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Re: BUG #3826: Very Slow Execution of examplequery (wrong plan?)

From: Alexander Steffens <mail(at)a-st(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #3826: Very Slow Execution of examplequery (wrong plan?)
Date: 2009-04-16 12:22:46
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Lists: pgsql-bugs
Congratulations PostgreSQL-Team for your work!

with the current 8.4 B1 Version of PostgreSQL the bad execution time
of my example-Query containing a NOT EXISTS
changed from "aborted after hours" to just 5 seconds - double as quick
as my result with MS-SQL.

That's wonderful!

> insert into t1
> select distinct (t1.a + t2.a)*2
> from t1,t2
> where not exists (
>  select * from t1  tt where tt.a = (t1.a + t2.a)*2
> )

I assume there is now a hashed ANTI-SEMI-JOIN operator implemented?


Dipl.-Math. Alexander Steffens
Dorotheenstr. 16
23564 L├╝beck

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