How do you debug MySQL stored procedures?

Cory_House_26180 0
Viewed 209806

My current process for debugging stored procedures is very simple. I create a table called "debug" where I insert variable values from the stored procedure as it runs. This allows me to see the value of any variable at a given point in the script, but is there a better way to debug MySQL stored procedures?

stored-procedures mysql debugging database
16 Answers

I do something very similar to you.

I'll usually include a DEBUG param that defaults to false and I can set to true at run time. Then wrap the debug statements into an "If DEBUG" block.

I also use a logging table with many of my jobs so that I can review processes and timing. My Debug code gets output there as well. I include the calling param name, a brief description, row counts affected (if appropriate), a comments field and a time stamp.

Good debugging tools is one of the sad failings of all SQL platforms.

TrickyNixon_124240

I just simply place select statements in key areas of the stored procedure to check on current status of data sets, and then comment them out (--select...) or remove them before production.

Ash_Machine_356150

MySQL user defined variable (shared in session) could be used as logging output:

DELIMITER ;;
CREATE PROCEDURE Foo(tableName VARCHAR(128))
BEGIN
  SET @stmt = CONCAT('SELECT * FROM ', tableName);
  PREPARE pStmt FROM @stmt;
  EXECUTE pStmt;
  DEALLOCATE PREPARE pStmt;
  -- uncomment after debugging to cleanup
  -- SET @stmt = null;
END;;
DELIMITER ;

call Foo('foo');
select @stmt;

will output:

SELECT * FROM foo
user_19991850

Answer corresponding to this by @Brad Parks Not sure about the MySQL version, but mine was 5.6, hence a little bit tweaking works:

I created a function debug_msg which is function (not procedure) and returns text(no character limit) and then call the function as SELECT debug_msg(params) AS my_res_set, code as below:

CREATE DEFINER=`root`@`localhost` FUNCTION `debug_msg`(`enabled` INT(11), `msg` TEXT) RETURNS text CHARSET latin1
    READS SQL DATA
BEGIN
    IF enabled=1 THEN
    return concat('** DEBUG:', "** ", msg);
    END IF;
END

DELIMITER $$
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_func_call`(
 IN RegionID VARCHAR(20),
 IN RepCurrency INT(11),
 IN MGID INT(11),
 IN VNC VARCHAR(255)
)
BEGIN
    SET @enabled = TRUE;
    SET @mainQuery = "SELECT * FROM Users u";
    SELECT `debug_msg`(@enabled, @mainQuery) AS `debug_msg1`;
    SET @lastQuery = CONCAT(@mainQuery, " WHERE u.age>30);
    SELECT `debug_msg`(@enabled, @lastQuery) AS `debug_msg2`;
END $$
DELIMITER
user_13979810
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