From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
Cc: | "Ed L(dot)" <pgsql(at)bluepolka(dot)net>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Why won't it index scan? |
Date: | 2006-05-22 22:43:22 |
Message-ID: | 15660.1148337802@sss.pgh.pa.us |
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Lists: | pgsql-general |
"Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:
> On Wed, May 17, 2006 at 10:29:14PM -0400, Tom Lane wrote:
>> The reason the default is currently 10 is just conservatism: it was
>> already an order of magnitude better than what it replaced (a *single*
>> representative value) and I didn't feel I had the evidence to justify
>> higher values. It's become clear that the default ought to be higher,
>> but I've still got no good fix on a more reasonable default. 100 might
>> be too much, or then again maybe not.
> Is the only downside to a large value planning speed? It seems it would
> be hard to bloat that too much, except in cases where people are
> striving for millisecond response times, and those folks had better know
> enough about tuning to be able to adjust the stats target...
It would be nice to have some *evidence*, not unsupported handwaving.
regards, tom lane
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