[index merge] occupy das iter type

src/sql/das/iter/ob_das_iter_define.h

@@ -32,6 +32,7 @@ enum ObDASIterType : uint32_t
   DAS_ITER_SORT,
   DAS_ITER_TEXT_RETRIEVAL_MERGE,
   DAS_ITER_VEC_VID_MERGE,
+  DAS_ITER_INDEX_MERGE,
   // append DASIterType before me
   DAS_ITER_MAX
 };
@@ -59,6 +60,7 @@ enum ObDASIterTreeType : uint32_t
   ITER_TREE_GIS_LOOKUP,
   ITER_TREE_DOMAIN_LOOKUP,
   ITER_TREE_TEXT_RETRIEVAL,
+  ITER_TREE_INDEX_MERGE,
   // append iter tree type before me
   ITER_TREE_MAX
 };

src/sql/das/ob_das_define.h

@@ -85,6 +85,7 @@ enum ObDASOpType
   DAS_OP_SORT,
   DAS_OP_VEC_SCAN,
   DAS_OP_VID_MERGE,
+  DAS_OP_INDEX_MERGE,
   //append OpType before me
   DAS_OP_MAX
 };