From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jim C. Nasby <jnasby@pervasive.com>
Cc: PFC <lists@peufeu.com>
Cc: Mitchell Skinner <mitch@arctur.us>
Cc: pgsql-performance@postgresql.org
Cc: pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Big IN() clauses etc : feature proposal
Date: Wed, 10 May 2006 20:31:54 -0400
Message-ID: <22558.1147307514@sss.pgh.pa.us> (raw)
In-Reply-To: <20060510190011.GO99570@pervasive.com>
References: <op.s89zl30wcigqcu@apollo13>
<20060509105214.P90693@vesihiisi.cksoft.de>
<op.s8916gm6cigqcu@apollo13>
<20060509113337.M90693@vesihiisi.cksoft.de>
<op.s893vzcpcigqcu@apollo13>
<20060509103632.GD29652@svana.org>
<op.s897j60qcigqcu@apollo13>
<1147190285.32304.43.camel@firebolt>
<op.s9alu1vhcigqcu@apollo13>
<16680.1147201981@sss.pgh.pa.us>
<20060510190011.GO99570@pervasive.com>
"Jim C. Nasby" <jnasby@pervasive.com> writes:
> On Tue, May 09, 2006 at 03:13:01PM -0400, Tom Lane wrote:
>> PFC <lists@peufeu.com> writes:
>>> Fun thing is, the rowcount from a temp table (which is the problem here)
>>> should be available without ANALYZE ; as the temp table is not concurrent,
>>> it would be simple to inc/decrement a counter on INSERT/DELETE...
>>
>> No, because MVCC rules still apply.
> But can anything ever see more than one version of what's in the table?
Yes, because there can be more than one active snapshot within a single
transaction (think about volatile functions in particular).
> Speaking of which, if a temp table is defined as ON COMMIT DROP or
> DELETE ROWS, there shouldn't be any need to store xmin/xmax, only
> cmin/cmax, correct?
No; you forgot about subtransactions.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, jnasby@pervasive.com, lists@peufeu.com, mitch@arctur.us, pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Big IN() clauses etc : feature proposal
In-Reply-To: <22558.1147307514@sss.pgh.pa.us>
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