Re: Query using SeqScan instead of IndexScan - Mailing list pgsql-performance

From Josh Berkus
Subject Re: Query using SeqScan instead of IndexScan
Date
Msg-id 200604021530.55251.josh@agliodbs.com
Whole thread Raw
In response to Query using SeqScan instead of IndexScan  (Brendan Duddridge <brendan@clickspace.com>)
Responses Re: Query using SeqScan instead of IndexScan  (Brendan Duddridge <brendan@clickspace.com>)
Re: Query using SeqScan instead of IndexScan  (Jim Nasby <jnasby@pervasive.com>)
List pgsql-performance
Brendan,

> But just as a follow up question to your #1 suggestion, I have 8 GB
> of ram in my production server. You're saying to set the
> effective_cache_size then to 5 GB roughly? Somewhere around 655360?
> Currently it is set to 65535. Is that something that's OS dependent?
> I'm not sure how much memory my server sets aside for disk caching.

Yes, about.  It's really a judgement call; you're looking for the approximate
combined RAM available for disk caching and shared mem.  However, this is
just used as a way of estimating the probability that the data you want is
cached in memory, so you're just trying to be order-of-magnitude accurate,
not to-the-MB accurate.

--
Josh Berkus
Aglio Database Solutions
San Francisco

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