dongjoon-hyun commented on a change in pull request #31296:
URL: https://github.com/apache/spark/pull/31296#discussion_r562868528
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File path: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
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@@ -2889,6 +2889,24 @@ class Dataset[T] private[sql](
flatMap(func)(encoder)
}
+ /**
+ * Return a new Dataset of string created by piping elements to a forked
external process.
+ * The resulting Dataset is computed by executing the given process once per
partition.
+ * All elements of each input partition are written to a process's stdin as
lines of input
+ * separated by a newline. The resulting partition consists of the process's
stdout output, with
+ * each line of stdout resulting in one element of the output partition. A
process is invoked
+ * even for empty partitions.
Review comment:
This sounds a little risky to me, `A process is invoked even for empty
partitions`.
This may cause a hang situation if the command is expecting input.
For example, this PR's test case is using `cat`. And, `cat | wc -l` hangs.
If you are okay, could you add a test case of empty partition to make it
sure that we handle those cases?
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