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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
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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                      
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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