Someone offlist reported query slowness because we don't convert
function calls with all-constant parameters to be a constants before we
start a sequential scan:
EXPLAIN SELECT * FROM test WHERE x >= to_date('2001-01-01', 'YYYY-MM-DD') AND x <= to_date('2001-01-01',
'YYYY-MM-DD'); QUERY
PLAN-------------------------------------------------------------------------------------------------------------------------------
SeqScan on test (cost=0.00..58.00 rows=12 width=4) Filter: ((x >= to_date('2001-01-01'::text, 'YYYY-MM-DD'::text))
AND(x<= to_date('2001-01-01'::text, 'YYYY-MM-DD'::text)))(2 rows)
Notice the to_date()'s were not converted to constants in EXPLAIN so
they are evaluated for every row. to_date() is marked STABLE.
Is this something we should improve?
-- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB
http://enterprisedb.com
+ It's impossible for everything to be true. +
