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comparison lib/ur/top.ur @ 683:9a2c18dab11d

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Expunging non-nullable rows
author Adam Chlipala <adamc@hcoop.net>
date Sun, 29 Mar 2009 13:30:01 -0400
parents 5bbb542243e8
children 4e260887d8f2
comparison
equal deleted inserted replaced
682:5bbb542243e8 683:9a2c18dab11d
198 | Some _ => sql_binary sql_eq e1 (sql_inject e2) 198 | Some _ => sql_binary sql_eq e1 (sql_inject e2)
199 199
200 200
201 functor Broadcast(M : sig type t end) = struct 201 functor Broadcast(M : sig type t end) = struct
202 sequence s 202 sequence s
203 table t : {Id : int, Client : option client, Channel : option (channel M.t)} 203 table t : {Id : int, Client : client, Channel : channel M.t}
204 204
205 type topic = int 205 type topic = int
206 206
207 val inj : sql_injectable topic = _ 207 val inj : sql_injectable topic = _
208 208
209 val create = nextval s 209 val create = nextval s
210
211 val cleanup =
212 dml (DELETE FROM t WHERE Client IS NULL)
213 210
214 fun subscribe id = 211 fun subscribe id =
215 cli <- self; 212 cli <- self;
216 cleanup; 213 ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[cli]});
217 ro <- oneOrNoRows (SELECT t.Channel FROM t WHERE t.Id = {[id]} AND t.Client = {[Some cli]});
218 case ro of 214 case ro of
219 None => 215 None =>
220 ch <- channel; 216 ch <- channel;
221 dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[Some cli]}, {[Some ch]})); 217 dml (INSERT INTO t (Id, Client, Channel) VALUES ({[id]}, {[cli]}, {[ch]}));
222 return ch 218 return ch
223 | Some r => 219 | Some r => return r.T.Channel
224 case r.T.Channel of
225 None => error <xml>Broadcast.subscribe: Got null result</xml>
226 | Some ch => return ch
227 220
228 fun send id msg = 221 fun send id msg =
229 cleanup;
230 queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]}) 222 queryI (SELECT t.Channel FROM t WHERE t.Id = {[id]})
231 (fn r => case r.T.Channel of 223 (fn r => Basis.send r.T.Channel msg)
232 None => error <xml>Broadcast.send: Got null result</xml>
233 | Some ch => Basis.send ch msg)
234 end 224 end