On Wed, Jul 17, 2019 at 02:53:20PM +0300, Sergei Kornilov wrote:
Hello
Please recheck with track_io_timing = on in configuration. explain
(analyze,buffers) with this option will report how many time we spend
during i/o
Buffers: shared hit=2 read=31492
31492 blocks / 65 sec ~ 480 IOPS, not bad if you are using HDD
Your query reads table data from disks (well, or from OS cache). You need
more RAM for shared_buffers or disks with better performance.
Either that, or try creating a covering index, so that the query can do an
index-only scan. That might reduce the amount of IO against the table, and
in the index the data should be located close to each other (same page or
pages close to each other).
So try something like
CREATE INDEX ios_idx ON table (field, user_id);
and make sure the table is vacuumed often enough (so that the visibility
map is up to date).
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
