Subject: Re: Another try at reducing repeated detoast work for
 PostGIS
From: Jeff Davis <pgsql@j-davis.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgreSQL.org
In-Reply-To: <4201.1250530640@sss.pgh.pa.us>
References: <4201.1250530640@sss.pgh.pa.us>
Content-Type: text/plain
Date: Mon, 17 Aug 2009 11:29:18 -0700
Message-Id: <1250533758.16514.12.camel@monkey-cat.sm.truviso.com>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

On Mon, 2009-08-17 at 13:37 -0400, Tom Lane wrote:
> Thinking about it again, it seems to me that a much narrower patch
> could solve the specific forms of the problem that the PostGIS folk
> are seeing.  Instead of trying to have a general-purpose method of
> preventing repeat de-toasting, we could just prevent it for inner
> indexscans by having ExecIndexEvalRuntimeKeys() detoast anything it's
> passing to the index AM. 

With this patch, are there still situations where we should be concerned
about repeated de-toasting, or does this solve the biggest part of the
problem?

If so, is it possible that two similar plans for the same query might
perform differently due to repeated de-toasting?

Regards,
	Jeff Davis