Async proposal

[wiikviz]

-- an example typeof
let a = async
    return 2;
end async
print($a); -- async
print(typeof($a)); -- "async"
print(${await($a)}); -- 2

-- an example lambda
let test_ret = () -> begin 
	return 2;
end;

let res = async test_ret();
print(${await($res)}); -- 2

let test_async = (x) -> begin 
	return $x+2;
end;
let res1 = async test_async(1);
let res2 = async test_async(2);
print(${await([$res1, $res2])}); -- [3, 4]

-- an example of async without return and with one
let a = async
	create table T1 as select 1,2 union select 2,3; 
end async;
print($a); -- async
print(${await($a)}); -- None

let b = async
	return (select * from table T1); 
end async;
print($b); -- task
print(${await($b)}); -- [[1,2], [3,4]]

-- an example with different engines
let async1 = async
   create table spark_t1 as select 'spark' on engine 'spark'; 
   return $mixql.execution.engine;
end async;
let async2 = async
    create table hive_t1 as select 'hive' on engine 'hive'; 
    return $mixql.execution.engine;
end async;
print(await([$async1, $async2])); -- race conditions

-- an example race conditions
let x = 0;
let t1 = async
   let global x = 1;
   print($x); -- race conditions
   return $x;
end async;

let t2 = async
   let global  x = 2;
   print($x); -- race conditions
   return $x;
end async;

let t3 = async
   print($x); -- race conditions
   return $x;
end async;

print(await([$t1, $t2, $t3])); -- race conditions

-- an example timeout
let ex =await(async
				sleep(10); -- sleep 10 seconds
		      end async,
		      5); -- wait 5 seconds

print($ex.name); -- AsyncTimeoutException

-- an example exception
let t1 = async
	raise "exp1", "task 1 failed"
end async;

let t2 = async
	raise "exp2", "task 2 failed"
end async;

let res= await([$t1, $t2]);
print(res[0].name, " ", res[0].message); -- exp1 task 1 failed
print(res[1].name, " ", res[1].message); -- exp2 task 2 failed

-- an example cancel
let t1 = async
	sleep(5);
	return 1;
end async;

cancel($t1);
print(await($t1)); -- AsyncCanceledException

-- an example combine
let t1 = async
	create table t1 as select 1 as c;
end async;
let t2 = async
	create table t2 as select 2 as c;
end async;
let t3 = async
	return (select sum(c) from select * from t1 union select * from t2);
end async;

let res = combine([$t1, $t2], $t3);
print(await($t3)); -- 3

--VS

let t1 = async
	create table t1 as select 1 as c;
end async;
let t2 = async
	create table t2 as select 2 as c;
end async;
let t3 = async
	await([$t1,$t2]);
	return (select sum(c) from select * from t1 union select * from t2);
end async;

print(await($t3)); -- 3

-- an example with local context
let x = 0;
let t1 = async
   let x = 1;
   print($x); -- 1
   return $x;
end async;

let t2 = async
   let x = 2;
   print($x); -- 2
   return $x;
end async;

let t3 = async
   print($x); -- 0
   return $x;
end async;

print(await([$t1, $t2, $t3])); -- [1,2,0]
print($x); -- 0

-- an example of lazy evaluation 1
let t1 = async
    return (select * from super_big_table_1);
end async;

let t2 = async
   return (select * from super_big_table_2);
end async;

let t3 = async
   return (select * from small_table);
end async;

print(awaitFirst([$t1, $t2, $t3])); 

-- an example of lazy evaluation 2
let x = 0;
let t1 = async
   print($x); -- 5

    let x = 1;
    let t2 = async
       print($x); -- 1
    end async;

    await($t2);
end async;

let x=5;
print(await($t1)) 

-- an example of running without await
let tick_tok = async
    while true loop
	   sleep(60); -- sleep 60 seconds
	   print(getTime());
    end loop
end async;

run($tick_tok);

print($tick_tock.isActive); -- true

let sum =(select sum(c1) from super_big_table);
print($sum);