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Re: enable_joinremoval

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>,Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: enable_joinremoval
Date: 2010-03-29 14:42:19
Message-ID: 20100329144219.GA3925@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane escribió:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Mon, Mar 29, 2010 at 4:33 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> >> So I think we need a parameter for join removal also.
> 
> > I had this in my original patch but Tom wanted it taken out.
> 
> And I still don't want it.  We are NOT going in the direction of adding
> an enable_ knob for every single planner activity --- do you have the
> faintest idea how many there would be?  We have such knobs for a small
> number of cases where it's arguable that the action might be the wrong
> thing for a particular query.  Join removal, if applicable, can't
> possibly be the wrong choice; it's better than every other join strategy.

It seems that what's really needed is some debug output to be able to
find out what it did.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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