Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/10577#discussion_r49159238
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/CatalystQl.scala ---
@@ -393,8 +393,8 @@
https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation%2C+Cube%2C
overwrite)
}
- // If there are multiple INSERTS just UNION them together into on
query.
- val query = queries.reduceLeft(Union)
+ // If there are multiple INSERTS just UNION them together into one
query.
+ val query = if (queries.length == 1) queries.head else Union(queries)
--- End diff --
After the merge, I am planning to introduce a new rule in `Optimizer` to
detect if any child of `Union` can be pruned or if there exists only one child
(e.g., after pruning), we can remove the `Union` operator from the logical
plan. Not sure if this sounds good to you. Thank you!
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