postgresql - Postegres: Queries with INTERVAL operation don work over constraints -

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just in matter of simplification, have following query:

select * table (date_trunc('day',create_time ) > now() - interval '2 days');

running explain got this:

->  seq scan on table  (cost=0.00..1.62 rows=10 width=232)                filter: (date_trunc('day'::text, create_time) > (now() - '2 days'::**interval**))

as i've highlighted, operation (now() - interval '2 days') returns interval, need timestamp.

in case, how can convert interval timestamp or thing ?

thank answers, think not explained, here's detailed problem:

for performance purposes, have here table named 'transactions' , child tables each day, example 'transactions_2015_05_29'.

on each child table have following constraint:

constraint transactions_2015_05_29_create_time_check check (date_trunc('day'::text, create_time) = '2015-05-29 00:00:00'::timestamp without time zone)

when run following 'explain' following query this:

explain:

explain select * pp_transactions (date_trunc('day', create_row_time) < current_date + interval '1 day');  "result  (cost=0.00..120.52 rows=731 width=232)" "  ->  append  (cost=0.00..120.52 rows=731 width=232)" "        ->  seq scan on transactions  (cost=0.00..1.70 rows=10 width=232)" "              filter: (date_trunc('day'::text, create_time) < (('now'::text)::date + '1 day'::interval))" "        ->  seq scan on **transactions_2015_05_28** pp_transactions  (cost=0.00..14.65 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < '2015-05-30 00:00:00'::timestamp without time zone)" "        ->  seq scan on **transactions_2015_05_29** transactions  (cost=0.00..16.98 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < (('now'::text)::date + '1 day'::interval))" "        ->  seq scan on **transactions_2015_05_30** transactions  (cost=0.00..16.98 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < (('now'::text)::date + '1 day'::interval))" "        ->  seq scan on **transactions_2015_05_31** transactions  (cost=0.00..16.98 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < (('now'::text)::date + '1 day'::interval))"

as can see, there tables should not there. if run following query correct result on explain:

explain:

explain select * pp_transactions (date_trunc('day', create_row_time) < '2015-05-30 00:00:00');  "result  (cost=0.00..30.76 rows=216 width=232)" "  ->  append  (cost=0.00..30.76 rows=216 width=232)" "        ->  seq scan on transactions  (cost=0.00..1.46 rows=10 width=232)" "              filter: (date_trunc('day'::text, create_time) < '2015-05-30 00:00:00'::timestamp without time zone)" "        ->  seq scan on **transactions_2015_05_28** pp_transactions  (cost=0.00..14.65 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < '2015-05-30 00:00:00'::timestamp without time zone)" "        ->  seq scan on **transactions_2015_05_29** pp_transactions  (cost=0.00..14.65 rows=103 width=232)" "              filter: (date_trunc('day'::text, create_time) < '2015-05-30 00:00:00'::timestamp without time zone)"

so, first query must behave second one.

from postgres manual:

  1. you may add or subtract interval timestamp produce timestamp

timestamp '1999-12-11' + interval '19 days' = timestamp '1999-12-30'

and looks date me (2 days ago @ 19:08 cest), , according manual (once again) now() produces timestamp:

 (now() - '2 days'::**interval**)

now() function , '2 days' interval.


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