Re: DO with a large amount of statements get stuck with high memory consumption

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От Jan Wieck
Тема Re: DO with a large amount of statements get stuck with high memory consumption
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Msg-id CAGBW59dCR3cGEs68Cpe1F5hL+-2r8JPNTb1fDGf-M-jyKxJUUQ@mail.gmail.com
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Ответ на Re: DO with a large amount of statements get stuck with high memory consumption  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Mon, Jul 18, 2016 at 10:05 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Jan Wieck <jan@wi3ck.info> writes:
> In the meantime, would it be appropriate to backpatch the double linking
> of memory context children at this time? I believe it has had plenty of
> testing in the 9.6 cycle to be sure it didn't break anything.

I'm concerned about the ABI breakage risk from changing a data structure
as fundamental as MemoryContext.  Yeah, code outside utils/mmgr probably
*shouldn't* be looking at that struct, but that doesn't mean it isn't.
In the past we've generally only taken that sort of risk when there was
no other way to fix a bug; and this patch isn't a bug fix.  While this
does help performance in some corner cases, I don't think it's enough of
an across-the-board win to justify the risk of back-patching.

I would consider mucking with the linked lists of memory context children inside
of 3rd party code a really bad idea, but I concede. It isn't a bug fix and there is
that small risk that somebody did precisely that, so no backpatch.


Regards, Jan

--
Jan Wieck
Senior Postgres Architect

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