Re: statistics state

[Marko Mäkelä]

Pavel,

The InnoDB trx->op_info is "waiting in InnoDB queue" for each transaction you are listing. The string "statistics" is printed by innobase_mysql_print_thd() from thd->proc_info.

A quick grep of the MySQL source tree (which I am not very familiar with) reveals that the threads are probably stuck inside make_join_statistics(), called from JOIN::optimize(). I presume that the query optimizer needs to build some statistics in order to select a good execution plan.

When MySQL requests statistics (estimated numbers of distinct values for each key) from InnoDB, InnoDB will do some random dives to the index B-trees to give estimates. These estimates can be off or oscillate. It's in our long-term TODO to have persistent statistics.

Your problem looks like a MySQL issue, because trx->op_info would be set to something else if InnoDB were executing dict_update_statistics() [the random dives].

Please consider reporting a bug in the "Server" category. But try to prepare a test case, or otherwise the bug will probably end up flagged "Can't repeat".

With best regards,

Marko Mäkelä
Innobase Oy/Oracle Corp.