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Re: WIP Join Removal

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, List pgsql-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: WIP Join Removal
Date: 2008-09-02 15:35:36
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Lists: pgsql-patches
Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Mon, 2008-09-01 at 22:23 +0300, Heikki Linnakangas wrote:
>> Did plan invalidation make it safe to rely on the presence of a unique 
>> index for planning decisions?

> My understanding was "Yes" and this case was the specific reason I
> originally wanted to pursue plan invalidation back in 2006.

Yeah, it should work.  The theory is that any schema change that could
affect planning should result in broadcasting a relcache inval message
for the table (not just the index, note).  I'm pretty confident that
that works for index addition and removal (cf index_update_stats and
index_drop).  There might be some situations where we need to force a
relcache inval but don't currently do so --- constraint addition/removal
for instance I'm not too sure about.  But that would represent an easily
fixable bug.

			regards, tom lane

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