Re: Query performance. 7.2.3 Vs. 7.3
От | Neil Conway |
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Тема | Re: Query performance. 7.2.3 Vs. 7.3 |
Дата | |
Msg-id | 1038537539.379.61.camel@tokyo обсуждение исходный текст |
Ответ на | Re: Query performance. 7.2.3 Vs. 7.3 (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: Query performance. 7.2.3 Vs. 7.3
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Список | pgsql-hackers |
On Thu, 2002-11-28 at 21:23, Tom Lane wrote: > wade <wade@wavefire.com> writes: > > Explain output can be found at http://arch.wavefire.com/72v73a.txt > > The difference evidently is that 7.3 chooses a mergejoin where 7.2 > picks a hashjoin. I was looking at this a bit in IRC, and I was more concerned by the fact that 7.3 was 20% than 7.2 on the same hardware, when they both used the same query plan (consider the data at the end of the URL above, after the execution of 'SET enable_mergejoin = off;'). Also, is it expected that the cardinality estimates for join steps won't be very accurate, right? (estimated: 19 rows, actual: 765 rows) Cheers, Neil -- Neil Conway <neilc@samurai.com> || PGP Key ID: DB3C29FC
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