Re: index scan on =, but not < ? - Mailing list pgsql-performance

From Manfred Koizar
Subject Re: index scan on =, but not < ?
Date
Msg-id 3oei31lc0uitgvmgfbsehm4r92ad9reas3@email.aon.at
Whole thread Raw
In response to Re: index scan on =, but not < ?  (David Brown <time@bigpond.net.au>)
List pgsql-performance
On Thu, 10 Mar 2005 10:24:46 +1000, David Brown <time@bigpond.net.au>
wrote:
>What concerns me is that this all depends on the correlation factor, and
>I suspect that the planner is not giving enough weight to this.

The planner does the right thing for correlations very close to 1 (and
-1) and for correlations near zero.  For correlations somewhere between
0 and 1 the cost is estimated by interpolation, but it tends too much
towards the bad end, IMHO.

Servus
 Manfred

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