Fix for BUG#14662: view column in ORDER BY considered ambiguous if SELECT contains

the same column as an aliased and as a non-aliased column.

The problem was that Item_direct_view_ref::eq() was first comparing view columns
by name, and in this case the name of one of them is different since it is aliased.

mysql-test/r/select.result

@@ -3241,3 +3241,45 @@ f1	f2
 Warnings:
 Warning	1292	Incorrect date value: '2005-09-3a' for column 'f2' at row 1
 drop table t1;
+create table t1 (f1 int, f2 int);
+insert into t1 values (1, 30), (2, 20), (3, 10);
+create algorithm=merge view v1 as select f1, f2 from t1;
+create algorithm=merge view v2 (f2, f1) as select f1, f2 from t1;
+create algorithm=merge view v3 as select t1.f1 as f2, t1.f2 as f1 from t1;
+select t1.f1 as x1, f1 from t1 order by t1.f1;
+x1	f1
+1	1
+2	2
+3	3
+select v1.f1 as x1, f1 from v1 order by v1.f1;
+x1	f1
+1	1
+2	2
+3	3
+select v2.f1 as x1, f1 from v2 order by v2.f1;
+x1	f1
+10	10
+20	20
+30	30
+select v3.f1 as x1, f1 from v3 order by v3.f1;
+x1	f1
+10	10
+20	20
+30	30
+select f1, f2, v1.f1 as x1 from v1 order by v1.f1;
+f1	f2	x1
+1	30	1
+2	20	2
+3	10	3
+select f1, f2, v2.f1 as x1 from v2 order by v2.f1;
+f1	f2	x1
+10	3	10
+20	2	20
+30	1	30
+select f1, f2, v3.f1 as x1 from v3 order by v3.f1;
+f1	f2	x1
+10	3	10
+20	2	20
+30	1	30
+drop table t1;
+drop view v1, v2, v3;

mysql-test/t/select.test

@@ -2729,3 +2729,23 @@ select * from t1 where f2 >= '2005-09-3a';
 select * from t1 where f2 <= '2005-09-31';
 select * from t1 where f2 <= '2005-09-3a';
 drop table t1;
+
+#
+# Bug ##14662  	ORDER BY on column of a view, with an alias of the same
+# column causes ambiguous
+#
+
+create table t1 (f1 int, f2 int);
+insert into t1 values (1, 30), (2, 20), (3, 10);
+create algorithm=merge view v1 as select f1, f2 from t1;
+create algorithm=merge view v2 (f2, f1) as select f1, f2 from t1;
+create algorithm=merge view v3 as select t1.f1 as f2, t1.f2 as f1 from t1;
+select t1.f1 as x1, f1 from t1 order by t1.f1;
+select v1.f1 as x1, f1 from v1 order by v1.f1;
+select v2.f1 as x1, f1 from v2 order by v2.f1;
+select v3.f1 as x1, f1 from v3 order by v3.f1;
+select f1, f2, v1.f1 as x1 from v1 order by v1.f1;
+select f1, f2, v2.f1 as x1 from v2 order by v2.f1;
+select f1, f2, v3.f1 as x1 from v3 order by v3.f1;
+drop table t1;
+drop view v1, v2, v3;

sql/item.cc

@@ -4938,8 +4938,7 @@ bool Item_direct_view_ref::fix_fields(THD *thd, Item **reference)
 }
 
 /*
-  Compare view field's name with item's name before call to referenced
-  item's eq()
+  Compare two view column references for equality.
 
   SYNOPSIS
     Item_direct_view_ref::eq()
@@ -4947,12 +4946,13 @@ bool Item_direct_view_ref::fix_fields(THD *thd, Item **reference)
     binary_cmp  make binary comparison
 
   DESCRIPTION
-    Consider queries:
-    create view v1 as select t1.f1 as f2, t1.f2 as f1 from t1;
-    select * from v1 order by f1;
-    In order to choose right field for sorting we need to compare
-    given item's name (f1) to view field's name prior to calling
-    referenced item's eq().
+    A view column reference is considered equal to another column
+    reference if the second one is a view column and if both column
+    references point to the same field. For views 'same field' means
+    the same Item_field object in the view translation table, where
+    the view translation table contains all result columns of the
+    view. This definition ensures that view columns are resolved
+    in the same manner as table columns.
 
   RETURN
     TRUE    Referenced item is equal to given item
@@ -4962,9 +4962,18 @@ bool Item_direct_view_ref::fix_fields(THD *thd, Item **reference)
 
 bool Item_direct_view_ref::eq(const Item *item, bool binary_cmp) const
 {
-  Item *it= ((Item *) item)->real_item();
-  return (!it->name || !my_strcasecmp(system_charset_info, it->name,
-          field_name)) && ref && (*ref)->real_item()->eq(it, binary_cmp);
+  if (item->type() == REF_ITEM)
+  {
+    Item_ref *item_ref= (Item_ref*) item;
+    if (item_ref->ref_type() == VIEW_REF)
+    {
+      Item *item_ref_ref= *(item_ref->ref);
+      DBUG_ASSERT((*ref)->type() == FIELD_ITEM &&
+                  (item_ref_ref->type() == FIELD_ITEM));
+      return (*ref == item_ref_ref);
+    }
+  }
+  return FALSE;
 }
 
 void Item_null_helper::print(String *str)