Re: "Constraint exclusion" is not general enough

From: Rod Taylor <pg(at)rbt(dot)ca>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Martin Lesser <ml-pgsql(at)bettercom(dot)de>
Subject: Re: "Constraint exclusion" is not general enough
Date: 2006-08-07 17:57:05
Message-ID: 1154973425.848.120.camel@home
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On Mon, 2006-08-07 at 13:44 -0400, Tom Lane wrote:
> Rod Taylor <pg(at)rbt(dot)ca> writes:
> > A simple way of doing this might be to use a minimum cost number?
>
> But you don't have any cost numbers until after you've done the plan.

Isn't it possible to find the cost using the straight forward (fast)
method, find out what order of magnitude it is in, then do a second pass
with additional planner bells and whistles turned on if the first plan
had a high estimate?

--

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