BUG#20310212 PARTITION DDL- CRASH AFTER THD::NOCHECK_REGISTER_ITEM_

Problem :
---------
Issue-1: The root cause for the issues is that (col1 > 1) is not a
valid partition function and we should have thrown error at much early
stage [partition_info::check_partition_info]. We are not checking
sub-partition expression when partition expression is NULL.

Issue-2: Potential issue for future if any partition function needs to
change item tree during open/fix_fields. We should release changed
items, if any, before doing closefrm when we open the partitioned table
during creation in create_table_impl.

Solution :
----------
1.check_partition_info() - Check for sub-partition expression even if no
partition expression.
[partition by ... columns(...) subpartition by hash(<expr>)]

2.create_table_impl() - Assert that the change list is empty before doing
closefrm for partitioned table. Currently no supported partition function
seems to be changing item tree during open.
Reviewed-by: Mattias Jonsson <mattias.jonsson@oracle.com>

RB: 9345

mysql-test/r/partition_error.result

@@ -1089,7 +1089,7 @@ partition by key (a)
 subpartition by hash (sin(a+b))
 (partition x1 (subpartition x11, subpartition x12),
 partition x2 (subpartition x21, subpartition x22));
-ERROR HY000: It is only possible to mix RANGE/LIST partitioning with HASH/KEY partitioning for subpartitioning
+ERROR HY000: This partition function is not allowed
 select load_file('$MYSQLD_DATADIR/test/t1.par');
 load_file('$MYSQLD_DATADIR/test/t1.par')
 NULL

mysql-test/t/partition_error.test

@@ -1145,7 +1145,7 @@ subpartition by hash (rand(a+b));
 #
 # Subpartition by hash, wrong subpartition function
 #
---error ER_SUBPARTITION_ERROR
+--error ER_PARTITION_FUNCTION_IS_NOT_ALLOWED
 CREATE TABLE t1 (
 a int not null,
 b int not null,

sql/partition_info.cc

-/* Copyright (c) 2006, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2006, 2015, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1109,15 +1109,22 @@ bool partition_info::check_partition_info(THD *thd, handlerton **eng_type,
   {
     int err= 0;
 
+    /* Check for partition expression. */
     if (!list_of_part_fields)
     {
       DBUG_ASSERT(part_expr);
       err= part_expr->walk(&Item::check_partition_func_processor, 0,
                            NULL);
-      if (!err && is_sub_partitioned() && !list_of_subpart_fields)
-        err= subpart_expr->walk(&Item::check_partition_func_processor, 0,
-                                NULL);
     }
+
+    /* Check for sub partition expression. */
+    if (!err && is_sub_partitioned() && !list_of_subpart_fields)
+    {
+      DBUG_ASSERT(subpart_expr);
+      err= subpart_expr->walk(&Item::check_partition_func_processor, 0,
+                              NULL);
+    }
+
     if (err)
     {
       my_error(ER_PARTITION_FUNCTION_IS_NOT_ALLOWED, MYF(0));

sql/sql_table.cc

@@ -3913,6 +3913,12 @@ static bool check_if_created_table_can_be_opened(THD *thd,
   result= (open_table_def(thd, &share, 0) ||
            open_table_from_share(thd, &share, "", 0, (uint) READ_ALL,
                                  0, &table, TRUE));
+  /*
+    Assert that the change list is empty as no partition function currently
+    needs to modify item tree. May need call THD::rollback_item_tree_changes
+    later before calling closefrm if the change list is not empty.
+  */
+  DBUG_ASSERT(thd->change_list.is_empty());
   if (! result)
     (void) closefrm(&table, 0);