Re: Double sequence increase on single insert with RULE on

Is that safe or could lastval return the value of a previous insert if
an insert fails? Though I suppose if the insert fails then the rule
shouldn't get fired...

On Thu, Nov 17, 2005 at 10:11:29AM +0200, Sarunas Krisciukaitis wrote:
> Ok :) Then I found the solution in this partical case:
> CREATE RULE test1_on_insert AS ON INSERT TO test1 DO INSERT INTO
> test_log1 (qid) VALUES ( (SELECT lastval()) );
> With this rule all inserts are working as expected :)
>
> Thank you for you advise :)
>
> Sarunas
>
> Michael Fuhr wrote:
>
> >On Wed, Nov 16, 2005 at 10:31:10AM +0200, Sarunas Krisciukaitis wrote:
> >
> >
> >>I understand that RULES are like macros.
> >>Strangest thing here is that INSERT to test1 will touch only one
> >>sequence: test1_id_seq.
> >>And it increments test1_id_seq twice during insert with RULE.
> >>
> >>
> >
> >Yes, that's a well-known effect of rewriting a query that includes
> >a call to nextval().  NEW.id in the rule doesn't refer to the value
> >that's inserted, but rather to the expression that's evaluated to
> >get that value.  Since you didn't provide a value for id it gets
> >the default: nextval('test1_id_seq').  That expression is used in
> >both inserts, so the sequence gets incremented twice.  See the
> >archives for numerous past discussions of this behavior.
> >
> >
> >
>
>
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