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Re: Transactions within a function body

From: "Bob Henkel" <bob(dot)henkel(at)gmail(dot)com>
To: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>
Cc: "Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com>, "PGSQL Hackers" <pgsql-hackers(at)postgresql(dot)org>, "Reg Me Please" <regmeplease(at)gmail(dot)com>, "Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at>, "Dennis Brakhane" <brakhane(at)googlemail(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: Transactions within a function body
Date: 2008-10-02 15:46:25
Message-ID: fedea56b0810020846x36211682h5b2c3d68ab9c1f58@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
Have you looked at creating a function in perl and creating a new
connection? Or using a dblink query which can create a new connection?
These two methods work. I have used them to insert to a log table regardless
of the parent transaction being commited or rolled back.

A old example I posted of using pl/perl can be found here ->
http://www.postgresqlforums.com/forums/viewtopic.php?f=4&t=647

The key is opening a new session which using dblink or pl/perl dbi
connection will do. This is not ideal or efficient.  It would be nice if you
could just do autonomous transactions natively in pl/pgsql, but I find this
method works for the cases where you need it(logging, huge batch processing
tasks where it's not ideal to process everything in one transaction).

Bob

"Hi all.
Is there a way to have (sub)transactions within a function body?
I'd like to execute some code (a transaction!) inside a function and later
decide whether that transaction is to be committed or not.
Thanks."

On Thu, Oct 2, 2008 at 10:40 AM, Alvaro Herrera
<alvherre(at)commandprompt(dot)com>wrote:

> Gurjeet Singh escribió:
>
> > I have seen this feature being asked for, and this work-around suggested
> so
> > many times. If plpgql does it internally, why not provide a clean
> interface
> > for this? Is there some road-block, or that nobody has ever tried it?
>
> Initially we aimed at just exposing SAVEPOINT and ROLLBACK TO in
> functions, but ran into the problem that the SPI stack needs to be dealt
> with appropriately and you can't do it if the user is able to modify it
> arbitrarily by calling transaction-modifying commands.  That's when the
> EXCEPTION idea came up.  We never went back and studied whether we could
> have fixed the SPI limitation, but it's not trivial.
>
> --
> Alvaro Herrera
> http://www.CommandPrompt.com/ <http://www.commandprompt.com/>
> The PostgreSQL Company - Command Prompt, Inc.
>
> --
> Sent via pgsql-general mailing list (pgsql-general(at)postgresql(dot)org)
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