The context for this is that I was looking at cases where btree indexes were not using all the columns they could, but rather shoving some of the conditions down into a Filter unnecessarily/unhelpfully. This change doesn't fix that, but it does seem to be moving in the right direction.
Added to commitfest.
This does cause a regression test failure due to an (apparently?) uninteresting plan change.
Looking more at the regression test plan change, it points up an interesting question which is only tangentially related to this patch.
With patch applied:
[local] 417536 regression=# explain analyze SELECT thousand, tenthous FROM tenk1 WHERE thousand < 2 AND tenthous IN (1001,3000) ORDER BY thousand; QUERY PLAN --------------------------------------------------------------------------------------------------------------------------------------- Sort (cost=4.55..4.56 rows=1 width=8) (actual time=0.100..0.101 rows=2 loops=1) Sort Key: thousand Sort Method: quicksort Memory: 25kB -> Index Only Scan using tenk1_thous_tenthous on tenk1 (cost=0.29..4.50 rows=1 width=8) (actual time=0.044..0.048 rows=2 loops=1) Index Cond: ((thousand < 2) AND (tenthous = ANY ('{1001,3000}'::integer[]))) Heap Fetches: 0 Planning Time: 1.040 ms Execution Time: 0.149 ms (8 rows)
[local] 417536 regression=# set enable_sort TO off ;
[local] 417536 regression=# explain analyze SELECT thousand, tenthous FROM tenk1 WHERE thousand < 2 AND tenthous IN (1001,3000) ORDER BY thousand; QUERY PLAN --------------------------------------------------------------------------------------------------------------------------------- Index Only Scan using tenk1_thous_tenthous on tenk1 (cost=0.29..4.71 rows=1 width=8) (actual time=0.021..0.024 rows=2 loops=1) Index Cond: (thousand < 2) Filter: (tenthous = ANY ('{1001,3000}'::integer[])) Rows Removed by Filter: 18 Heap Fetches: 0 Planning Time: 0.156 ms Execution Time: 0.039 ms (7 rows)
Why does having the =ANY in the "Index Cond:" rather than the "Filter:" inhibit it from understanding that the rows will still be delivered in order by "thousand"?
