Re: [PATCH] V3: Idle in transaction cancellation

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От Robert Haas
Тема Re: [PATCH] V3: Idle in transaction cancellation
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Msg-id AANLkTi=du2m-k_Y4MU27Q83Ln7UN8VzZS8x4rakXosrd@mail.gmail.com
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Ответ на Re: [PATCH] V3: Idle in transaction cancellation  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: [PATCH] V3: Idle in transaction cancellation  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Thu, Dec 16, 2010 at 3:18 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> Hmm.  It's seeming to me that what we want to do is something like this:
>
>> 1. If an error is thrown while DoingCommandRead, it gets upgraded to
>> FATAL.  I don't think we have much choice about this because, per your
>> previous comments, we can't longjmp() here without risking protocol
>> breakage, and we certainly can't return from an elog(ERROR) or
>> ereport(ERROR).
>
> Um, if that's the ground rules then we have no advance over the current
> situation.
>
> I guess you misunderstood what I said.  What I meant was that we cannot
> longjmp *out to the outer level*, ie we cannot take control away from
> the input stack.  We could however have a TRY block inside the interrupt
> handler that catches and handles (queues) any errors occurring during
> transaction abort.  As long as we eventually return control to openssl
> I think it should work.

Is there any real advantage to that?  How often do we hit an error
trying to abort a transaction?  And how will we report the error
anyway?  I thought the next thing we'd report would be the recovery
conflict, not any bizarre can't-abort-the-transaction scenario.

> (Hm, but I wonder whether there are any hard
> timing constraints in the ssl protocol ... although hopefully xact abort
> won't ever take long enough that that's a real problem.)

That would be incredibly broken.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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