MySQL Cluster transaction isolation level - READ_COMMITTED

Posted by Doori Bar on Server Fault See other posts from Server Fault or by Doori Bar
Published on 2010-10-05T18:42:17Z Indexed on 2014/08/24 22:23 UTC
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transactions

I'm learning by mostly reading the documentation. Unfortunately, http://dev.mysql.com/doc/refman/5.1/en/set-transaction.html#isolevel_read-committed

doesn't say anything, while it says everything. Confused? Me too.

ndb engine supports only "READ_COMMITTED" transaction isolation level.

A. It starts by saying "sets and reads its own fresh snapshot", which I translate to: The transaction is having a separated 'zone' which whatever it stores there - is what it reads back.

B. While out-side of the transaction, the old-values are unlocked.

C. It continues with: "for locking reads" sentence - No idea what it means.

Question: they claim only READ_COMMITTED transaction isolation level is supported, but while handling a BLOB or a TEXT, they say the isolation is now "locked for reading" too. So is it a contradiction? can a transaction LOCK for reading just as well while handling something other than BLOB/TEXT? (such as integers)

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