Github user viirya commented on the issue:
https://github.com/apache/spark/pull/14452
@hvanhovell Got it. Thanks for the cue.
I think the thought is the same, to reuse the results of the plans wit same
results.
The performance gain of this PR is from the reuse of the spark plan of the
subqueries in CTE. It is not only for exchange plan.
For example, the TPC-DS query 64 has two CTEs with long join chain of many
tables. If we materialize the CTE subqueries in the query each time it is
referred, the performance is bad. With this de-duplication, we can just run the
long join once and reuse its results.
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