dblink_write implement [FEAT MERGE]

Co-authored-by: zzg19950727 <1071026277@qq.com>
Co-authored-by: xianyu-w <707512433@qq.com>

src/sql/optimizer/ob_help_log_plan.h

@@ -26,7 +26,8 @@ public:
      : ObLogPlan(ctx, help_stmt)
      {}
   virtual ~ObHelpLogPlan() {}
-  int generate_raw_plan();
+protected:
+  int generate_normal_raw_plan();
 private:
   DISALLOW_COPY_AND_ASSIGN(ObHelpLogPlan);
 };