Bug#30882 Dropping a temporary table inside a stored function may cause a server crash

If a stored function that contains a drop temporary table statement
is invoked by a create temporary table of the same name may cause
a server crash. The problem is that when dropping a table no check
is done to ensure that table is not being used by some outer query
(or outer statement), potentially leaving the outer query with a
reference to a stale (freed) table.

The solution is when dropping a temporary table, always check if
the table is being used by some outer statement as a temporary
table can be dropped inside stored procedures.

The check is performed by looking at the TABLE::query_id value for
temporary tables. To simplify this check and to solve a bug related
to handling of temporary tables in prelocked mode, this patch changes
the way in which this member is used to track the fact that table is
used/unused. Now we ensure that TABLE::query_id is zero for unused
temporary tables (which means that all temporary tables which were
used by a statement should be marked as free for reuse after it's
execution has been completed).


mysql-test/include/handler.inc:
  Add test case for side effect of Bug#30882
mysql-test/r/handler_innodb.result:
  Add test case result for side effect of Bug#30882
mysql-test/r/handler_myisam.result:
  Add test case result for side effect of Bug#30882
mysql-test/r/sp-error.result:
  Add test case result for Bug#30882
mysql-test/t/sp-error.test:
  Add test case for Bug#30882
sql/event_db_repository.cc:
  Update close_thread_tables call, no more default values.
sql/mysql_priv.h:
  Remove implicit default parameters values of the close_thread_tables
  function as no callers are using it.
sql/slave.cc:
  Update close_thread_tables call, no more default values
sql/sp_head.cc:
  Update close_thread_tables call, no more default values
sql/sql_base.cc:
  Changed the approach to distinguishing currently unused temporary tables.
  Now we ensure that such tables always have TABLE::query_id set to 0 and
  use this fact to perform checks during opening and dropping of temporary
  tables. This means that we have to call close_thread_tables() even for
  statements which use only temporary tables. To make this call cheaper,
  we re-factored close_thread_tables() to not take LOCK_open unless there
  are open base tables.
sql/sql_handler.cc:
  Properly close temporary tables associated with a handler.
sql/sql_insert.cc:
  close_temporary_table is now merged into drop_temporary_table.
sql/sql_parse.cc:
  Now the condition doesn't cover all cases because close_thread_tables()
  must be called even for statements that use only temporary tables.
sql/sql_table.cc:
  Use drop_temporary_table which perform checks to verify if
  the table is not being used. Error path problem is due to
  a handler tables issue and is going to be addressed in bug
  31397.
sql/table.h:
  Rename previously unused clear_query_id and document the usage of
  query_id and open_by_handler.

mysql-test/include/handler.inc

@@ -566,3 +566,35 @@ reap;
 connection default;
 drop table t2;
 disconnect flush;
+
+#
+# Bug#30882 Dropping a temporary table inside a stored function may cause a server crash
+#
+# Test HANDLER statements in conjunction with temporary tables. While the temporary table
+# is open by a HANDLER, no other statement can access it.
+#
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+create temporary table t1 (a int, b char(1), key a(a), key b(a,b));
+insert into t1 values (0,"a"),(1,"b"),(2,"c"),(3,"d"),(4,"e"),
+                      (5,"f"),(6,"g"),(7,"h"),(8,"i"),(9,"j");
+select a,b from t1;
+handler t1 open as a1;
+handler a1 read a first;
+handler a1 read a next;
+handler a1 read a next;
+--error ER_CANT_REOPEN_TABLE
+select a,b from t1;
+handler a1 read a prev;
+handler a1 read a prev;
+handler a1 read a=(6) where b="g";
+handler a1 close;
+select a,b from t1;
+handler t1 open as a2;
+handler a2 read a first;
+handler a2 read a last;
+handler a2 read a prev;
+handler a2 close;
+drop table t1;