Hi Tom!
> > BEGIN
> > INSERT
> > OR UPDATE
> > INSERT
> > OR UPDATE
> > COMMIT
> >
> > Suppose the second INSERT fails with a duplicate key, we cannot do the
> > update (or get the previous INSERT) because the ROLLBACK is mandatory.
>
> No it isn't. You say SAVEPOINT, then do the INSERT, then say either
> RELEASE SAVEPOINT if the insert succeeded, or ROLLBACK TO SAVEPOINT
> if the insert failed. (RELEASE is actually optional here, but might
> make things a bit more transparent.) Then you go on with your
> transaction.
I tried what you suggested, and here are the results:
xyz=> TRUNCATE TABLE t1;
TRUNCATE TABLE
xyz=> BEGIN;
BEGIN
xyz=> SAVEPOINT p1;
SAVEPOINT
xyz=> INSERT INTO t1 VALUES ('w', 1);
INSERT 0 1
xyz=> RELEASE SAVEPOINT p1;
RELEASE
xyz=> SELECT * FROM t1;
c1 | n1
----+----
w | 1
(1 row)
xyz=> SAVEPOINT p2;
SAVEPOINT
xyz=> INSERT INTO t1 VALUES ('w', 1);
ERROR: duplicate key violates unique constraint "t1_c1_idx"
xyz=> END;
ROLLBACK
xyz=> SELECT * FROM t1;
c1 | n1
----+----
(0 rows)
xyz=>
> The problem is that you are using transaction-ending
> commands where you should be using savepoint-ending commands.
As far as I know, transaction-ending commands are ROLLBACK, ABORT, and
COMMIT. I do not know of any others, and I have no idea what you mean about
savepoint-ending. Please explain.
--
Regards,
Richard Kut
Database Administrator
Research & Development
Intelerad Medical Systems Inc.
460 Ste-Catherine West, Suite 210
Montreal, Quebec, Canada H3B 1A7
Tel: 514.931.6222 x7733
Fax: 514.931.4653
rkut@intelerad.com
www.intelerad.com
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