Re: count * performance issue

am Thu, dem 06.03.2008, um 12:36:48 +0530 mailte sathiya psql folgendes:
>
> QUERY PLAN
> ------------------------------------------------------------------------------------------------------------------------------
> Aggregate (cost=205756.95..205756.95 rows=1 width=0) (actual time=
> 114675.042..114675.042 rows=1 loops=1)
> -> Seq Scan on call_log (cost=0.00..193224.16 rows=5013112 width=0)
> (actual time=11.754..91429.594 rows=5061619 loops=1)
> Filter: (call_id > 0)
> Total runtime: 114699.797 ms
> (4 rows)

'call_id > 0' are your where-condition? An INDEX can't help, all rows
with call_id > 0 are in the result, and i guess, that's all records in
the table.

>
>
> it is now taking 114 seconds, i think because of load in my system.... any way
> will you explain., what is this COST, actual time and other stuffs....

08:16 < akretschmer> ??explain
08:16 < rtfm_please> For information about explain
08:16 < rtfm_please> see http://explain-analyze.info
08:16 < rtfm_please> or http://www.depesz.com/index.php/2007/08/06/better-explain-analyze/
08:16 < rtfm_please> or http://www.postgresql.org/docs/current/static/sql-explain.html

and

http://redivi.com/~bob/oscon2005_pgsql_pdf/OSCON_Explaining_Explain_Public.pdf

Read this to learn more about explain.

Andreas
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Andreas Kretschmer
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