> ------------------------------------------------------------
> revno: 2818.1.19
> revision-id: kostja@sun.com-20091103165854-7di545xruez8w207
> parent: li-bing.song@sun.com-20091103090041-zj7nedx6ok5jgges
> committer: Konstantin Osipov <kostja@sun.com>
> branch nick: 5.0-41756
> timestamp: Tue 2009-11-03 19:58:54 +0300
> message:
>   A fix and a test case for
>   Bug#41756 "Strange error messages about locks from InnoDB".
>   
>   In JT_EQ_REF (join_read_key()) access method,
>   don't try to unlock rows in the handler, unless certain that
>   a) they were locked
>   b) they are not used.
>   
>   Unlocking of rows is done by the logic of the nested join loop,
>   and is unaware of the possible caching that the access method may
>   have. This could lead to double unlocking, when a row
>   was unlocked first after reading into the cache, and then
>   when taken from cache, as well as to unlocking of rows which
>   were actually used (but taken from cache).
>   
>   Delegate part of the unlocking logic to the access method,
>   and in JT_EQ_REF count how many times a record was actually
>   used in the join. Unlock it only if it's usage count is 0.
>   
>   Implemented review comments.