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Re: MySQL NDB cluster lock
Posted by: Martin Sköld
Date: October 26, 2016 04:19AM

Hello,

Prior to mysql-5.7 there is unfortunately no way of finding what
connection is holding a metadata lock. In 5.7 there is a system table:
https://dev.mysql.com/doc/refman/5.7/en/metadata-locks-table.html
The ndbcluster global schema locks are not directly related since
they are used to synchronize meta data operations between several
mysql servers connected to the cluster. A drop table would typically
acquire a local metadata lock first and then a ndbcluster global schema lock
to ensure that the drop is acknowledged from all mysql servers.
The output from the processlist indicate that it didn't manage to
lock the table locally, so some other connection is accessing the
same table. If you provide some more information what other statements/queries
are being executed we might be able to help some more.

best regards,
Martin Sköld

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