Dynamically converting all DATETIME values in a database to UTC in MySQL - mysql

Question

Currently, our application's database stores all DATETIME values in GMT-8, which is generally very bad. We're trying to convert the application and all data to use UTC.
I am trying to write a one-off stored procedure that will query my database's schema, find all columns of type DATETIME or TIMESTAMP, and automatically UPDATE the columns by converting values with the CONVERT_TZ() function.
Using all of the information I've found so far about cursors, dynamic statement preparation, and error handling, I've come up with this:
DELIMITER $$
CREATE PROCEDURE `sp_convertDBtoUTC`()
BEGIN
DECLARE `_rollback` BOOL DEFAULT 0;
DECLARE done INT DEFAULT 0;
DECLARE tname VARCHAR(64);
DECLARE cname VARCHAR(64);
DECLARE dt_columns CURSOR FOR
SELECT table_name, column_name
FROM information_schema.columns
WHERE table_schema = 'my_schema'
AND data_type IN ('datetime', 'timestamp')
ORDER BY table_name, column_name;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
DECLARE CONTINUE HANDLER FOR SQLEXCEPTION SET `_rollback` = 1;
START TRANSACTION;
OPEN dt_columns;
table_loop:
LOOP
FETCH dt_columns INTO tname, cname;
IF done = 1 THEN
LEAVE table_loop;
END IF;
SET #stmt = CONCAT('UPDATE ',tname,' SET ',cname, ' = CONVERT_TZ(',cname, ', \'America/Los_Angeles\', \'UTC\')');
PREPARE stmt FROM #stmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END LOOP;
CLOSE dt_columns;
IF `_rollback` THEN
ROLLBACK;
ELSE
COMMIT;
END IF;
END$$
This seems to run without errors, but does nothing. If I add a SELECT #stmt statement in there, I get multiple result sets with the correct SQL, e.g. UPDATE tz_test SET dts = CONVERT_TZ(dts, 'America/Los_Angeles', 'UTC'). If I run this statement manually, the table gets updated as expected.
However, when running the stored procedure to update the entire database, the data in the tables doesn't actually get updated, and I don't understand why.
I'm using the following as a test:
CREATE TABLE tz_test (id INT auto_increment, dts DATETIME, PRIMARY KEY (id));
INSERT INTO tz_test (dts) VALUES (NOW());
SELECT * FROM tz_test;
CALL sp_convertDBtoUTC();
SELECT * FROM tz_test;
I would have expected the second result set to contain the modified datetime value, but the two result sets are identical. Why is this?

Answer 1

When trying to run these queries through MySQL Workbench, they were actually failing silently because of Safe Mode (no mass update/delete without a reference to a primary key).
Once I turned it off and reconnected, the entire process worked flawlessly.