Re: EXPLAIN ANALYZE of BRIN bitmap index scan with disjunction - Mailing list pgsql-performance

On Thu, Jun 20, 2019 at 12:09:13PM -0600, Michael Lewis wrote:
> For kicks I tried the example given and got the below which seems more
> expected.

Do you just mean that it ran faster the 2nd time ?  Isn't that just due just to
cache effects ?  Rerun them both back to back.

See that the "actual" rowcount of the Index Scan is higher with tigher
condition:

>   ->  Bitmap Index Scan on idx_brin_test_brin  (cost=0.00..3.32 rows=14286 width=0) (actual time=0.018..0.019
rows=640loops=1)
 
>         Index Cond: (id >= 90000)

>   ->  Bitmap Index Scan on idx_brin_test_brin  (cost=0.00..3.31 rows=7143 width=0) (actual time=0.026..0.027
rows=1280loops=1)
 
>         Index Cond: ((id >= 90000) AND (r = ANY ('{1,3}'::integer[])))