From: Robert Creager <Robert_Creager@LogicalChaos.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Fuhr <mike@fuhr.org>
Cc: PGPerformance <pgsql-performance@postgresql.org>
Subject: Re: Index isn't used during a join.
Date: Wed, 11 Jan 2006 21:20:46 -0700
Message-ID: <20060111212046.200f3e55@thunder.logicalchaos.org> (raw)
In-Reply-To: <12877.1136993583@sss.pgh.pa.us>
References: <20060109212338.6420af12@thunder.logicalchaos.org>
<20060110055818.GA55076@winnie.fuhr.org>
<20060110221055.053596ab@thunder.logicalchaos.org>
<20060111075655.GA51292@winnie.fuhr.org>
<20060111072659.7c1772ad@thunder.logicalchaos.org>
<12877.1136993583@sss.pgh.pa.us>
When grilled further on (Wed, 11 Jan 2006 10:33:03 -0500),
Tom Lane <tgl@sss.pgh.pa.us> confessed:
> The planner understands about transitivity of equality, ie given a = b
> and b = c it can infer a = c. It doesn't do any such thing for
> inequalities though, nor does it deduce f(a) = f(b) for arbitrary
> functions f. The addition Michael suggested requires much more
> understanding of the properties of the functions in your query than
> I think would be reasonable to put into the planner.
>
OK. I think reached a point that I need to re-organize how the data is stored,
maybe ridding myself of the schema and switching entirely to views. At that
point, I likely could rid myself of the function (unmunge_time) I'm using, and
work with times and doy fields.
Thanks,
Rob
--
21:17:00 up 4 days, 13:43, 9 users, load average: 2.02, 2.18, 2.23
Linux 2.6.12-12-2 #4 SMP Tue Jan 3 19:56:19 MST 2006
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To: pgsql-performance@postgresql.org
Cc: Robert_Creager@LogicalChaos.org, tgl@sss.pgh.pa.us, mike@fuhr.org
Subject: Re: Index isn't used during a join.
In-Reply-To: <20060111212046.200f3e55@thunder.logicalchaos.org>
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