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
-------------------------------------------------------------------------------------------------------------------------------
Seq Scan 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 <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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