Thread: [DOCS] Prepare transaction doesn't mention NOTIFY

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/10/static/sql-prepare-transaction.html
Description:

Hi, in prepare transaction documentation in PG10 and earlier, it says that
you can't prepare a transaction with LISTEN or UNLISTEN but it doesn't
mention NOTIFY.

The NOTIFY documentation *does* mention that it won't work with PREPARE, so
it's just that the explicit mention of LISTEN and not NOTIFY is confusing.

I know this isn't the place to ask (and I'll never see the answer :) but I'm
baffled by the lack of support for NOTIFY in prepared transactions, and it's
causing me loads of grief, looks like I'm going to have to use a poll based
solution over a large number of databases, which is really unfortunate in
terms of resource utilisation.

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mark@inomial.com writes:
> Hi, in prepare transaction documentation in PG10 and earlier, it says that
> you can't prepare a transaction with LISTEN or UNLISTEN but it doesn't
> mention NOTIFY.

Yup, that's an oversight --- fixed.

> I know this isn't the place to ask (and I'll never see the answer :) but I'm
> baffled by the lack of support for NOTIFY in prepared transactions,

The big problem is that we can't do anything at PREPARE time to guarantee
that the NOTIFY will succeed.  Admittedly, the queue is large enough that
failure to insert the message isn't too likely, but "probably it will
work" is not the semantics we want from PREPARE.
        regards, tom lane


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