Problem: Segmentation fault in add_group_and_distinct_keys() when accessing
field of what is assumed to be an Item_field object.
Cause: In case of views, the item added to list by is_indexed_agg_distinct()
was not of type Item_field, but Item_ref.
Resolution: Add the real Item_field object, the one referred to by
Item_ref object, to the list, instead.
At the end of execution top level join execution
we cleanup this join with true argument.
It leads to underlying join cleanup(subquery) with true argument too
and to tmp_table_param->field array cleanup which is required later.
The problem is that Item_func_set_user_var does not set
result_filed which leads to unnecessary repeated excution of subquery
on final stage.
The fix is to set result_field for Item_func_set_user_var.
server"
Bug appears only on Windows platform. Freeing memory in
TMP_TABLE_PARAM::cleanup() allocated by new Copy_fields[0] in
setup_copy_fields() results in memory destruction. In test IF used instead
of CONCAT because IF have more stable crash.
Call pthread_mutex_destroy() on not used mutex.
Changed comments in .h and .c files from // -> /* */
Added detection of mutex on which one didn't call pthread_mutex_destroy()
Fixed bug in create_tmp_field() which causes a memory overrun in queries that uses "ORDER BY constant_expression"
Added optimisation for ORDER BY NULL
