Current table is placed into read_tables set of the current join_tab->select
so get_mm_parts function thinks that current table's record is read and
tries to calculate WHERE condition with the fields of the record.
Result of these calculations is unpredictable.
Looks funny - outcome of the SELECT depends on the queries executed before.
Anyway i think we should have testcase on this part of the code.
Removed usage of @r/result as this made life hard when testing different
table handlers.
Allow concurrent inserts if no update/binary log.
Don't remove key_cache at flush tables.
Fixed bug in SELECT DISTINCT SUM()...
