Github user KurtYoung commented on the issue:
https://github.com/apache/flink/pull/4445
I would bet on deserialization for it. And why sorter suffers more
regression than hash join is that sorter will cause more deserializations
during compare records than hash join.
Despite the regression we will face, i think it's still worthy since we can
avoid an extra copy from network to runtime. It's better if we can take the
extra copy into account during benchmark, but it's ok we don't have it.
+1 to merge this.
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