From: | Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Writeable CTEs and empty relations |
Date: | 2010-02-10 22:50:48 |
Message-ID: | 4B733848.3000107@cs.helsinki.fi |
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Lists: | pgsql-hackers |
On 2010-02-10 23:57 +0200, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> If the executor has buried in it the assumption that the snapshot
>> can't change after startup, then does that mean that we need to start
>> up and shut down the executor for each subquery?
>
> Yes, I think so. That's the way it's always worked in the past;
> see for example PortalRunMulti() and ProcessQuery(). I think trying
> to change that is a high-risk, low-reward activity.
>
> This probably means that the planner output for queries involving
> writeable CTEs has to be a separate PlannedStmt per such CTE.
I'm looking at this, but I can't think of any good way of associating
the tuplestores from PortalRunMulti() with the correct CTEs. Any ideas?
Regards,
Marko Tiikkaja
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