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Re: wCTE: why not finish sub-updates at the end, not the beginning?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: wCTE: why not finish sub-updates at the end, not the beginning?
Date: 2011-02-26 16:10:33
Message-ID: 19003.1298736633@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Greg Stark <gsstark(at)mit(dot)edu> writes:
> On Sat, Feb 26, 2011 at 5:55 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> So we really need some refactoring here. I dislike adding another
>> fundamental step to the ExecutorStart/ExecutorRun/ExecutorEnd sequence,
>> but there may not be a better way. The only way I see to fix this
>> without changing that API is to have ExecutorRun do the cleanup
>> processing just after the top plan node returns a null tuple, and that
>> seems a bit ugly as well.

> How would that handle the case of a cursor which isn't read to
> completion? Should it still execute the CTEs to completion?

Right at the moment we dodge that issue by disallowing wCTEs in cursors.
If we did allow them, then I would say that the wCTEs have to be run to
completion when the cursor is closed.

			regards, tom lane

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