Thread: two concurrency questions

I searched the documentation and can't find the specific answers to
these questions.

1: Are user defined functions (eg pgplsql) atomic? I.e. if my function
updates a bunch of rows and one update fails for one reason or another
does it automatically roll-back to the state before the function was called?

2: If an update causes a trigger and the trigger updates a row and the
trigger fails, what happens? Is there a way to atomize the whole process?

Thanks,

Jeff Patterson
jpat@mpip.org
The Melanoma Patients' Information Page
http://www.mpip.org

Jeff Patterson <jpat@mpip.org> writes:

> I searched the documentation and can't find the specific answers to
> these questions.
>
> 1: Are user defined functions (eg pgplsql) atomic? I.e. if my function
> updates a bunch of rows and one update fails for one reason or another
> does it automatically roll-back to the state before the function was
> called?

Yes, because everything in PG is done inside a transaction, either
implicitly or explicitly.  If you have autocommit on and don't use
BEGIN/COMMIT, each statement is its own transaction.  Since a function
is always called from a statement, functions are atomic.

> 2: If an update causes a trigger and the trigger updates a row and the
> trigger fails, what happens? Is there a way to atomize the whole
> process?

See the answer to #1.

-Doug

On Mon, 2003-03-03 at 21:20, Jeff Patterson wrote:
> 1: Are user defined functions (eg pgplsql) atomic? I.e. if my function
> updates a bunch of rows and one update fails for one reason or another
> does it automatically roll-back to the state before the function was called?
>
> 2: If an update causes a trigger and the trigger updates a row and the
> trigger fails, what happens? Is there a way to atomize the whole process?

Both operations occur inside a transaction (if you don't explicitly
start a transaction, PostgreSQL does it for you), so they should both be
atomic: when an error occurs, the current transaction is aborted.

Cheers,

Neil
--
Neil Conway <neilc@samurai.com> || PGP Key ID: DB3C29FC