No, SELECT FOR UPDATE locks the rows matching the constraint and if no rows
match, none are locked.
as in (somewhat oracle syntax)
BEGIN
SELECT 'x' INTO a FROM test WHERE y = 10 FOR UPDATE;
UPDATE test SET z = 12;
EXCEPTION
WHEN no_data_found THEN
INSERT INTO test VALUES (10, 12);
END;
-----Original Message-----
From: Edward Q. Bridges [mailto:ed.bridges@buzznik.com]
Sent: den 12 december 2000 17:10
To: PostgreSQL general mailing list; Roger Wernersson
Subject: RE: [GENERAL] Re: Unanswered questions about Postgre
On Tue, 12 Dec 2000 12:04:46 +0100, Roger Wernersson wrote:
>
> I can't BEGIN - SELECT FOR UPDATE - INSERT or UPDATE - COMMIT as someone
> might insert after my SELECT and before my INSERT.
>
correct me if i'm wrong, but a select for update locks the table for
an insert or an update until the end of the transaction.
--e--
> Is there a right solution?
>
> /Roger
>
> -----Original Message-----
> From: Tim Kientzle [mailto:kientzle@acm.org]
> Sent: den 12 december 2000 02:10
> To: PostgreSQL general mailing list
> Subject: [GENERAL] Re: Unanswered questions about Postgre
>
>
> > Of course, people really shouldn't be inserting
> > objects which already exist, ...
>
> On the contrary, the best way to test if
> something already exists is to just try the
> INSERT and let the database tell you if
> it's already there. Both faster and more
> reliable than doing SELECT then INSERT.
>
> - Tim
>
