Date: Wed, 26 May 2010 19:16:20 +0100
From: Ben Morrow <ben@morrow.me.uk>
To: pgsql-sql@postgresql.org
Subject: Rules and sequences
Message-ID: <20100526181620.GA54996@osiris.mauzo.dyndns.org>
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I am trying to implement a fairly standard 'audit table' setup, but
using rules instead of triggers (since it should be more efficient).
However, I'm running into problems when one of the audited tables has a
'serial' column that is allowed to default:

    create table foo (id serial, bar text);
    create table audit (ix bigserial, rec text);
    create rule audit_insert as on insert to foo do also 
        insert into audit (rec) values ((new.*)::text);
    insert into foo (bar) values ('baz');
    select * from foo;
         id | bar 
        ----+-----
          1 | baz
        (1 row)
    select * from audit;
         ix |   rec   
        ----+---------
          1 | (2,baz)
        (1 row)

I can see why this is happening (the rule is essentially a macro, so the
NEW expression gets expanded twice, including the nextval call, so the
sequence is incremented twice), but is there any way to prevent it? Some
way of 'materialising' the NEW row so it is just plain values rather
than a list of expressions?

Ben