Index: sql/handler.h
===================================================================
--- sql/handler.h	(revision 25779)
+++ sql/handler.h	(revision 25780)
@@ -151,6 +151,10 @@
 #define HA_READ_RANGE           8       /* can find all records in a range */
 #define HA_ONLY_WHOLE_INDEX	16	/* Can't use part key searches */
 #define HA_KEYREAD_ONLY         64	/* Support HA_EXTRA_KEYREAD */
+// no IO if read data when scan index
+//  i.e index is covering
+// skipping 128 because SOME product has HA_KEY_SCAN_NOT_ROR
+#define HA_CLUSTERED_INDEX      256
 
 /*
   bits in alter_table_flags: