Ð ÐÑÑ, 17.08.2004, Ð 16:12, Bruno Wolff III ÐÐÑÐÑ:
> > SELECT MAX(position) FROM (SELECT position FROM classes WHERE name =
> > 'foo' FOR UPDATE OF classes) AS foo
> >
> > It's clear which rows should be locked here, I think.
>
> Even if it was allowed, it probably wouldn't be good enough because it won't
> protect against newly inserted records.
Can you detail an example where this wouldn't be good enough?
In a PL/pgSQL function I'm doing
PERFORM position FROM class_fields WHERE class = arg_class_name;
INSERT INTO class_fields (class, field, position) VALUES
(arg_class_name, arg_field_name, (SELECT MAX(position) FROM class_fields
WHERE class = arg_class_name));
Is this unsafe?
The question initially arose because I wanted to do something similar to
SELECT INTO var_new_position MAX(position) FROM class_fields WHERE class
= arg_class_name FOR UPDATE OF class_fields;
which didn't work.
Thanks
--
Markus Bertheau <[EMAIL PROTECTED]>
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