annotate demo/broadcast.ur @ 704:70cbdcf5989b

UNIQUE constraints
author Adam Chlipala <adamc@hcoop.net>
date Tue, 07 Apr 2009 12:24:31 -0400
parents 4e260887d8f2
children 1a317a707d71
rev   line source
adamc@699 1 functor Make(M : sig type t end) = struct
adamc@699 2 sequence s
adamc@699 3 table t : {Id : int, Client : client, Channel : channel M.t}
adamc@699 4
adamc@699 5 type topic = int
adamc@699 6
adamc@699 7 val inj : sql_injectable topic = _
adamc@699 8
adamc@699 9 val create = nextval s
adamc@699 10
adamc@699 11 fun subscribe id =
adamc@699 12 cli <- self;
adamc@699 13 ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[cli]});
adamc@699 14 case ro of
adamc@699 15 None =>
adamc@699 16 ch <- channel;
adamc@699 17 dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[cli]}, {[ch]}));
adamc@699 18 return ch
adamc@699 19 | Some r => return r.T.Channel
adamc@699 20
adamc@699 21 fun send id msg =
adamc@699 22 queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]})
adamc@699 23 (fn r => Basis.send r.T.Channel msg)
adamc@699 24
adamc@699 25 fun subscribers id =
adamc@699 26 r <- oneRow (SELECT COUNT( * ) AS N FROM t WHERE t.Id = {[id]});
adamc@699 27 return r.N
adamc@699 28 end