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Re: Writeable CTEs and empty relations

From: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>
To: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Writeable CTEs and empty relations
Date: 2010-02-09 22:49:07
Message-ID: 4B71E663.1020200@cs.helsinki.fi (view raw or flat)
Thread:
Lists: pgsql-hackers
On 2010-02-08 21:30 +0200, I wrote:
> This doesn't exactly work anymore since we modify the snapshot after
> calling ExecInitScan().  I'm not really familiar with this part of the
> code, so I'm asking: is there a simple enough way around this?  Would
> updating scan->rs_nblocks before scanning the first tuple be OK?

I've looked at this some more, and the problem is a lot bigger than I
originally thought.  We'd basically be forced to do another initscan()
before starting a new scan after the snapshot changed.  One way to
accomplish this would be that ExecutePlan() would leave a flag in EState
whenever the scan nodes need to reinit.

Does this sound completely unacceptable?


Regards,
Marko Tiikkaja

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