Log exception info in MySQL stored procedure - mysql

Question

As I know, I can define exception handler in MySQL stored procedure, but seems I can't catch the exception message in the handler and write a log in a table for debugging purpose. I just want to know is there method to log exception code and message in MySQL store procedure?

Answer 1

You can catch the message, the error code, the sql state, ..., with the GET DIAGNOSTICS statement, in 5.6.4
See
http://dev.mysql.com/doc/refman/5.6/en/get-diagnostics.html

Answer 2

I don't remember what tutorial I copied this from. However, it has helped immensely in the versions of MySQL prior to 5.6. Thanks to whomever I learned this from!
Step 1 : Create a debug_log table. This will hold everything your write to it.
CREATE TABLE `debug_log` (
`debug_log_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`msg` varchar(512) NOT NULL,
`created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`debug_log_id`)
) ENGINE=MyISAM
Step 2 : Create a stored procedure for adding info to the debug_log table.
DELIMITER $$
USE `your_db_name_here`$$
DROP PROCEDURE IF EXISTS `log_debug`$$
CREATE DEFINER=`ss7admin`#`%` PROCEDURE `log_debug`(IN lastMsg VARCHAR(512))
BEGIN
INSERT INTO debug_log (msg) VALUES (lastMsg);
END$$
DELIMITER ;
Step 3 : Add a handler in your real stored procedure.
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
CALL log_debug(
CONCAT
(
now(),
' : Something went horribly wrong!',
'.'
)
);
CALL log_debug('Exiting now');
SET outReturnCode = 1;
END;

Answer 3

You cannot catch the message, but you can catch the error code.
Here is an example of how to deal with "Duplicate entry" (PK, UK constraint):
CREATE PROCEDURE sp_do_insert(
IN in_param1 int,
IN in_param2 int,
OUT out_status tinyint
)
BEGIN
DECLARE CONTINUE HANDLER FOR 1062 SET out_status = 1;
SET out_status = 0;
INSERT INTO tbl(field1, fiel2)
VALUES (in_param1, in_param2);
END;
If tbl has a UK constraint on field1 and you try to insert an existing value once again you will not get an error. Nothing will be inserted and status will be equal to 1.
You can also add other handlers for other error codes. And you will always know what is the error from out_status value and you will know "error message" from error_code (in handler).
You can try to play with show warnings (it shows errors/warnings for the last query) in case if out_status <> 0.
Hope it helps.