table tab : {Id : int, Val : int} PRIMARY KEY Id
fun cache id =
res <- oneOrNoRows (SELECT tab.Val
FROM tab
WHERE tab.Id = {[id]});
return
Reading {[id]}.
{case res of
None => ?
| Some row => {[row.Tab.Val]}}
(* fun cache2 id v = *)
(* res <- oneOrNoRows (SELECT tab.Val *)
(* FROM tab *)
(* WHERE tab.Id = {[id]} AND tab.Val = {[v]}); *)
(* return *)
(* Reading {[id]}. *)
(* {case res of *)
(* None => Nope, that's not it. *)
(* | Some _ => Hooray! You guessed it!} *)
(* *)
fun cache2 id1 id2 =
res1 <- oneOrNoRows (SELECT tab.Val
FROM tab
WHERE tab.Id = {[id1]});
res2 <- oneOrNoRows (SELECT tab.Val
FROM tab
WHERE tab.Id = {[id2]});
return
Reading {[id1]} and {[id2]}.
{case (res1, res2) of
(Some _, Some _) => Both are there.
| _ => One of them is missing.}
fun flush id =
dml (UPDATE tab
SET Val = Val * (Id + 2) / Val - 3
WHERE Id = {[id]} OR Id = {[id - 1]} OR Id = {[id + 1]});
return
Changed {[id]}!
val flush17 =
dml (UPDATE tab
SET Val = Val * (Id + 2) / Val - 3
WHERE Id = 17);
return
Changed specifically 17!
(* fun flush id = *)
(* res <- oneOrNoRows (SELECT tab.Val *)
(* FROM tab *)
(* WHERE tab.Id = {[id]}); *)
(* (case res of *)
(* None => dml (INSERT INTO tab (Id, Val) *)
(* VALUES ({[id]}, 0)) *)
(* | Some row => dml (UPDATE tab *)
(* SET Val = {[row.Tab.Val + 1]} *)
(* WHERE Id = {[id]} OR Id = {[id + 1]})); *)
(* return *)
(* {case res of *)
(* None => Initialized {[id]}! *)
(* | Some row => Incremented {[id]}!} *)
(* *)