I would investigate ways of writing that long running job so that it does not require locking a table for long periods of time. Use relative updates, break the procedure down into smaller lockable steps with pauses for other programs etc.
Clyde wrote:
Hi,
As per a previous thread I have found that when you use "lock Tables" MySql will wait indefinitely for the lock - No timeout or error message.
Therefore let me explain my question.
Scenario:
User 1 locks files for a long running job. (write lock that prevents any access to the files)
User 2 logs on, then try's to lock or use these files but can't because user 1 already has the lock. (even a simple "select * from xxx" will wait forever)
The program for user 2 will just appear to hang. How do I give feed back to user 2 to say something like: "Unable to lock/use files after waiting 30 seconds, try again later" or whatever. IE I would like the program to be able to return control after a specific amount of time if the lock is not satisfied in order to give feedback to the user, rather than the the program just wait and appearing to hang.
Better still if there is a system variable or something I can check first to see if the file is locked - but I can't seem to find this in the docs.
Most other databases I have used have a timeout value (like the record lock for innodb) so I am having trouble dealing with this scenario.
Any Ideas.
Thanks
Clyde England
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