[openstack-dev] [Keystone] Best way to do something MySQL-specific?

Clint Byrum clint at fewbar.com
Mon Jul 1 17:35:24 UTC 2013

The way the new keystone-manage command "token_flush" works right now
is quite broken by MySQL and InnoDB's gap locking behavior:


Presumably other SQL databases like PostgreSQL will have similar problems
with doing massive deletes, but I am less familiar with them.

I am trying to solve this in keystone, and my first attempt is here:


However, MySQL does not support using "LIMIT" in a sub-query that
is feeding an IN() clause, so that approach will not work. Likewise,
sqlalchemy does not support the MySQL specific extension to DELETE which
allows it to have a LIMIT clause.

Now, I can do some hacky things, like just deleting all of the expired
tokens from the oldest single second, but that could also potentially
be millions of tokens, and thus, millions of gaps to lock.

So, there is just not one way to work for all databases, and we have to
have a special mode for MySQL.

I was wondering if anybody has suggestions and/or examples of how to do
that with sqlalchemy.

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