Hi, I have a table named "gps", with an indexed column "packettime", which has unix timestamps.
The following query: select * from gps where packettime < extract(epoch from '2017-05-01 08:00+08'::timestamp with time zone) explains to: Seq Scan on gps (cost=0.00..43411860.64 rows=384325803 width=120) Filter: ((packettime)::double precision < date_part('epoch'::text, '2017-05-01 08:00:00+08'::timestamp with time zone)) While this query: select * from gps where packettime < 1493596800 explains to: Index Scan using idx_gps_packettime on gps (cost=0.58..2661058.92 rows=8912880 width=120) Index Cond: (packettime < 1493596800) The above behaviour is the same whether the query is long or short. PostgreSQL doesn't seem like to pre-compute the function value. So how can I make it pre-compute the timestamp and use the index, or I have to manually calculate the timestamp? Is this an intended behaviour? -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general