Manual merge of #11335 bugfix

3 files changed, 46 insertions, 2 deletions

diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index b669a8c426d..bbcea4705fa 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -321,6 +321,22 @@ Field *Item_sum_hybrid::create_tmp_field(bool group, TABLE *table,
       field->flags&= ~NOT_NULL_FLAG;
     return field;
   }
+  /*
+    DATE/TIME fields have STRING_RESULT result types.
+    In order to preserve field type, it's needed to handle DATE/TIME
+    fields creations separately.
+  */
+  switch (args[0]->field_type()) {
+  case MYSQL_TYPE_DATE:
+    return new Field_date(maybe_null, name, table, collation.collation);
+  case MYSQL_TYPE_TIME:
+    return new Field_time(maybe_null, name, table, collation.collation);
+  case MYSQL_TYPE_TIMESTAMP:
+  case MYSQL_TYPE_DATETIME:
+    return new Field_datetime(maybe_null, name, table, collation.collation);
+  default:
+    break;
+  }
   return Item_sum::create_tmp_field(group, table, convert_blob_length);
 }
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index c09a35c1fc0..33476979c7e 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -7944,7 +7944,15 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
 				   item->name, table, item->unsigned_flag);
     break;
   case STRING_RESULT:
-    if (item->max_length > 255 && convert_blob_length)
+    enum enum_field_types type;
+    /*
+      DATE/TIME fields have STRING_RESULT result type. To preserve
+      type they needed to be handled separately.
+    */
+    if ((type= item->field_type()) == MYSQL_TYPE_DATETIME ||
+        type == MYSQL_TYPE_TIME || type == MYSQL_TYPE_DATE)
+      new_field= item->tmp_table_field_from_field_type(table);
+    else if (item->max_length > 255 && convert_blob_length)
       new_field= new Field_varstring(convert_blob_length, maybe_null,
                                      item->name, table,
                                      item->collation.collation);
@@ -8055,6 +8063,20 @@ Field *create_tmp_field(THD *thd, TABLE *table,Item *item, Item::Type type,
   case Item::DEFAULT_VALUE_ITEM:
   {
     Item_field *field= (Item_field*) item;
+    /*
+      If item have to be able to store NULLs but underlaid field can't do it,
+      create_tmp_field_from_field() can't be used for tmp field creation.
+    */
+    if (field->maybe_null && !field->field->maybe_null())
+    {
+      Field *res= create_tmp_field_from_item(thd, item, table, NULL,
+                                       modify_item, convert_blob_length);
+      *from_field= field->field;
+      if (res && modify_item)
+        ((Item_field*)item)->result_field= res;
+      return res;
+    }
+
     if (table_cant_handle_bit_fields && 
         field->field->type() == FIELD_TYPE_BIT)
       return create_tmp_field_from_item(thd, item, table, copy_func,
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index f2b637dc5f4..c414f5e9e72 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -235,7 +235,13 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
 
     if ((res= (res || thd_arg->is_fatal_error)))
       goto err;
-    if (sl == first_select)
+    /*
+      Use items list of underlaid select for derived tables to preserve
+      information about fields lengths and exact types
+    */
+    if (!is_union)
+      types= first_select_in_union()->item_list;
+    else if (sl == first_select)
     {
       /*
         We need to create an empty table object. It is used