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How to Lock a Table - MySql

Posted on 2007-10-08
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Last Modified: 2008-01-09
I have a table called 'matrix' in mysql.  I am subtracting 10 from a field called 'dollarsGained'.  To accomplish this, I will use the following code:

 LOCK TABLES matrix WRITE;
 UPDATE matrix SET dollarsGained = dollarsGained - 10;
 UNLOCK TABLES;

I am having trouble with the locking portion of this code and would like the answers to the following questions:

1) After executing the statement ' LOCK TABLES matrix WRITE;' how do I check that the table is actually locked?
2) How do I just unlock the table 'matix' without unlocking all of the tables in the database?
3) How do I check that the table is actually unlocked?

Server info:
MySQL 5.0.45-community-nt via TCP/IP
MySQL Client Version 5.1.11
MYISAM tables
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Question by:jmokrauer
3 Comments
 
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Accepted Solution

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Julian Matz earned 1500 total points
ID: 20038422
I haven't personally worked with this before, but see if the following might help...
http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_get-lock
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Expert Comment

by:savuandrei
ID: 20482078
You don't need all that locking because the query is atomic. There is no race condition problem here. Any query you send to MySQL is atomic.

If your change will need to affect other fields my advice is to use transactions and InnoDB. All you have to do is enable the InnoDB engine in the MySQL configuration file and change table type.
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Author Comment

by:jmokrauer
ID: 20484748
makes sense, thanks!
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