[GitHub] [arrow-datafusion] houqp commented on a change in pull request #238: Fix Left join implementation is incorrect for 0 or multiple batches on the right side

[GitBox <gi...@apache.org>]

houqp commented on a change in pull request #238:
URL: https://github.com/apache/arrow-datafusion/pull/238#discussion_r624740133



##########
File path: datafusion/src/physical_plan/hash_join.rs
##########
@@ -1025,14 +1053,42 @@ impl Stream for HashJoinStream {
                     );
                     self.num_input_batches += 1;
                     self.num_input_rows += batch.num_rows();
-                    if let Ok(ref batch) = result {
+                    if let Ok((ref batch, ref left_side)) = result {
                         self.join_time += start.elapsed().as_millis() as usize;
                         self.num_output_batches += 1;
                         self.num_output_rows += batch.num_rows();
+
+                        if self.join_type == JoinType::Left {

Review comment:
       nit, I think it would be better to do an explicit match on the join type enum here to exhaust all cases. that way, when we add outer join in the future, the compiler will remind us to update the check here.




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