Ok now that I made it so it actually *test* collisions, with the patch
it always returns all rows that matched the hashed "key". For example
(non lobotomized inthash8, I just brute forced some collisions for 0
so that anyone can try this)
create table test_hash (num int8);
insert into test_hash (num) values (0), (1805671691), (3294821164),
(4294967297);
create index test_hash_num_idx on test_hash using hash (num);
select * from test_hash where num = 0;
num
------------
0
1805671691
3294821164
4294967297
set enable_bitmapscan to off;
select * from test_hash where num = 0;
num
-----
0
CVS HEAD, 8_3_STABLE obviously work if I force the index scan
