haohuaijin commented on code in PR #19653:
URL: https://github.com/apache/datafusion/pull/19653#discussion_r2678442853
##########
datafusion/physical-plan/src/aggregates/topk_stream.rs:
##########
@@ -192,9 +211,15 @@ impl Stream for GroupedTopKAggregateStream {
}
let batch = {
let _timer = emitting_time.timer();
- let cols = self.priority_map.emit()?;
+ let mut cols = self.priority_map.emit()?;
+ // For DISTINCT case (no aggregate expressions), only
use the group key column
+ // since the schema only has one field and key/value
are the same
+ if self.aggregate_arguments.is_empty() {
+ cols.truncate(1);
+ }
Review Comment:
we can further improve this part, because for the query
```sql
select distinct id from t order by id limit 10
```
it do not have any aggregate, so we only need mantain the topk heap, and
skip the group keys
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