Re: many 'OR' in WHERE-condition - Mailing list pgsql-sql

From A. Kretschmer
Subject Re: many 'OR' in WHERE-condition
Date
Msg-id 20070420122016.GF15322@a-kretschmer.de
Whole thread Raw
In response to Re: many 'OR' in WHERE-condition  (Richard Huxton <dev@archonet.com>)
List pgsql-sql
am  Fri, dem 20.04.2007, um 12:59:01 +0100 mailte Richard Huxton folgendes:
> A. Kretschmer wrote:
> >
> >It's not my problem - i found it in a forum (german)
> >http://pg-forum.de/showthread.php?t=1332
> >
> >If the list contains up to 195 entrys -> up to 195 bitmap index scans
> >and BitmapOr -> 7.839ms
> >
> >If the list contains 196 entrys -> seq-scan -> 5591.567ms
> 
> It looks like it's getting the row estimate badly wrong.
> 
> "Seq Scan on t_datasets_searchindices_rel  (cost=0.00..129053.50 
> rows=159277 width=4) (actual time=0.213..5590.435 rows=325 loops=1)

Uh oh, i have overlook this.


> 
> Probably worth increasing the statistics estimate for that column (ALTER 
> TABLE ... ALTER COLUMN ... SET STATISTICS=N)

Thx for your hints!


Andreas
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Andreas Kretschmer
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