[FEAT MERGE][CP]optimizer stats enhancement

Co-authored-by: 2149 <260391947@qq.com>

src/sql/engine/ob_exec_context.cpp

@@ -130,7 +130,8 @@ ObExecContext::ObExecContext(ObIAllocator &allocator)
     table_direct_insert_ctx_(),
     errcode_(OB_SUCCESS),
     dblink_snapshot_map_(),
-    cur_row_num_(-1)
+    cur_row_num_(-1),
+    is_online_stats_gathering_(false)
 {
 }