> On Thu, Sep 8, 2011 at 1:22 PM, Merlin Moncure <mmoncure@xxxxxxxxx> wrote: >> >> On Thu, Sep 8, 2011 at 4:01 AM, Eduardo Piombino <drakorg@xxxxxxxxx> >> wrote: >> > Hi, would it be possible to implement a nowait modifier to the update >> > statement in order to tell it not to wait and raise an error -just like >> > a >> > select for update nowait would-, instead of defaulting to waiting >> > forever >> > until the lock becomes available? >> > >> > The lack of such a modifier nowadays forces me to do a select for update >> > before every update on which I need the fastest response possible, and >> > it >> > would be great if it could be integrated into the command itself. >> > >> > Just an idea. >> >> +1 >> >> note you may be able to emulate this by sneaking a nolock into the >> update statement in a highly circuitous fashion with something like: >> update foo set v = 2 from (select 1 from foo where id = 1 for update >> nowait) q where id = 1; On Thu, Sep 8, 2011 at 3:33 PM, Eduardo Piombino <drakorg@xxxxxxxxx> wrote: > Nice. > Much more maintainable IMO and quite close to what I was looking for. > Thanks a lot for the suggestion, I will definitely try it/implement it right > away. > Still has some redundancy compared to an hypothetical nowait modifier but I > think it's the very best alternative so far. > > Eduardo Thanks -- in hindsight though I think it's better to write it this way: explain update foo set v = 2 from ( select id from foo where id = 1 for update nowait ) q where q.id = foo.id; another interesting way to write it that is 9.1 only is like this: with x as ( select id from foo where id = 1 for update nowait ) update foo set v = 2 where exists (select 1 from x where x.id = foo.id); which gives approximately the same plan. merlin -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
