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From "Dag H. Wanvik" <Dag.Wan...@Sun.COM>
Subject (A)symmetry of Update and Shared locks in Derby
Date Wed, 02 Nov 2005 17:16:42 GMT

Hi,

I did some tests of Derby with Update and shared locks, to check the
compatibility. To avoid deadlocks, these locks should be implemented
asymmetrically, as shown in
http://db.apache.org/derby/docs/10.1/devguide/rdevconcepts2462.html

As I read this matrix, once a transaction has an update lock
(intention to update), a shared lock should not be granted to another
transaction. My test, whoever, indicated that a shared lock was indeed
granted (connection2 in the repro) after an update lock was taken by
the first transaction. Is this a bug or am I missing something here?

Repro:

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