Bug #55973 Assertion `thd->transaction.stmt.is_empty()'

           on CREATE TABLE .. SELECT I_S.PART

This assert was triggered if an InnoDB table was created using
CREATE TABLE ... AS SELECT where the query used an I_S table, and
a view existed in the database. It would also be triggered for
any statement changing an InnoDB table (e.g. INSERT, UPDATE, DELETE)
which had a subquery referencing an I_S table.

The assert was triggered if open_normal_and_derived_tables() failed
and a statement transaction had been started. This will usually not
happen as tables are opened before a statement transaction is started.
However, e.g. CREATE TABLE ... AS SELECT starts a transaction in order
to insert tuples into the new table. And if the subquery references
an I_S table, all current tables and views can be opened in order to
fill the I_S table on the fly. If a view is discovered, open will fail
as it is instructed to open tables only (OPEN_TABLE_ONLY). This would
cause the assert to be triggered.

The assert was added in the patch for Bug#52044 and was therefore
not in any released versions of the server.

This patch fixes the problem by adjusting the assert to take into
consideration the possibility of tables being opened as part of
an I_S query. This is similar to what is already done for 
close_tables_for_reopen().

Test case added to information_schema_inno.test.

mysql-test/r/information_schema_inno.result

@@ -89,3 +89,15 @@ UNIQUE_CONSTRAINT_NAME
 NULL
 drop table t2;
 set foreign_key_checks = 1;
+#
+# Bug#55973 Assertion `thd->transaction.stmt.is_empty()'
+#           on CREATE TABLE .. SELECT I_S.PART
+#
+DROP TABLE IF EXISTS t1;
+DROP VIEW IF EXISTS v1;
+CREATE VIEW v1 AS SELECT 1;
+CREATE TABLE t1 engine = InnoDB AS
+SELECT * FROM information_schema.partitions
+WHERE table_schema= 'test' AND table_name= 'v1';
+DROP TABLE t1;
+DROP VIEW v1;

mysql-test/t/information_schema_inno.test

@@ -89,3 +89,23 @@ from information_schema.referential_constraints
 where constraint_schema = schema();
 drop table t2;
 set foreign_key_checks = 1;
+
+
+--echo #
+--echo # Bug#55973 Assertion `thd->transaction.stmt.is_empty()'
+--echo #           on CREATE TABLE .. SELECT I_S.PART
+--echo #
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+DROP VIEW IF EXISTS v1;
+--enable_warnings
+
+CREATE VIEW v1 AS SELECT 1;
+# This used to case an assert.
+CREATE TABLE t1 engine = InnoDB AS
+  SELECT * FROM information_schema.partitions
+  WHERE table_schema= 'test' AND table_name= 'v1';
+
+DROP TABLE t1;
+DROP VIEW v1;

sql/sql_base.cc

@@ -5411,8 +5411,14 @@ bool open_normal_and_derived_tables(THD *thd, TABLE_LIST *tables, uint flags)
 
   DBUG_RETURN(0);
 end:
-  /* No need to rollback statement transaction, it's not started. */
-  DBUG_ASSERT(thd->transaction.stmt.is_empty());
+  /*
+    No need to commit/rollback the statement transaction: it's
+    either not started or we're filling in an INFORMATION_SCHEMA
+    table on the fly, and thus mustn't manipulate with the
+    transaction of the enclosing statement.
+  */
+  DBUG_ASSERT(thd->transaction.stmt.is_empty() ||
+              (thd->state_flags & Open_tables_state::BACKUPS_AVAIL));
   close_thread_tables(thd);
   /* Don't keep locks for a failed statement. */
   thd->mdl_context.rollback_to_savepoint(mdl_savepoint);