TRX_ROLLBACK_LAST_SQL_STAT_FOR_MYSQL

Bug 20008555 - ASSERTION FAILURE IN TRX0TRX.CC LINE 1689 |
               ABORT SIG 6 IN TRX_MARK_SQL_STAT_END

Issue here is, when transaction is in XA_PREPARE state, innodb
transaction is registered for a "SELECT" query execution with
the prepare state. Assert condition to check whether this
transaction is in active state or not during commit and
rollback operations are resulting in the issues reported in
the bugs.

In the open_tables function, we have check to verify transaction
is in prepare or idle state. But this check is executed only
when table_list is not empty. And this check is before getting
the tables used by stored routines. So for the SELECT with
only stored function call (e.g. SELECT f1()) this check is skipped
as table_list is empty and while processing we add table
used by routine to table_list. In "handle_query" function,
lock_tables is called for the tables used in query. This
in turn calls the ha_innobase::external_lock which registers
a transaction with a prepare state.

In the scenario mentioned in bug#19941492, while executing
the stored function, the transaction state is checked in
open_tables and error is returned. In this case, transaction
is rolled back. Since transaction state is prepare instead
of active, assert condition mentioned in the rollback code failed.

In the scenario mentioned in bug#20008555, since system
variable "sql_select_limit" is set to 0. Stored function
is not executed, error related transaction state is not
reported. So transaction is committed. Since transaction state
is prepare instead of active, assert condition mentioned in the
commit code failed.

Fix:
------------
In open_tables function, check to avoid operations when
transaction is in idle or prepare state and when any
tables are used is very early. The check is before even
processing tables used in stored routines. This is the route
cause for both scenarios mentioned in the big report of
19941492 and 20008555. To fix this issue, moved check after
preparing all the tables used in the query.