A bug fix and test case for a bug that appears in quereis where there

is a GROUP BY a column that is not NOT NULL and ORDER BY is done by
another column.

Even better fix would be to make a separate function for this.

mysql-test/r/group_by.result

@@ -393,3 +393,26 @@ One	Two	sum(Four)
 1	2	16
 1	3	16
 drop table if exists t1;
+drop table if exists t1,t2;
+create table t1 (id integer primary key not null auto_increment, gender char(1));
+insert into t1 values(NULL, 'M');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'M');
+create table t2 (user_id integer not null, timestamp datetime);
+insert into t2 values (1, sysdate());
+insert into t2 values (2, sysdate());
+insert into t2 values (1, sysdate());
+insert into t2 values (3, sysdate());
+insert into t2 values (4, sysdate());
+insert into t2 values (4, sysdate());
+select u.gender as gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender;
+gender	dist_count	percentage
+F	3	60.00
+M	1	20.00
+select u.gender as  gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender  order by percentage;
+gender	dist_count	percentage
+M	1	20.00
+F	3	60.00
+drop table t1,t2;

mysql-test/t/group_by.test

@@ -299,3 +299,20 @@ insert into t1 values (1,3,3,4);
 insert into t1 values (1,3,4,4);
 select One, Two, sum(Four) from t1 group by One,Two;
 drop table if exists t1;
+drop table if exists t1,t2;
+create table t1 (id integer primary key not null auto_increment, gender char(1));
+insert into t1 values(NULL, 'M');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'F');
+insert into t1 values(NULL, 'M');
+create table t2 (user_id integer not null, timestamp datetime);
+insert into t2 values (1, sysdate());
+insert into t2 values (2, sysdate());
+insert into t2 values (1, sysdate());
+insert into t2 values (3, sysdate());
+insert into t2 values (4, sysdate());
+insert into t2 values (4, sysdate());
+select u.gender as gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender;
+select u.gender as  gender, count(distinct  u.id) as dist_count, (count(distinct u.id)/5*100) as percentage from t1 u, t2 l where l.user_id = u.id group by u.gender  order by percentage;
+drop table t1,t2;

sql/sql_select.cc

@@ -135,7 +135,7 @@ static TABLE *get_sort_by_table(ORDER *a,ORDER *b,TABLE_LIST *tables);
 static void calc_group_buffer(JOIN *join,ORDER *group);
 static bool alloc_group_fields(JOIN *join,ORDER *group);
 static bool make_sum_func_list(JOIN *join,List<Item> &fields);
-static bool change_to_use_tmp_fields(List<Item> &func);
+static bool change_to_use_tmp_fields(List<Item> &func, bool change=false);
 static bool change_refs_to_tmp_fields(THD *thd, List<Item> &func);
 static void init_tmptable_sum_functions(Item_sum **func);
 static void update_tmptable_sum_func(Item_sum **func,TABLE *tmp_table);
@@ -788,7 +788,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
       tmp_table=tmp_table2;
       join.join_tab[0].table=0;			// Table is freed
 
-      if (change_to_use_tmp_fields(all_fields)) // No sum funcs anymore
+      if (change_to_use_tmp_fields(all_fields,true)) // No sum funcs anymore
 	goto err;
       join.tmp_table_param.field_count+=join.tmp_table_param.sum_func_count;
       join.tmp_table_param.sum_func_count=0;
@@ -6764,7 +6764,7 @@ make_sum_func_list(JOIN *join,List<Item> &fields)
 */
 
 static bool
-change_to_use_tmp_fields(List<Item> &items)
+change_to_use_tmp_fields(List<Item> &items, bool change)
 {
   List_iterator<Item> it(items);
   Item *item_field,*item;
@@ -6776,6 +6776,11 @@ change_to_use_tmp_fields(List<Item> &items)
       continue;
     if (item->type() == Item::FIELD_ITEM)
     {
+      if (change)
+      {
+	((Item_field*) item)->result_field->null_ptr=0;
+	item->maybe_null=0;
+      }
       ((Item_field*) item)->field=
 	((Item_field*) item)->result_field;
     }