Question

Actually I use the following sentence read on another question in this page:

SELECT UPDATE_TIME
FROM   information_schema.tables
WHERE  TABLE_SCHEMA = 'dbname'
   AND TABLE_NAME = 'tabname'

But I think that it is using a lot of process time, it will be more easy if mysql-server sends me a signal when the table is updated so I can wait until my program detects that signal.

Is this possible? I’m programming in C.

Thank you very much.

Answer 1

You can use a trigger combined with a UDF progammed in C(++) to do the notification.
Here’s dummy code.

DELIMITER $$

CREATE TRIGGER ai_table1_each AFTER INSERT ON table1 FOR EACH ROW
BEGIN
  CALL ChangeNotification('table1', 'insert', NEW.id);
END $$

DELIMITER ;

You’ll have to do a trigger for insert/delete and update. 3x per table.
You cannot add a trigger to the system tables IIRC, because these are really views and not actual tables.

You’ll need to write a UDF in C(++) called changenotification that does the notification for you.

Links:
http://dev.mysql.com/doc/refman/5.0/en/adding-udf.html
http://www.mysqludf.org/
http://dev.mysql.com/doc/refman/5.0/en/triggers.html
http://dev.mysql.com/doc/refman/5.0/en/getting-unique-id.html