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Re: RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1 - Mailing list pgsql-performance

From Tom Lane
Subject Re: RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1
Date
Msg-id 1583.1367858328@sss.pgh.pa.us
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In response to RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1  (Christoph Berg <christoph.berg@credativ.de>)
Responses Re: RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1  (Christoph Berg <cb@df7cb.de>)
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Christoph Berg <christoph.berg@credativ.de> writes:
> We recently (finally) migrated an Request Tracker 3.4 database running
> on 8.1.19 to 9.2.4. The queries used by rt3.4 are sometimes weird, but
> 8.1 coped without too much tuning. The schema looks like this:

The newer rowcount estimates are much further away from reality:

>  Unique  (cost=1117.67..1118.46 rows=9 width=1115) (actual time=82.646..85.695 rows=439 loops=1)

>  Unique  (cost=784205.94..796940.08 rows=145533 width=1061) (actual time=9710.683..9713.175 rows=439 loops=1)

Has the new DB been analyzed?  Maybe you had custom stats targets in
the old DB that didn't get copied to the new one?

            regards, tom lane

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