A fix: bug#6931: Date Type column problem when using UNION-Table

       bug#7833:  Wrong datatype of aggregate column is returned

5 files changed, 103 insertions, 16 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 7357bc06f11..9965cb792be 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -245,6 +245,7 @@ static Field::field_cast_enum field_cast_date[]=
  Field::FIELD_CAST_BLOB, Field::FIELD_CAST_STOP};
 static Field::field_cast_enum field_cast_newdate[]=
 {Field::FIELD_CAST_NEWDATE,
+ Field::FIELD_CAST_DATE,
  Field::FIELD_CAST_DATETIME,
  Field::FIELD_CAST_STRING, Field::FIELD_CAST_VARSTRING,
  Field::FIELD_CAST_BLOB, Field::FIELD_CAST_STOP};
@@ -6024,6 +6025,40 @@ Field *make_field(char *ptr, uint32 field_length,
 }
 
 
+/*
+  Check if field_type is appropriate field type
+  to create field for tmp table using
+  item->tmp_table_field() method
+
+  SYNOPSIS
+    field_types_to_be_kept()
+    field_type     - field type
+
+  NOTE
+    it is used in function get_holder_example_field()
+    from item.cc
+
+  RETURN
+    1 - can use item->tmp_table_field() method
+    0 - can not use item->tmp_table_field() method
+
+*/
+
+bool field_types_to_be_kept(enum_field_types field_type)
+{
+  switch (field_type)
+  {
+    case FIELD_TYPE_DATE:
+    case FIELD_TYPE_NEWDATE:
+    case FIELD_TYPE_TIME:
+    case FIELD_TYPE_DATETIME:
+      return 1;
+    default:
+      return 0;
+  }
+}
+
+
 /* Create a field suitable for create of table */
 
 create_field::create_field(Field *old_field,Field *orig_field)
diff --git a/sql/field.h b/sql/field.h
index 27a01a69273..fd0f2f9c2f1 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -1265,6 +1265,7 @@ int set_field_to_null(Field *field);
 int set_field_to_null_with_conversions(Field *field, bool no_conversions);
 bool test_if_int(const char *str, int length, const char *int_end,
 		 CHARSET_INFO *cs);
+bool field_types_to_be_kept(enum_field_types field_type);
 
 /*
   The following are for the interface with the .frm file
diff --git a/sql/item.cc b/sql/item.cc
index ab29c147dfb..d61d628e8fa 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -2639,7 +2639,53 @@ void Item_cache_row::bring_value()
 }
 
 
-Item_type_holder::Item_type_holder(THD *thd, Item *item)
+/*
+  Returns field for temporary table dependind on item type
+
+  SYNOPSIS
+    get_holder_example_field()
+    thd            - thread handler
+    item           - pointer to item
+    table          - empty table object
+
+  NOTE
+    It is possible to return field for Item_func 
+    items only if field type of this item is 
+    date or time or datetime type.
+    also see function field_types_to_be_kept() from
+    field.cc
+
+  RETURN
+    # - field
+    0 - no field
+*/
+
+Field *get_holder_example_field(THD *thd, Item *item, TABLE *table)
+{
+  DBUG_ASSERT(table);
+
+  Item_func *tmp_item= 0;
+  if (item->type() == Item::FIELD_ITEM)
+    return (((Item_field*) item)->field);
+  if (item->type() == Item::FUNC_ITEM)
+    tmp_item= (Item_func *) item;
+  else if (item->type() == Item::SUM_FUNC_ITEM)
+  {
+    Item_sum *item_sum= (Item_sum *) item;
+    if (item_sum->keep_field_type())
+    {
+      if (item_sum->args[0]->type() == Item::FIELD_ITEM)
+        return (((Item_field*) item_sum->args[0])->field);
+      if (item_sum->args[0]->type() == Item::FUNC_ITEM)
+        tmp_item= (Item_func *) item_sum->args[0];
+    }
+  }
+  return (tmp_item && field_types_to_be_kept(tmp_item->field_type()) ?
+          tmp_item->tmp_table_field(table) : 0);
+}
+
+
+Item_type_holder::Item_type_holder(THD *thd, Item *item, TABLE *table)
   :Item(thd, item), item_type(item->result_type()),
    orig_type(item_type)
 {
@@ -2649,10 +2695,7 @@ Item_type_holder::Item_type_holder(THD *thd, Item *item)
     It is safe assign pointer on field, because it will be used just after
     all JOIN::prepare calls and before any SELECT execution
   */
-  if (item->type() == Item::FIELD_ITEM)
-    field_example= ((Item_field*) item)->field;
-  else
-    field_example= 0;
+  field_example= get_holder_example_field(thd, item, table);
   max_length= real_length(item);
   maybe_null= item->maybe_null;
   collation.set(item->collation);
@@ -2692,25 +2735,23 @@ inline bool is_attr_compatible(Item *from, Item *to)
           (to->maybe_null || !from->maybe_null) &&
           (to->result_type() != STRING_RESULT ||
            from->result_type() != STRING_RESULT ||
-           my_charset_same(from->collation.collation,
-                           to->collation.collation)));
+          (from->collation.collation == to->collation.collation)));
 }
 
 
-bool Item_type_holder::join_types(THD *thd, Item *item)
+bool Item_type_holder::join_types(THD *thd, Item *item, TABLE *table)
 {
   uint32 new_length= real_length(item);
   bool use_new_field= 0, use_expression_type= 0;
   Item_result new_result_type= type_convertor[item_type][item->result_type()];
-  bool item_is_a_field= item->type() == Item::FIELD_ITEM;
-
+  Field *field= get_holder_example_field(thd, item, table);
+  bool item_is_a_field= field;
   /*
     Check if both items point to fields: in this case we
     can adjust column types of result table in the union smartly.
   */
   if (field_example && item_is_a_field)
   {
-    Field *field= ((Item_field *)item)->field;
     /* Can 'field_example' field store data of the column? */
     if ((use_new_field=
          (!field->field_cast_compatible(field_example->field_cast_type()) ||
@@ -2751,7 +2792,7 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
         It is safe to assign a pointer to field here, because it will be used
         before any table is closed.
       */
-      field_example= ((Item_field*) item)->field;
+      field_example= field;
     }
 
     old_cs= collation.collation->name;
diff --git a/sql/item.h b/sql/item.h
index 237a8f7efac..e0de7452eec 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1321,14 +1321,14 @@ protected:
   Item_result orig_type;
   Field *field_example;
 public:
-  Item_type_holder(THD*, Item*);
+  Item_type_holder(THD*, Item*, TABLE *);
 
   Item_result result_type () const { return item_type; }
   enum Type type() const { return TYPE_HOLDER; }
   double val();
   longlong val_int();
   String *val_str(String*);
-  bool join_types(THD *thd, Item *);
+  bool join_types(THD *thd, Item *, TABLE *);
   Field *example() { return field_example; }
   static uint32 real_length(Item *item);
   void cleanup()
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 027a21db7ac..882316d57d7 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -148,6 +148,7 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
   SELECT_LEX *sl, *first_select;
   select_result *tmp_result;
   bool is_union;
+  TABLE *empty_table= 0;
   DBUG_ENTER("st_select_lex_unit::prepare");
 
   describe= test(additional_options & SELECT_DESCRIBE);
@@ -239,13 +240,21 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       goto err;
     if (sl == first_select)
     {
+      /*
+        We need to create an empty table object. It is used
+        to create tmp_table fields in Item_type_holder.
+        The main reason of this is that we can't create
+        field object without table.
+      */
+      DBUG_ASSERT(!empty_table);
+      empty_table= (TABLE*) thd->calloc(sizeof(TABLE));
       types.empty();
       List_iterator_fast<Item> it(sl->item_list);
       Item *item_tmp;
       while ((item_tmp= it++))
       {
 	/* Error's in 'new' will be detected after loop */
-	types.push_back(new Item_type_holder(thd_arg, item_tmp));
+	types.push_back(new Item_type_holder(thd_arg, item_tmp, empty_table));
       }
 
       if (thd_arg->is_fatal_error)
@@ -264,7 +273,8 @@ int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
       Item *type, *item_tmp;
       while ((type= tp++, item_tmp= it++))
       {
-	if (((Item_type_holder*)type)->join_types(thd_arg, item_tmp))
+        if (((Item_type_holder*)type)->join_types(thd_arg, item_tmp,
+                                                  empty_table))
 	  DBUG_RETURN(-1);
       }
     }