From: Tom Lane <tgl@sss.pgh.pa.us>
To: Markus Schaber <schabi@logix-tt.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: merge>hash>loop
Date: Tue, 18 Apr 2006 19:38:33 -0400
Message-ID: <20064.1145403513@sss.pgh.pa.us> (raw)
In-Reply-To: <4444C4CF.2000106@logix-tt.com>
References: <1145029009.3422.31.camel@spectre.intellivid.com>
<10000.1145031205@sss.pgh.pa.us>
<1145033149.3422.41.camel@spectre.intellivid.com>
<11035.1145033929@sss.pgh.pa.us>
<4444C4CF.2000106@logix-tt.com>
Markus Schaber <schabi@logix-tt.com> writes:
> An easy first approach would be to add a user tunable cache probability
> value to each index (and possibly table) between 0 and 1. Then simply
> multiply random_page_cost with (1-that value) for each scan.
That's not the way you'd need to use it. But on reflection I do think
there's some merit in a "cache probability" parameter, ranging from zero
(giving current planner behavior) to one (causing the planner to assume
everything is already in cache from prior queries). We'd have to look
at exactly how such an assumption should affect the cost equations ...
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, schabi@logix-tt.com
Subject: Re: merge>hash>loop
In-Reply-To: <20064.1145403513@sss.pgh.pa.us>
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