pg.ddx.io pgsql-sql@postgresql.org mailing list archive help / color / mirror / Atom feed From: ries@jongert.nl
Cc: pgsql-sql@postgresql.org
Subject: Re: is this explain good or bad???
Date: Fri, 19 Sep 2003 10:02:32 +0200
Message-ID: <003101c37e84$61b54b80$fd01000a@IT001> (raw )
In-Reply-To: <3F6AA786.1080404@klaster.net >
Here are the explain analyze versions:
Best regards and thanx in advance
Ries
explain analyze select count(*) from sq_logfile;
NOTICE: QUERY PLAN:
Aggregate (cost=35988.07..35988.07 rows=1 width=0) (actual
time=71907.64..71907.64 rows=1 loops=1)
-> Seq Scan on sq_logfile (cost=0.00..33493.86 rows=997686 width=0)
(actual time=12.90..46759.12 rows=997686 loops=1)
Total runtime: 71907.76 msec
explain analyze select count(*) from sq_flogile;
NOTICE: QUERY PLAN:
Aggregate (cost=128282.68..128282.68 rows=1 width=40) (actual
time=99338.92..99338.92 rows=1 loops=1)
-> Hash Join (cost=8.65..125788.46 rows=997686 width=40) (actual
time=34.34..93123.02 rows=997686 loops=1)
-> Hash Join (cost=6.49..105832.58 rows=997686 width=36) (actual
time=23.94..78411.62 rows=997686 loops=1)
-> Hash Join (cost=4.75..88371.34 rows=997686 width=32)
(actual time=15.68..63115.86 rows=997686 loops=1)
-> Hash Join (cost=3.69..68416.56 rows=997686
width=28) (actual time=12.56..45110.94 rows=997686 loops=1)
-> Hash Join (cost=2.58..50955.94 rows=997686
width=24) (actual time=9.24..23160.42 rows=997686 loops=1)
-> Seq Scan on sq_logfile sl
(cost=0.00..33493.86 rows=997686 width=20) (actual time=5.72..11518.14
rows=997686 loops=1)
-> Hash (cost=2.26..2.26 rows=126 width=4)
(actual time=3.46..3.46 rows=0 loops=1)
-> Seq Scan on sq_contenttypes ct
(cost=0.00..2.26 rows=126 width=4) (actual time=2.88..3.17 rows=126 loops=1)
-> Hash (cost=1.09..1.09 rows=9 width=4) (actual
time=3.21..3.21 rows=0 loops=1)
-> Seq Scan on sq_requestmethods rm
(cost=0.00..1.09 rows=9 width=4) (actual time=3.16..3.19 rows=9 loops=1)
-> Hash (cost=1.05..1.05 rows=5 width=4) (actual
time=3.06..3.06 rows=0 loops=1)
-> Seq Scan on sq_hierarchycodes hc
(cost=0.00..1.05 rows=5 width=4) (actual time=3.04..3.05 rows=5 loops=1)
-> Hash (cost=1.59..1.59 rows=59 width=4) (actual
time=8.20..8.20 rows=0 loops=1)
-> Seq Scan on sq_resultcodes rc (cost=0.00..1.59
rows=59 width=4) (actual time=7.93..8.07 rows=59 loops=1)
-> Hash (cost=1.93..1.93 rows=93 width=4) (actual
time=10.34..10.34 rows=0 loops=1)
-> Seq Scan on sq_clientaddrfqdn cafqdn (cost=0.00..1.93
rows=93 width=4) (actual time=9.92..10.13 rows=93 loops=1)
Total runtime: 99339.49 msec
-----Oorspronkelijk bericht-----
Van: Tomasz Myrta [mailto:jasiek@klaster.net]
Verzonden: vrijdag 19 september 2003 8:52
Aan: ries@jongert.nl
CC: pgsql-sql@postgresql.org
Onderwerp: Re: [SQL] is this explain good or bad???
> explain select count(*) from sq_logfile;
Not too helpful.
Better choice is:
explain analyze select * from sq_logfile;
Your explains show that selecting from view is 4 times slower than
selecting from a table (35988:128282). It is possible.
Anyway counting 1 million rows usualy takes a long time...
Regards,
Tomasz Myrta
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Cc: ries@jongert.nl
Subject: Re: is this explain good or bad???
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