[GitHub] [arrow] icexelloss commented on a diff in pull request #34311: GH-32884: [C++] Add ordered aggregation

[via GitHub]

icexelloss commented on code in PR #34311:
URL: https://github.com/apache/arrow/pull/34311#discussion_r1123712492


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cpp/src/arrow/compute/exec/aggregate_node.cc:
##########
@@ -584,29 +775,50 @@ class GroupByNode : public ExecNode, public TracedNode {
     ARROW_ASSIGN_OR_RAISE(out_data_, Finalize());
 
     int64_t num_output_batches = bit_util::CeilDiv(out_data_.length, 
output_batch_size());
-    RETURN_NOT_OK(output_->InputFinished(this, 
static_cast<int>(num_output_batches)));
-    return plan_->query_context()->StartTaskGroup(output_task_group_id_,
-                                                  num_output_batches);
+    total_output_batches_ += static_cast<int>(num_output_batches);
+    if (is_last) {
+      ARROW_RETURN_NOT_OK(output_->InputFinished(this, total_output_batches_));
+      
RETURN_NOT_OK(plan_->query_context()->StartTaskGroup(output_task_group_id_,
+                                                           
num_output_batches));
+    } else {
+      for (int64_t i = 0; i < num_output_batches; i++) {
+        ARROW_RETURN_NOT_OK(OutputNthBatch(i));
+      }
+      ARROW_RETURN_NOT_OK(ResetAggregates());
+    }
+    return Status::OK();
   }
 
   Status InputReceived(ExecNode* input, ExecBatch batch) override {
     auto scope = TraceInputReceived(batch);
 
     DCHECK_EQ(input, inputs_[0]);
 
-    ARROW_RETURN_NOT_OK(Consume(ExecSpan(batch)));
+    auto handler = [this](const ExecBatch& full_batch, const GroupingSegment& 
segment) {
+      if (!segment.extends && segment.offset == 0) 
RETURN_NOT_OK(OutputResult());
+      auto exec_batch = full_batch.Slice(segment.offset, segment.length);
+      auto batch = ExecSpan(exec_batch);
+      RETURN_NOT_OK(Consume(batch));
+      RETURN_NOT_OK(
+          GetScalarFields(&segmenter_values_, exec_batch, 
segment_key_field_ids_));

Review Comment:
   The method name is misnomer. Looks like this method "updates the value of 
segmenter_values_ to the values of next segment", if that is correct, this 
method should probably be called sth like 
   ```
   UpdateSegmentValues(exec_batch)
   ```
   Also I don't think this method need to take `segmenter_values_` and 
`segment_key_field_ids_` because those are member variables that you can 
already access from the "this". (Similar to the "Consume" method)



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