To: Robert Haas <robertmhaas@gmail.com>
cc: Jim Nasby <decibel@decibel.org>, Greg Sabino Mullane <greg@turnstep.com>,
	pgsql-hackers@postgresql.org
Subject: Re: global temporary tables 
In-reply-to: <y2u603c8f071004241814x10e29bc8pb46cad5edc0e2a5b@mail.gmail.com> 
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	<7796.1272125493@sss.pgh.pa.us>
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	<9319.1272130283@sss.pgh.pa.us>
	<FD5C55A5-5003-4C4E-8DC6-E124A13E0B68@decibel.org>
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Sat, 24 Apr 2010 21:14:44 -0400"
Date: Sat, 24 Apr 2010 21:37:31 -0400
Message-ID: <18126.1272159451@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Robert Haas <robertmhaas@gmail.com> writes:
> Unfortunately, I don't see much alternative to making smgr know
> something about the temp-ness of the relation, though I'm hoping to
> keep the smgr surgery to an absolute minimum.  Maybe what we could do
> is incorporate the backend ID or PID into the file name when the
> relation is temp.  Then we could scan for and nuke such files pretty
> easily.  Otherwise I can't really think how to make it work.

I think that could be a really good idea, mainly because it makes
post-crash cleanup MUCH safer: you can tell with certainty from the
filename that it's a leftover temp table.  The notion of zapping files
just because we don't see them listed in pg_class has always scared the
heck out of me.

We already know temp-ness at pretty low levels, like bufmgr vs localbuf.
Pushing it all the way down to smgr doesn't seem like a leap; in fact
I think it would eliminate a separate isTemp parameter in a lot of places.

			regards, tom lane