From: Kaloyan Iliev <news1@faith.digsys.bg>
To: pgsql-performance@postgresql.org
Subject: Query not using index
Date: Fri, 09 Dec 2005 11:36:10 +0200
Message-ID: <4399500A.4020607@faith.digsys.bg> (raw)
Hi all,
I have a problem with a query which doeson't want to use indexes. I
tried to create different indexes but nothing help. Can anyone suggest
what index I need.
This query is executed 1.5Milion times per day and I need it to be veri
fast. I made my test on 8.0.0 beta but the production database is still
7.4.6 so i need suggestions for 7.4.6.
I will post the table with the indexes and the query plans.
iplog=# \d croute
Table "public.croute"
Column | Type | Modifiers
-----------------+--------------------------+-----------
confid | integer |
network | cidr |
comment | text |
router | text |
port | text |
valid_at | timestamp with time zone |
archived_at | timestamp with time zone |
Indexes:
"croute_netwo" btree (network) WHERE confid > 0 AND archived_at IS NULL
"croute_netwokr_valid_at" btree (network, valid_at)
"croute_network" btree (network) WHERE archived_at IS NULL
"croute_network_all" btree (network)
iplog=# select version();
version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 8.0.0beta1 on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
3.3.2 (Mandrake Linux 10.0 3.3.2-6mdk)
(1 row)
!!!!!!!!!!!!THIS IS THE QUERY!!!!!!!!!!!!!!!!!
customer=> explain analyze SELECT *
customer-> FROM croute
customer-> WHERE '193.68.0.8/32' <<=
network AND
customer-> (archived_at is NULL
OR archived_at > '17-11-2005') AND
customer-> valid_at <
'1-12-2005'::date AND
customer-> confid > 0;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on croute (cost=0.00..441.62 rows=413 width=102) (actual
time=14.131..37.515 rows=1 loops=1)
Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
zone)) AND (valid_at < ('2005-12-01'::date)::timestamp with time zone)
AND (confid > 0))
Total runtime: 37.931 ms
(3 rows)
customer=> select count(*) from croute;
count
-------
10066
(1 row)
This is the result of the query:
confid | network | comment | router | port |
valid_at | archived_at |
-------+---------------+---------+------+----+-------------------------+-----------+
19971 | xx.xx.xx.xx/32 | xxxxx | ? | ? | 2005-03-11
00:00:00+02 | |
(1 row)
And last I try to stop the sequance scan but it doesn't help. I suppose
I don't have the right index.
iplog=# set enable_seqscan = off;
SET
iplog=# explain analyze SELECT *
iplog-# FROM croute
iplog-# WHERE '193.68.0.8/32' <<=
network AND
iplog-# (archived_at is NULL OR
archived_at > '17-11-2005') AND
iplog-# valid_at <
'1-12-2005'::date AND
iplog-# confid > 0;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on croute (cost=100000000.00..100000780.64 rows=1030
width=103) (actual time=29.593..29.819 rows=1 loops=1)
Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
zone)) AND (valid_at < '2005-12-01'::date) AND (confid > 0))
Total runtime: 29.931 ms
(3 rows)
I try creating one last index on all fields but it doesn't help.
iplog=# CREATE INDEX croute_all on
croute(network,archived_at,valid_at,confid);
CREATE INDEX
iplog=# explain analyze SELECT *
iplog-# FROM croute
iplog-# WHERE '193.68.0.8/32' <<=
network AND
iplog-# (archived_at is NULL OR
archived_at > '17-11-2005') AND
iplog-# valid_at <
'1-12-2005'::date AND
iplog-# confid > 0;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on croute (cost=100000000.00..100000780.64 rows=1030
width=103) (actual time=29.626..29.879 rows=1 loops=1)
Filter: (('193.68.0.8/32'::cidr <<= network) AND ((archived_at IS
NULL) OR (archived_at > '2005-11-17 00:00:00+02'::timestamp with time
zone)) AND (valid_at < '2005-12-01'::date) AND (confid > 0))
Total runtime: 30.060 ms
(3 rows)
Thanks in advance to all.
Kaloyan Iliev
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Subject: Re: Query not using index
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