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Re: Writeable CTEs and empty relations

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Writeable CTEs and empty relations
Date: 2010-02-10 21:57:51
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Lists: pgsql-hackers
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.

			regards, tom lane

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