Patrick,
it should work. You have only shown a fragment of the application code.
Maybe there is a bug somewhere else. If you write a very simple test program
to test this, do you still get the duplicate values?
Best regards,
Heikki
Oracle Corp./Innobase Oy
InnoDB - transactions, row level locking, and foreign keys for MySQL
InnoDB Hot Backup - a hot backup tool for InnoDB which also backs up MyISAM
tables
http://www.innodb.com/order.php
----- Original Message -----
From: "Patrick Duda" <pduda@stripped>
Newsgroups: mailing.database.myodbc
Sent: Friday, February 10, 2006 9:01 PM
Subject: Re: InnoDB and locking
> At 12:54 PM 2/10/2006, Mark Matthews wrote:
>>-----BEGIN PGP SIGNED MESSAGE-----
>>Hash: SHA1
>>
>>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
>
>
> ysql> show create table requestid_innodb;
>
> +------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------+
> | Table | Create
> Table
> |
>
> +------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------+
> | requestid_innodb | CREATE TABLE `requestid_innodb` (
> `request_id` int(11) NOT NULL default '0',
> PRIMARY KEY (`request_id`)
> ) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
>
> +------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------+
> 1 row in set (0.00 sec)
>
>
>
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