On Tue, Jul 5, 2011 at 2:42 PM, John Fabiani <jo...@jfcomputer.com> wrote:
> On Tuesday, July 05, 2011 01:11:11 pm Kevin Crain wrote: > > You don't need a loop there. Assuming your order id field is of type > > varchar you can just build the first part of your string and then do a > > count to get the last part using a LIKE comparison: > > > > select count(id_order) + 1 from sometable WHERE id_order LIKE > 'O-20110704 > > -%'; > > > > If you do this inside a function it will be like running it in a > > transaction so you shouldn't have to worry about it being a multi-user > > system. > > > > > > > > I like this - looks better than what I'm currently doing. Thanks > Johnf > > It is simpler, but it will result in id collision if two inserts runs at the same time, particularly if the count query takes a while to run, so be prepared to handle that. Make sure you have an index which can satisfy that count query quickly. If you are not using the C locale for your database, that means you must create an index on that column that uses text_pattern_ops or varchar_pattern_ops (depending on if it is text or varchar column) so that postgresql can use the index for that comparison, otherwise LIKE clauses will force a sequential scan of the whole table every time. C locale does byte by byte text comparison, so the special index isn't required. http://www.postgresql.org/docs/9.0/interactive/indexes-opclass.html
