olap.test, olap.result:

  Added test case for bug #4767.
item_sum.cc:
  Added a correct setting of the maybe_null flag for a copy of 
  an Item_sum object where the argument was a field of an inner table
  in an outer join read from a temporary table.
  It's part of the fix for bug #4767.
sql_select.cc:
  Made change_refs_to_tmp_fields work correctly
  for test case of bug #4767 where Item_sum::get_tmp_table_item
  failed to build a correct copy of an Item_sum object referring
  to a field in a temporary table.
  It looks like a hack yet.

mysql-test/r/olap.result

@@ -271,3 +271,39 @@ i	i	COUNT(*)
 100	NULL	2
 NULL	NULL	2
 drop table t1,t2;
+CREATE TABLE user_day(
+user_id INT NOT NULL,
+date DATE NOT NULL,
+UNIQUE INDEX user_date (user_id, date)
+);
+INSERT INTO user_day VALUES
+(1, '2004-06-06' ),
+(1, '2004-06-07' ),
+(2, '2004-06-06' );
+SELECT
+d.date AS day,
+COUNT(d.user_id) as sample,
+COUNT(next_day.user_id) AS not_cancelled
+FROM user_day d
+LEFT JOIN user_day next_day 
+ON next_day.user_id=d.user_id AND 
+next_day.date= DATE_ADD( d.date, interval 1 day )
+GROUP BY day;
+day	sample	not_cancelled
+2004-06-06	2	1
+2004-06-07	1	0
+SELECT
+d.date AS day,
+COUNT(d.user_id) as sample,
+COUNT(next_day.user_id) AS not_cancelled
+FROM user_day d
+LEFT JOIN user_day next_day 
+ON next_day.user_id=d.user_id AND 
+next_day.date= DATE_ADD( d.date, interval 1 day )
+GROUP BY day
+WITH ROLLUP;
+day	sample	not_cancelled
+2004-06-06	2	1
+2004-06-07	1	0
+NULL	3	1
+DROP TABLE user_day;

mysql-test/t/olap.test

@@ -88,3 +88,40 @@ INSERT INTO t2 VALUES (100),(200);
 SELECT i, COUNT(*) FROM t1 GROUP BY i WITH ROLLUP;
 SELECT t1.i, t2.i, COUNT(*) FROM t1,t2 GROUP BY t1.i,t2.i WITH ROLLUP;
 drop table t1,t2;
+
+#bug #4767: ROLLUP with LEFT JOIN 
+
+CREATE TABLE user_day(
+  user_id INT NOT NULL,
+  date DATE NOT NULL,
+  UNIQUE INDEX user_date (user_id, date)
+);
+
+INSERT INTO user_day VALUES
+  (1, '2004-06-06' ),
+  (1, '2004-06-07' ),
+  (2, '2004-06-06' );
+
+SELECT
+       d.date AS day,
+       COUNT(d.user_id) as sample,
+       COUNT(next_day.user_id) AS not_cancelled
+  FROM user_day d
+       LEFT JOIN user_day next_day 
+       ON next_day.user_id=d.user_id AND 
+          next_day.date= DATE_ADD( d.date, interval 1 day )
+  GROUP BY day;
+
+SELECT
+       d.date AS day,
+       COUNT(d.user_id) as sample,
+       COUNT(next_day.user_id) AS not_cancelled
+  FROM user_day d
+       LEFT JOIN user_day next_day 
+       ON next_day.user_id=d.user_id AND 
+          next_day.date= DATE_ADD( d.date, interval 1 day )
+  GROUP BY day
+    WITH ROLLUP;
+
+DROP TABLE user_day;
+

sql/item_sum.cc

@@ -159,7 +159,10 @@ Item *Item_sum::get_tmp_table_item(THD *thd)
       if (!arg->const_item())
       {
 	if (arg->type() == Item::FIELD_ITEM)
+        {
+           arg->maybe_null= result_field_tmp->maybe_null();
 	  ((Item_field*) arg)->field= result_field_tmp++;
+        }
 	else
 	  sum_item->args[i]= new Item_field(result_field_tmp++);
       }

sql/sql_select.cc

@@ -4995,6 +4995,8 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields,
 	    blob_count++;
 	  }
 	  ((Item_sum*) item)->args[i]= new Item_field(new_field);
+          if (((Item_sum*) item)->arg_count == 1)
+            ((Item_sum*) item)->result_field= new_field;
 	}
       }
     }