On Wed, Mar 11, 2015 at 2:54 PM, Andrew Gierth <and...@tao11.riddles.org.uk>
wrote:
> Seq Scan on comments (cost=0.00..2406.18 rows=4140 width=792) (actual
> time=0.601..3946.589 rows=4056 loops=1)
>
> Bitmap Heap Scan on comments (cost=204.09..2404.30 rows=4140 width=792)
> (actual time=2.401..11.564 rows=4056 loops=1)
>
...
> (strangely, the seqscan plan is picked despite having a cost more than a
> point higher? what's up with that?)
>
It is probably this, from src/backend/optimizer/util/pathnode.c :
costcmp = compare_path_costs_fuzzily(new_path, old_path, 1.01,
parent_rel->consider_startup);
Cheers,
Jeff
