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Re: Writeable CTEs and empty relations

From: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Writeable CTEs and empty relations
Date: 2010-02-09 05:32:44
Message-ID: 4B70F37C.2000808@cs.helsinki.fi (view raw or flat)
Thread:
Lists: pgsql-hackers
On 2010-02-09 01:09 +0200, Tom Lane wrote:
> Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> writes:
>> I traced this down to heapam.c, which has this:
>> ...
>> This doesn't exactly work anymore since we modify the snapshot after
>> calling ExecInitScan().
> 
> So don't do that.  The executor is generally entitled to assume that
> parameters given to ExecutorStart are correct.  In particular, changing
> the snapshot after the query has started to run seems to me to ensure
> all sorts of inconsistent and undesirable behavior.

You do remember that the whole patch in its current form depends on
modifying the snapshot?


Regards,
Marko Tiikkaja

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