On 05/27/2015 09:40 AM, Glyn Astill wrote:
From: Andreas Joseph Krogh <andr...@visena.com>
To: pgsql-hackers@postgresql.org
Sent: Wednesday, 27 May 2015, 13:55
Subject: Re: [HACKERS] Triggers on transaction?
På onsdag 27. mai 2015 kl. 12:42:29, skrev Marko Tiikkaja <ma...@joh.to>:
On 5/27/15 12:39 PM, Jordan Gigov wrote:
I found myself in need of triggers that are run only once per transaction,
rather than per row or statement within the transaction. Meaning it will
always be deferred and never called twice for the same transaction.
What's the use case?
I've often needed this for stuff like:
UPDATE some_table SET col = 'foo' where id = 1;
UPDATE some_table SET col = 'bar' where id = 1;
I want the "on-tx"-trigger to only run once, and on the last update of "col" so
that it sees 'bar'.
I often have similar requirements, and usually end up having to track what's
already been updated with a trigger or similar then finally do the work in a
deferred trigger. I'd have thought something more like FOR EACH { ROW |
STATEMENT } PER TRANSACTION would be more fitting.
It's come up before. You can read some history here:
<http://postgresql.nabble.com/pre-commit-triggers-td5778575.html>
It seems clear there is some sort of unmet need here.
cheers
andrew
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