mbutrovich commented on code in PR #3858:
URL: https://github.com/apache/datafusion-comet/pull/3858#discussion_r3029613996
##########
native/shuffle/src/partitioners/multi_partition.rs:
##########
@@ -203,6 +203,36 @@ impl MultiPartitionShuffleRepartitioner {
return Ok(());
}
+ // For zero-column schemas (e.g. COUNT queries), assign all rows to
partition 0.
+ // No hashing or expression evaluation needed — just route through
normal buffering.
+ if input.num_columns() == 0 {
+ let num_rows = input.num_rows();
+ self.metrics.baseline.record_output(num_rows);
+ // All rows go to partition 0: partition_starts = [0, num_rows,
num_rows, ...]
+ // partition_row_indices = [0, 1, 2, ..., num_rows-1]
+ let mut scratch = std::mem::take(&mut self.scratch);
Review Comment:
This still looks way more complicated than what I would expect. Why do we
need scratch space and to write `num_rows` `partition_row_indices`. Why are we
"partitioning" rows that don't exist?
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