Patrick Duda <[EMAIL PROTECTED]> wrote on 10/02/2006 16:28:56:
> I guess I don't understand this locking stuff. I have a InnoDB table
that
> has one thing in it, a counter. All I want to do is have multiple
> instances of the code read this counter and increment it. I want to
make
> sure that each one is unique.
>
> Here is what I am doing in java:
>
> c.setAutoCommit(false);
> ...
> rs = statement.executeQuery("select request_id from requestid_innodb for
> update");
> ...
> String updateQuery = "update requestid_innodb set request_id=";
> updateQuery = updateQuery + nextRequestId;
> tempStatement = c.createStatement();
> tempStatement.executeUpdate(updateQuery);
> ...
> c.commit();
> c.setAutoCommit(true);
>
> If I have multiple instances of this code running I end up with
duplicate
> keys. I thought this was suppose to lock the table so that would not
happen.
>
> What am I not doing right? What am I not understanding about locking?
I think this problem is explained in detail at
http://dev.mysql.com/doc/refman/5.0/en/innodb-locking-reads.html
Alec
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