"Mark J. Bobak" wrote:
>
> Um, no. Select for update will lock whatever rows it selects. If it
> happens to select all the rows in a table, then all the rows in the
> table will be locked. But, you could select for update where
> primary_key=1 and select (and lock) just one row. As with other DML
> locks, the lock will be released when you commit or rollback.
>
> See the concepts manual for more details.
>
> Hope that helps,
>
> -Mark
>
> On Fri, 2002-09-27 at 20:33, tony ynot wrote:
> > Is Select ... For Update;
> > a cheap table lock?
> > It seems whenever code uses this statement
> > all the records in the cursor are locked
> > until the cursor is closed.
> >
IMHO SELECT .. FOR UPDATE is something which, in most cases where I see
it used, is perfectly dispensable. It's a relic of Oracle 5 when there
was no real row lock (only exclusive table locks and 'intent' row locks)
and the difficulty was to hold them for as short a period as possible -
hence SELECT ... FOR UPDATE to get the rowid, then a very fast UPDATE
using the rowid and commit. Since Oracle6, unless you intend to
'reserve' a row, run a 3 hours process and be certain to find the same
value when you're done, you can directly execute the update, it will
spare you a select.
--
Regards,
Stephane Faroult
Oriole Software
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Stephane Faroult
INET: sfaroult_at_oriole.com
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Received on Sat Sep 28 2002 - 07:13:19 CDT
