Re: Question on triggers and plpgsql

On Fri, Apr 08, 2005 at 10:36:26AM -0400, Tom Lane wrote:

> AFAICS the only way that you could get into a can't-roll-back situation
> is if the trigger tries to propagate the update outside the database.
> For instance, the proverbial trigger to send mail: once sent you can't
> cancel it. But really this is dangerous even in an AFTER trigger ---
> the transaction could still be rolled back after the AFTER trigger
> fires.

People who know more about this will no doubt correct me, but isn't
such a case crying out for LISTEN/NOTIFY instead? That is, your
trigger puts the mail content into a table of mails to be sent, and
wakes up the mail-sender client with the NOTIFY; the NOTIFY and the
commit to the mail-it table only happen in that case if the
transaction commits. And since mail is async anyway, the extra few
seconds shouldn't make any difference, right?

A

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