nuno-faria commented on code in PR #16716:
URL: https://github.com/apache/datafusion/pull/16716#discussion_r2196943824


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datafusion/physical-plan/src/joins/hash_join.rs:
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@@ -1498,6 +1498,23 @@ impl HashJoinStream {
 
         let timer = self.join_metrics.join_time.timer();
 
+        // if the left side is empty, we can skip the (potentially expensive) 
join operation

Review Comment:
   I think so. Can you point out where the probe repartition is being 
triggered? In the `process_probe_batch` itself I think we can also skip 
creating the hashes when the build side is empty, but I measured and it didn't 
have a relatively big impact on performance.



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