Addition to the fix to LP bug#994275.

It is problem of constant propagated to ref* access method (the problem was hiden by using debug binaries for testing).

sql/sql_select.cc

@@ -1289,8 +1289,19 @@ JOIN::optimize()
         store_key *key_copy= tab->ref.key_copy[key_copy_index];
         if (key_copy->type() == store_key::FIELD_STORE_KEY)
         {
-          store_key_field *field_copy= ((store_key_field *)key_copy);
-          field_copy->change_source_field((Item_field *) item);
+          if (item->basic_const_item())
+          {
+            /* It is constant propagated here */
+            tab->ref.key_copy[key_copy_index]=
+              new store_key_const_item(*tab->ref.key_copy[key_copy_index],
+                                       item);
+          }
+          else
+          {
+            store_key_field *field_copy= ((store_key_field *)key_copy);
+            DBUG_ASSERT(item->type() == Item::FIELD_ITEM);
+            field_copy->change_source_field((Item_field *) item);
+          }
         }
       }
       key_copy_index++;

sql/sql_select.h

@@ -1468,6 +1468,11 @@ class store_key :public Sql_alloc
       to_field=field_arg->new_key_field(thd->mem_root, field_arg->table,
                                         ptr, null, 1);
   }
+  store_key(store_key &arg)
+    :null_key(arg.null_key), to_field(arg.to_field),
+             null_ptr(arg.null_ptr), err(arg.err)
+
+  {}
   virtual ~store_key() {}			/** Not actually needed */
   virtual enum Type type() const=0;
   virtual const char *name() const=0;
@@ -1572,6 +1577,10 @@ class store_key_item :public store_key
 	       null_ptr_arg ? null_ptr_arg : item_arg->maybe_null ?
 	       &err : (uchar*) 0, length), item(item_arg), use_value(val)
   {}
+  store_key_item(store_key &arg, Item *new_item, bool val)
+    :store_key(arg), item(new_item), use_value(val)
+  {}
+
 
   enum Type type() const { return ITEM_STORE_KEY; }
   const char *name() const { return "func"; }
@@ -1617,11 +1626,14 @@ class store_key_const_item :public store_key_item
   store_key_const_item(THD *thd, Field *to_field_arg, uchar *ptr,
 		       uchar *null_ptr_arg, uint length,
 		       Item *item_arg)
-    :store_key_item(thd, to_field_arg,ptr,
+    :store_key_item(thd, to_field_arg, ptr,
 		    null_ptr_arg ? null_ptr_arg : item_arg->maybe_null ?
 		    &err : (uchar*) 0, length, item_arg, FALSE), inited(0)
   {
   }
+  store_key_const_item(store_key &arg, Item *new_item)
+    :store_key_item(arg, new_item, FALSE), inited(0)
+  {}
 
   enum Type type() const { return CONST_ITEM_STORE_KEY; }
   const char *name() const { return "const"; }