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Re: Append Cost in query planners

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Nimesh Satam <nimesh(dot)zedo(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org, nimesh(at)zedo(dot)com
Subject: Re: Append Cost in query planners
Date: 2007-10-28 15:38:15
Message-ID: 4724ACE7.4090401@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-performance
Nimesh Satam wrote:
> We are trying to implement partition on one tables on date basis. the
> overall cost and timming and cost of the query is increasing on the Append
> of the child table output. As shown below:
> 
> *->  Append  (cost=0.00..112217.92 rows=2752906 width=52) (actual time=
> 2454.207..20712.021 rows=2752905 loops=1)
>  ->  Seq Scan on trm  (cost=0.00..28570.35 rows=1 width=52) (actual time=
> 2423.374..2423.374 rows=0 loops=1)
>   Filter: ((sqldate >= '2007-06-01 00:00:00'::timestamp without time zone)
> AND (sqldate <= '2007-06-03 00:00:00'::timestamp without time zone))
>  ->  Seq Scan on trm_d20070601 trm  (cost=0.00..29203.41 rows=961094
> width=52) (actual time=30.825..3027.217 rows=961094 loops=1)
>   Filter: ((sqldate >= '2007-06-01 00:00:00'::timestamp without time zone)
> AND (sqldate <= '2007-06-03 00:00:00'::timestamp without time zone))
>  ->  Seq Scan on trm_d20070602 trm  (cost=0.00..27442.52 rows=903168
> width=52) (actual time=11.142..2687.422 rows=903168 loops=1)
>   Filter: ((sqldate >= '2007-06-01 00:00:00'::timestamp without time zone)
> AND (sqldate <= '2007-06-03 00:00:00'::timestamp without time zone))
>  ->  Seq Scan on trm_d20070603 trm  (cost=0.00..27001.64 rows=888643
> width=52) (actual time=13.697..2568.012 rows=888643 loops=1)
>   Filter: ((sqldate >= '2007-06-01 00:00:00'::timestamp without time zone)
> AND (sqldate <= '2007-06-03 00:00:00'::timestamp without time zone))*
> 
> Can someone let me know, how we can reduce the overall cost and time of the
> append operation, and what parameters in the confirguration needs to be
> changed?

Does the query really return almost 3 million rows? If that's the case,
I'm afraid there isn't much you can do, software-wise. If not, show us
the complete query and EXPLAIN ANALYZE output.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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Next:From: Tom LaneDate: 2007-10-28 16:53:59
Subject: Re: partitioned table and ORDER BY indexed_field DESCLIMIT 1
Previous:From: Nimesh SatamDate: 2007-10-28 15:22:53
Subject: Append Cost in query planners

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