptor for the ScanTupleSlot. This is a nicer solution than the previous one because it eliminates some hard-wired knowledge about btree name_ops, and because it avoids the somewhat shaky assumption that we needn't set up the scan tuple descriptor in EXPLAIN_ONLY mode. It doesn't change what actually happens at run-time though, and I'm still a bit nervous about that.	15 years ago
Tom Lane	a0185461dd	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).	15 years ago