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From:Mark Matthews Date:February 10 2006 6:54pm
Subject:Re: InnoDB and locking
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Patrick Duda wrote:
> 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?
> 
> Thanks
> 
> Patrick
> 
> 

Patrick,

Are you sure the table is using the InnoDB storage engine? What does the
output of "SHOW CREATE TABLE " for the table in question say?

	-Mark
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Thread
InnoDB and lockingPatrick Duda10 Feb
  • Re: InnoDB and lockingAlec.Cawley10 Feb
    • Re: InnoDB and lockingPatrick Duda10 Feb
  • Re: InnoDB and lockingMark Matthews10 Feb
    • Re: InnoDB and lockingPatrick Duda10 Feb
  • Re: InnoDB and lockingPeter Brawley11 Feb
Re: InnoDB and lockingHeikki Tuuri11 Feb