diff --git a/src/storage/column_store/ob_co_merge_dag.cpp b/src/storage/column_store/ob_co_merge_dag.cpp
index e63153ad6..87726ffac 100644
--- a/src/storage/column_store/ob_co_merge_dag.cpp
+++ b/src/storage/column_store/ob_co_merge_dag.cpp
@@ -413,6 +413,7 @@ ObCOMergeBatchExeDag::ObCOMergeBatchExeDag()
    start_cg_idx_(0),
    end_cg_idx_(0),
    retry_create_task_(false),
+   progress_inited_(false),
    merge_progress_(nullptr)
 {
 }
@@ -618,10 +619,12 @@ int ObCOMergeBatchExeDag::init_merge_progress()
   if (OB_UNLIKELY(nullptr == dag_net || nullptr == (ctx = dag_net->get_merge_ctx()))) {
     ret = OB_ERR_UNEXPECTED;
     LOG_WARN("dag_net or ctx is null", K(ret), KPC(dag_net));
-  } else if (OB_ISNULL(merge_progress_)
+  } else if (!progress_inited_
+      && OB_ISNULL(merge_progress_)
       && OB_FAIL(ctx->prepare_merge_progress(merge_progress_, this, start_cg_idx_, end_cg_idx_))) {
     STORAGE_LOG(WARN, "fail to prepare merge_progress", K(ret));
   }
+  progress_inited_ = true; // execute only once regardless of any failure
   return ret;
 }
 
@@ -751,18 +754,18 @@ int ObCOMergeBatchExeTask::process()
 void ObCOMergeBatchExeTask::merge_start()
 {
   int tmp_ret = OB_SUCCESS;
+  ObIDag::ObDagGuard guard(*dag_);
   ObCOMergeBatchExeDag *execute_dag = static_cast<ObCOMergeBatchExeDag*>(dag_);
-  ctx_->cg_merge_info_array_[execute_dag->get_start_cg_idx()]->get_sstable_merge_info().update_start_time();
+  // execute init_progress only once
   if (OB_TMP_FAIL(execute_dag->init_merge_progress())) {
     LOG_WARN_RET(tmp_ret, "failed to init merge progress");
   }
+  // each task has one merger, and all mergers share the progress
   ObCOMerger *co_merger = static_cast<ObCOMerger*>(merger_);
   co_merger->set_merge_progress(execute_dag->get_merge_progress());
-  {
-    ObIDag::ObDagGuard guard(*dag_);
-    if (!execute_dag->get_time_guard().is_empty()) {
-      execute_dag->get_time_guard().reuse();
-    }
+  // execute time click init only once
+  if (execute_dag->get_time_guard().is_empty()) {
+    ctx_->cg_merge_info_array_[execute_dag->get_start_cg_idx()]->get_sstable_merge_info().update_start_time();
     execute_dag->dag_time_guard_click(ObStorageCompactionTimeGuard::DAG_WAIT_TO_SCHEDULE);
   }
 }
diff --git a/src/storage/column_store/ob_co_merge_dag.h b/src/storage/column_store/ob_co_merge_dag.h
index 873473247..3f0a04768 100644
--- a/src/storage/column_store/ob_co_merge_dag.h
+++ b/src/storage/column_store/ob_co_merge_dag.h
@@ -164,6 +164,7 @@ private:
   uint32_t start_cg_idx_;
   uint32_t end_cg_idx_;
   bool retry_create_task_;
+  bool progress_inited_; // inited = true & merge_progress_ = nullptr means init failed
   compaction::ObPartitionMergeProgress *merge_progress_;
 };