Try this after deleting:
VACUUM ANALYZE test2;
I suggest to activate autovacuum in your postgresql.conf, so you won't have to analyze table by hand.
-----Original Message-----
From: Kumar Anand <kumar.anand@xxxxxxxxxxxxxx>
To: pgsql-admin@xxxxxxxxxxxxxx
Subject: select count is too slow
Date: Thu, 20 Aug 2009 15:06:45 +0530
Dear all,
I face this problem from last few days.
here is test2 table with only one column id
erp_test=> \d test2
Table "public.test2"
Column | Type | Modifiers
--------+---------+-----------
id | integer |
I insert 10,000,000 entries in this table.
erp_test=> INSERT INTO test2 VALUES (generate_series(1,10000000));
INSERT 0 10000000
then i delete all the entries
erp_test=> delete from test2;
DELETE 10000000
and i insert only 10 entries
erp_test=> INSERT INTO test2 VALUES (generate_series(1,10));
INSERT 0 10
now i try to count no of rows in this table which take long time for
this 10 rows only
(about 2-3 second)
erp_test=> SELECT count(*) from test2;
count
-------
10
(1 row)
this is the output of explain analyze query of the same
erp_test=> EXPLAIN ANALYZE SELECT count(*) from test2;
QUERY
PLAN
------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=198652.13..198652.14 rows=1 width=0) (actual
time=2123.471..2123.472 rows=1 loops=1)
-> Seq Scan on test2 (cost=0.00..169732.70 rows=11567770 width=0)
(actual time=2123.454..2123.454 rows=10 loops=1)
Total runtime: 2123.609 ms
(3 rows)
can any one solve my problem to speed up my select count query.
--
Thanks & Regards
Kumar Anand
