On 09/15/11 12:53 AM, Yang Zhang wrote:
mydb=# explain select user_id from den where user_id not in (select
duid from user_mappings) and timestamp between '2009-04-01' and
'2010-04-01';
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on den (cost=711.58..66062724212.74 rows=22634720 width=4)
Filter: (("timestamp">= '2009-04-01 00:00:00'::timestamp without
time zone) AND ("timestamp"<= '2010-04-01 00:00:00'::timestamp
without time zone) AND (NOT (SubPlan 1)))
SubPlan 1
-> Materialize (cost=711.58..1223.38 rows=36780 width=4)
-> Seq Scan on user_mappings (cost=0.00..530.80 rows=36780 width=4)
user_mappings is fairly small:
so you have to check if every one of the 22 million rows of 'den' in
that time range and is not one of the 36000 rows of user_mappings?
how many rows are in that time range?
are timestamp and duid indexed? have the tables been analyzed any time
recently?
--
john r pierce N 37, W 122
santa cruz ca mid-left coast
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