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From Christian Mittendorf <christian.mittend...@freenet.de>
Subject Duplicate Key Problem
Date Wed, 12 Jul 2006 08:28:37 GMT
Hello!

We are running a MySQL 5.0 server using InnoDB tables for our  
applications. We have multiple web applications accessing this same  
database and the system is running smooth and without problems (almost).

But yesterday we were experiencing some strange errors. During the  
afternoon some CayenneRuntimeExceptions appeared in the log file,  
which were caused by:

Caused by: java.sql.SQLException: null,  message from server:  
"Duplicate entry '4353880' for key 1"

A bit later other CayenneRuntimeException appeared. For those  
exceptions the cause was:

Caused by: java.sql.SQLException: Deadlock found when trying to get  
lock; Try restarting transaction,  message from server: "Lock wait  
timeout exceeded; try restarting transaction"

I'm now wondering, are both errors related to each other?

There are, from my point of view, two possible causes for the  
"Duplicate entry..." message:

- two Insert statements on the same object, which might be possible  
if the application is clustered, which our applications are not, or
- dual use of the same key in different objects

Has anybody else experienced something like that? Are there any hints  
what I might do to avoid such situations?

Christian





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