Re: Query with rightmost function does not use index

Here are the EXPLAIN ANALYZE outputs:

explain analyze select * from filter_item where filter_hash = MD5('');

QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
Seq Scan on filter_item (cost=0.00..424644.96 rows=86108 width=49) (actual time=8177.807..12421.921 rows=77 loops=1)
Filter: ((filter_hash)::text = 'd41d8cd98f00b204e9800998ecf8427e'::text)
Total runtime: 12421.959 ms
(3 rows)

explain analyze select * from filter_item where filter_hash = 'd41d8cd98f00b204e9800998ecf8427e'

QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on filter_item (cost=77.92..6609.02 rows=3534 width=49) (actual time=0.055..0.100 rows=77 loops=1)
Recheck Cond: (filter_hash = 'd41d8cd98f00b204e9800998ecf8427e'::bpchar)
-> Bitmap Index Scan on filter_item__filter_hash (cost=0.00..77.04 rows=3534 width=0) (actual time=0.049..0.049 rows=77 loops=1)
Index Cond: (filter_hash = 'd41d8cd98f00b204e9800998ecf8427e'::bpchar)
Total runtime: 0.130 ms
(5 rows)