On Tue, Nov 22, 2011 at 12:48 PM, David Johnston <polobo@xxxxxxxxx> wrote: > -----Original Message----- > From: pgsql-general-owner@xxxxxxxxxxxxxx > [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of Kenneth Tilton > Sent: Tuesday, November 22, 2011 12:26 PM > To: pgsql-general@xxxxxxxxxxxxxx > Subject: possible race condition in trigger functions on insert > operations? > > Bit of a trigger NOOB Q: > > I am trying to use a trigger function to automatically populate new rows in > a table with a public ID of the form YYYY-NNN such that the 42nd row > created in 2011 would get the ID "2011-042". Each row is associated via an > iasid column with a row in an audit table that has a timestamp column called > created. This works OK, but I am worried about two rows getting the same > case_no if they come in at the same time (whatever that means): > > declare > case_yr integer; > yr_case_count bigint; > begin > select date_part('year', created) into case_yr > from audit > where audit.sid = NEW.iasid; > > select count(*) into yr_case_count > from fwa_case, audit > where fwa_case.iasid=audit.sid > and date_part('year', created) = case_yr; > > NEW.case_no = to_char( case_yr, '9999' ) || '-' || > to_char(1+yr_case_count, 'FM000'); > return NEW; > end; > > Do I have to worry about this, or does ACID bail me out? If the former, what > do I do? I am thinking first put a uniqueness constraint on the column and > then figure out how to do retries in a trigger function. > > kenneth > -------------------------------------------------------- > > Why can't you just use a sequence? The sequence has to be within the year. Someone suggested a cron job to reset the sequence at the beginning of the year but I find that alternative unappealing for some reason. -kt -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
