FROM A FUNCTION

Scenario:

In a stored procedure, CREATE TABLE statement is not allowed.  But an
exception is provided for CREATE TEMPORARY TABLE.  We can create a temporary
table in a stored procedure.

Let there be two stored functions f1 and f2 and two stored procedures p1 and
p2.  Their properties are as follows:

. stored function f1() calls stored procedure p1().
. stored function f2() calls stored procedure p2().
. stored procedure p1() creates temporary table t1.
. stored procedure p2() does DML on t1.

Consider the following situation:

1.  Autocommit mode is on. 
2.  select f1()
3.  select f2()

Step 2:  In this step, t1 would be created via p1().  A table level transaction
lock would have been taken.  The ::external_lock() would not have been called
on this table.  At the end of step 2, because of autocommit mode on, this table
level lock will be released.

Step 3:  When we execute DML on table t1 via p2() we have two problems:

Problem 1:

The function ha_innobase::external_lock() would have been called but since
it is a select query no table level locks would have been taken.  Hence the
following assert will fail:

ut_ad(lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));

Solution:

The solution would be to identify this situation and take a table level lock
and use the proper lock type prebuilt->select_lock_type = LOCK_X for DML
operations.

Problem 2:

Another problem is that in step 3, ha_innobase::open() is never called on
the table t1.  

Solution:

The solution would be to identify this situation and call re-init the handler
of table t1.

rb#6429 approved by Krunal.