Almost for fun, I did this little experiment: take the output of an EXPLAIN from sql, and execute it in MAL (mclient -l mal).

I found only *1* detail which doesn't parse, here it is in a minimal example:

* Got the explain of a trivial query:

sql>\f raw

sql>explain select name from sys.functions;

% .explain # table_name

% mal # name

% clob # type

% 94 # length

function user.s4_1():void;

X_32:void := querylog.define("explain select name from sys.functions;","default_pipe",21);

X_16 := bat.new(nil:oid,nil:str);

X_24 := bat.append(X_16,"sys.functions");

X_19 := bat.new(nil:oid,nil:str);

X_26 := bat.append(X_19,"name");

X_20 := bat.new(nil:oid,nil:str);

X_27 := bat.append(X_20,"varchar");

X_21 := bat.new(nil:oid,nil:int);

X_29 := bat.append(X_21,256);

X_23 := bat.new(nil:oid,nil:int);

X_31 := bat.append(X_23,0);

X_1 := sql.mvc();

C_2:bat[:oid] := sql.tid(X_1,"sys","functions");

X_5:bat[:str] := sql.bind(X_1,"sys","functions","name",0);

(C_8,r1_8) := sql.bind(X_1,"sys","functions","name",2);

X_11:bat[:str] := sql.bind(X_1,"sys","functions","name",1);

X_13 := sql.delta(X_5,C_8,r1_8,X_11);

X_14 := algebra.projection(C_2,X_13);

sql.resultSet(X_24,X_26,X_27,X_29,X_31,X_14);

end user.s4_1;

# optimizer.mitosis()

# optimizer.dataflow()

* Opened a MAL session, initialized sql, and pasted the function above:

mal>sql.init();

mal>function user.s4_1():void;

mal> X_32:void := querylog.define("explain select name from sys.functions;","default_pipe",21);

mal> X_16 := bat.new(nil:oid,nil:str);

mal> X_24 := bat.append(X_16,"sys.functions");

mal> X_19 := bat.new(nil:oid,nil:str);

mal> X_26 := bat.append(X_19,"name");

mal> X_20 := bat.new(nil:oid,nil:str);

mal> X_27 := bat.append(X_20,"varchar");

mal> X_21 := bat.new(nil:oid,nil:int);

mal> X_29 := bat.append(X_21,256);

mal> X_23 := bat.new(nil:oid,nil:int);

mal> X_31 := bat.append(X_23,0);

mal> X_1 := sql.mvc();

mal> C_2:bat[:oid] := sql.tid(X_1,"sys","functions");

mal> X_5:bat[:str] := sql.bind(X_1,"sys","functions","name",0);

mal> (C_8,r1_8) := sql.bind(X_1,"sys","functions","name",2);

mal> X_11:bat[:str] := sql.bind(X_1,"sys","functions","name",1);

mal> X_13 := sql.delta(X_5,C_8,r1_8,X_11);

mal> X_14 := algebra.projection(C_2,X_13);

mal> sql.resultSet(X_24,X_26,X_27,X_29,X_31,X_14);

mal>end user.s4_1;

MAPI = (monetdb) /tmp/.s.monetdb.54500

QUERY = end user.s4_1;

ERROR = !TypeException:user.s4_1[17]:'sql.delta' undefined in: X_13:any := sql.delta(X_5:bat[:str],C_8:bat[:oid],r1_8:bat[:any],X_11:bat[:str]);

mal>

The error is easy to find: sql.delta() expects r1_8 to be of type :bat[:str], but it gets :bat[:any] instead.

* If I fix it manually:

mal>function user.s4_1():void;

mal> X_32:void := querylog.define("explain select name from sys.functions;","default_pipe",21);

mal> X_16 := bat.new(nil:oid,nil:str);

mal> X_24 := bat.append(X_16,"sys.functions");

mal> X_19 := bat.new(nil:oid,nil:str);

mal> X_26 := bat.append(X_19,"name");

mal> X_20 := bat.new(nil:oid,nil:str);

mal> X_27 := bat.append(X_20,"varchar");

mal> X_21 := bat.new(nil:oid,nil:int);

mal> X_29 := bat.append(X_21,256);

mal> X_23 := bat.new(nil:oid,nil:int);

mal> X_31 := bat.append(X_23,0);

mal> X_1 := sql.mvc();

mal> C_2:bat[:oid] := sql.tid(X_1,"sys","functions");

mal> X_5:bat[:str] := sql.bind(X_1,"sys","functions","name",0);

mal> (C_8,r1_8:bat[:str]) := sql.bind(X_1,"sys","functions","name",2);

mal> X_11:bat[:str] := sql.bind(X_1,"sys","functions","name",1);

mal> X_13 := sql.delta(X_5,C_8,r1_8,X_11);

mal> X_14 := algebra.projection(C_2,X_13);

mal> sql.resultSet(X_24,X_26,X_27,X_29,X_31,X_14);

mal>end user.s4_1;

mal>

Yay, it works.

* The reason I write this email:

- I suspect that the output of EXPLAIN is not meant to necessarily be re-parsable, but just to be informative

- Nevertheless, it really is almost re-parsable. I tried a much larger query, (2000+ lines of MAL), and this was the only detail. It looks like fixing that small detail could be worth it.

- Also, I wonder if this is, in fact, a bug. Binds to access types 0 and 1 do get the right type information. Why not access type 2?