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Re: query plan question

From: "David Parker" <dparker(at)tazznetworks(dot)com>
To: "Jeff" <threshar(at)torgo(dot)978(dot)org>
Cc: "Russell Smith" <mr-russ(at)pws(dot)com(dot)au>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: query plan question
Date: 2004-11-17 14:43:39
Message-ID: 07FDEE0ED7455A48AC42AC2070EDFF7C26B9AF@corpsrv2.tazznetworks.com (view raw or flat)
Thread:
Lists: pgsql-performance
I've got pg_autovacuum running on both platforms. I've verified that the
tables involved in the query have the same number of rows on both
databases.

I'm not sure where to look to see how the stats might be different. The
"good" database's pg_statistic table has 24 more rows than that in the
"bad" database, so there's definitely a difference. The good database's
pg_statistic has rows for 2 extra tables, but they are not tables
involved in the query in question...

So something must be up with stats, but can you tell me what the most
signicant columns in the pg_statistic table are for the planner making
its decision? I'm sure this has been discussed before, so if there's a
thread you can point me to, that would be great - I realize it's a big
general question.

Thanks for your time.

- DAP

>-----Original Message-----
>From: Jeff [mailto:threshar(at)torgo(dot)978(dot)org] 
>Sent: Wednesday, November 17, 2004 9:01 AM
>To: David Parker
>Cc: Russell Smith; pgsql-performance(at)postgresql(dot)org
>Subject: Re: [PERFORM] query plan question
>
>
>On Nov 17, 2004, at 7:32 AM, David Parker wrote:
>
>> Oh, I didn't realize that analyze gave that much more info. 
>I've got a 
>> lot to learn about this tuning stuff ;-)
>>
>> I've attached the output. I see from the new output where the slow 
>> query is taking its time (the nested loop at line 10), but I still 
>> have no idea why this plan is getting chosen....
>>
>
>looks like your stats are incorrect on the sparc.
>Did you forget to run vacuum analyze on it?
>
>also, do both db's have the same data loaded?
>there are some very different numbers in terms of actual rows floating 
>around there...
>
>--
>Jeff Trout <jeff(at)jefftrout(dot)com>
>http://www.jefftrout.com/
>http://www.stuarthamm.net/
>
>

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Subject: Re: query plan question
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