DEBUG Statement

The SQL statements are translated into MAL programs, which are optimized and stored away in a user module. The generated code can be inspected with the MAL debugger. Its functionality is modelled after the GNU Debugger.

Example

sql>DEBUG SELECT count(*) FROM sys.tables;
mdb>#X_0=0@0:void := querylog.define("debug select count(*) from sys.tables;", "default_pipe", 27:int);
mdb>list
function user.main():void;              	#[0]
    X_0:void := querylog.define("debug select count(*) from sys.tables;", "default_pipe", 27:int);	#[1] QLOGdefineNaive
barrier X_1:bit := language.dataflow(); 	#[2] MALstartDataflow
    X_2:int := sql.mvc();               	#[3] SQLmvc
    C_3:bat[:oid] := sql.tid(X_2, "sys", "_tables");	#[4] SQLtid
    X_4:bat[:sht] := sql.bind(X_2, "sys", "_tables", "type", 0:int);	#[5] mvc_bind_wrap
    (X_5:bat[:oid], X_6:bat[:sht]) := sql.bind(X_2, "sys", "_tables", "type", 2:int);	#[6] mvc_bind_wrap
    C_7:bat[:oid] := algebra.thetaselect(X_4, C_3, 2:sht, "!=");	#[7] ALGthetaselect2
    C_8:bat[:oid] := algebra.thetaselect(X_6, nil:bat[:oid], 2:sht, "!=");	#[8] ALGthetaselect2
    C_9:bat[:oid] := sql.subdelta(C_7, C_3, X_5, C_8);	#[9] DELTAsub
    X_10:lng := aggr.count(C_9);        	#[10] ALGcount_bat
    C_11:bat[:oid] := sql.tid(X_2, "tmp", "_tables");	#[11] SQLtid
    X_12:lng := aggr.count(C_11);       	#[12] ALGcount_bat
    X_13:bat[:lng] := bat.single(X_10); 	#[13] CMDBATsingle
    X_14:bat[:lng] := bat.new(nil:lng); 	#[14] CMDBATnew
    X_15:bat[:lng] := bat.append(X_14, X_13, true);	#[15] BKCappend_force_wrap
    X_16:bat[:lng] := bat.append(X_15, X_12, true);	#[16] BKCappend_val_force_wrap
    X_17:lng := aggr.sum(X_16);         	#[17] CMDBATsum
    X_18:void := language.pass(C_3);    	#[18] MALpass
exit X_1:bit;                           	#[19]
    X_19:int := sql.resultSet(".%10", "%10", "bigint", 64:int, 0:int, 7:int, X_17);	#[20] mvc_scalar_value_wrap
end user.main;                          	#[21]
...
mdb>next
mdb>#barrier X_1=false:bit := language.dataflow();
mdb>next
mdb>#X_2=0:int := sql.mvc();
mdb>next
mdb>#C_3=nil:bat[:oid] := sql.tid(X_2=0, "sys", "_tables");
...
mdb>help
next             -- Advance to next statement
continue         -- Continue program being debugged
catch            -- Catch the next exception
break [<var>]    -- set breakpoint on current instruction or <var>
delete [<var>]   -- remove break/trace point <var>
debug <int>      -- set kernel debugging mask
step             -- advance to next MAL instruction
module           -- display a module signatures
atom             -- show atom list
finish           -- finish current call
exit             -- terminate executionr
quit             -- turn off debugging
list <obj>       -- list current program block
list #  [+#],-#  -- list current program block slice
List <obj> [#]   -- list with type information[slice]
list [#] <obj>   -- list program block after optimizer <#>
List #  [+#],-#  -- list current program block slice
var  <obj>       -- print symbol table for module
optimizer <obj>  -- display optimizer steps
print <var>      -- display value of a variable
print <var> <cnt>[<first>] -- display BAT chunk
info <var>       -- display bat variable properties
run              -- restart current procedure
where            -- print stack trace
down             -- go down the stack
up               -- go up the stack
trace <var>      -- trace assignment to variables
trap <mod>.<fcn> -- catch MAL function call in debugger
help             -- this message
mdb>#C_3=nil:bat[:oid] := sql.tid(X_2=0, "sys", "_tables");