1.4 Debugging CQL queries

You can debug CQL using the meta-predicates ?/1, ??/2 and ???/3:

???{[], se_lt_x :: [a-A, b-_], A == 'ELSTON_M'}.

?/1

Display a summary form of the generated SQL before and after the goal is called.

[main]  CALL   SELECT slx_2.b, slx_2.a  FROM se_lt_x AS slx_2 WHERE slx_2.a = 'ELSTON_M'
[main]  EXIT   SELECT slx_2.b, slx_2.a  FROM se_lt_x AS slx_2 WHERE slx_2.a = 'ELSTON_M' (0.006963s, 0.01cpu, 3,899 inferences)

??/1

Display the exact query (and results) in a format which can be executed directly by the DBMS (In this case, SQL Server) The generated SQL may be significantly more complicated than expected, and this can be used to debug the CQL compiler itself

[main]  CALL
DECLARE @P0 VARCHAR(50);
SET @P0 = 'ELSTON_M';
SELECT slx_450.b,
       slx_450.a
FROM se_lt_x AS slx_450
WHERE slx_450.a = @P0 AND slx_450.a COLLATE Latin1_General_CS_AS = @P0
Result: se_lt_x.b = {null}
        se_lt_x.a = 'ELSTON_M'
 (0.003304s, 0.00cpu, 359 inferences)

???/1

Display simplified SQL before the goal is called and display the results afterwards

[main]  CALL
SELECT slx_450.b,
       slx_450.a
FROM se_lt_x AS slx_450
WHERE slx_450.a = 'ELSTON_M'
Result: se_lt_x.b = {null}
        se_lt_x.a = 'ELSTON_M'
 (0.003304s, 0.00cpu, 359 inferences)