Bug #27084 partitioning by list seems failing when using case

creation of the partitioned table could fail as we created Item-s for
it's list function in thd->mem_root, and then do Item->fix_fields
in the context of other table->mem_root (so that memory alloced
there was alloced in this table->mem_root). As we freed the
table->mem_root before we do thd->free_items, our Item-s had
pointers to the freed memory, that caused the crash

mysql-test/r/partition.result

@@ -1219,4 +1219,14 @@ SELECT t2.id FROM t2 WHERE t2.id IN (SELECT id FROM t1 WHERE status = 'Verified'
 id
 22589
 drop table t1, t2;
+CREATE TABLE `t1` ( `a` varchar(1)) ENGINE=MyISAM
+PARTITION BY LIST (CASE a WHEN 'a' THEN 1
+WHEN 'b' THEN 2
+WHEN 'c' THEN 3
+END)  (
+PARTITION a VALUES IN (1), 
+PARTITION b VALUES IN (2),
+PARTITION c VALUES IN (3)
+);
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/partition.test

@@ -1463,4 +1463,19 @@ SELECT t2.id FROM t2 WHERE t2.id IN (SELECT id FROM t1 WHERE status = 'Verified'
 
 drop table t1, t2;
 
+#
+# Bug #27084 partitioning by list seems failing when using case 
+#
+CREATE TABLE `t1` ( `a` varchar(1)) ENGINE=MyISAM
+ PARTITION BY LIST (CASE a WHEN 'a' THEN 1
+ WHEN 'b' THEN 2
+ WHEN 'c' THEN 3
+ END)  (
+ PARTITION a VALUES IN (1), 
+ PARTITION b VALUES IN (2),
+ PARTITION c VALUES IN (3)
+);
+
+DROP TABLE t1;
+
 --echo End of 5.1 tests

sql/item_cmpfunc.cc

@@ -2099,6 +2099,21 @@ void Item_func_case::print(String *str)
   str->append(STRING_WITH_LEN("end)"));
 }
 
+
+void Item_func_case::cleanup()
+{
+  uint i;
+  DBUG_ENTER("Item_func_case::cleanup");
+  Item_func::cleanup();
+  for (i= 0; i <= (uint)DECIMAL_RESULT; i++)
+  {
+    delete cmp_items[i];
+    cmp_items[i]= 0;
+  }
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Coalesce - return first not NULL argument.
 */

sql/item_cmpfunc.h

@@ -1106,18 +1106,7 @@ public:
   Item *find_item(String *str);
   CHARSET_INFO *compare_collation() { return cmp_collation.collation; }
   bool check_partition_func_processor(byte *bool_arg) { return FALSE;}
-  void cleanup()
-  {
-    uint i;
-    DBUG_ENTER("Item_func_case::cleanup");
-    Item_func::cleanup();
-    for (i= 0; i <= (uint)DECIMAL_RESULT; i++)
-    {
-      delete cmp_items[i];
-      cmp_items[i]= 0;
-    }
-    DBUG_VOID_RETURN;
-  }
+  void cleanup();
 };
 
 /*

sql/sql_partition.cc

@@ -3684,6 +3684,8 @@ void get_partition_set(const TABLE *table, byte *buf, const uint index,
      table                         Table object of partitioned table
      create_table_ind              Is it called from CREATE TABLE
      default_db_type               What is the default engine of the table
+     work_part_info_used           Flag is raised if we don't create new
+                                   part_info, but used thd->work_part_info
 
    RETURN VALUE
      TRUE                          Error
@@ -3704,7 +3706,8 @@ bool mysql_unpack_partition(THD *thd, const uchar *part_buf,
                             uint part_info_len,
                             uchar *part_state, uint part_state_len,
                             TABLE* table, bool is_create_table_ind,
-                            handlerton *default_db_type)
+                            handlerton *default_db_type,
+                            bool *work_part_info_used)
 {
   bool result= TRUE;
   partition_info *part_info;
@@ -3716,6 +3719,7 @@ bool mysql_unpack_partition(THD *thd, const uchar *part_buf,
   thd->lex= &lex;
   thd->variables.character_set_client= system_charset_info;
   lex_start(thd, part_buf, part_info_len);
+  *work_part_info_used= false;
   /*
     We need to use the current SELECT_LEX since I need to keep the
     Name_resolution_context object which is referenced from the
@@ -3805,6 +3809,7 @@ bool mysql_unpack_partition(THD *thd, const uchar *part_buf,
       thd->free_items();
       part_info= thd->work_part_info;
       table->s->version= 0UL;
+      *work_part_info_used= true;
     }
   }
   table->part_info= part_info;

sql/sql_partition.h

@@ -81,7 +81,8 @@ bool mysql_unpack_partition(THD *thd, const uchar *part_buf,
                             uint part_info_len,
                             uchar *part_state, uint part_state_len,
                             TABLE *table, bool is_create_table_ind,
-                            handlerton *default_db_type);
+                            handlerton *default_db_type,
+                            bool *work_part_info_used);
 void make_used_partitions_str(partition_info *part_info, String *parts_str);
 uint32 get_list_array_idx_for_endpoint(partition_info *part_info,
                                        bool left_endpoint,

sql/table.cc

@@ -1525,21 +1525,30 @@ int open_table_from_share(THD *thd, TABLE_SHARE *share, const char *alias,
     thd->set_n_backup_active_arena(&part_func_arena, &backup_arena);
     thd->stmt_arena= &part_func_arena;
     bool tmp;
+    bool work_part_info_used;
 
     tmp= mysql_unpack_partition(thd, share->partition_info,
                                 share->partition_info_len,
                                 (uchar*)share->part_state,
                                 share->part_state_len,
                                 outparam, is_create_table,
-                                share->default_part_db_type);
+                                share->default_part_db_type,
+                                &work_part_info_used);
     outparam->part_info->is_auto_partitioned= share->auto_partitioned;
     DBUG_PRINT("info", ("autopartitioned: %u", share->auto_partitioned));
-    if (!tmp)
+    /* we should perform the fix_partition_func in either local or
+       caller's arena depending on work_part_info_used value
+    */
+    if (!tmp && !work_part_info_used)
       tmp= fix_partition_func(thd, outparam, is_create_table);
     thd->stmt_arena= backup_stmt_arena_ptr;
     thd->restore_active_arena(&part_func_arena, &backup_arena);
     if (!tmp)
+    {
+      if (work_part_info_used)
+        tmp= fix_partition_func(thd, outparam, is_create_table);
       outparam->part_info->item_free_list= part_func_arena.free_list;
+    }
     if (tmp)
     {
       if (is_create_table)