HeartSaVioR commented on a change in pull request #28377:
URL: https://github.com/apache/spark/pull/28377#discussion_r416230700
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File path: sql/core/src/main/scala/org/apache/spark/sql/Column.scala
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@@ -1016,17 +1010,11 @@ class Column(val expr: Expression) extends Logging {
* df.select($"colA".name("colB"))
* }}}
*
- * If the current column has metadata associated with it, this metadata will
be propagated
- * to the new column. If this not desired, use `as` with explicitly empty
metadata.
Review comment:
I'd say the comment is slightly invalid as of now, depending on how we
interpret "propagation" here. If someone interprets propagation as a "copy"
then that becomes wrong. It's more likely that we leave it on the behavior of
Alias without touching.
And there're overloaded method which receives metadata, which may get rid of
necessity of explaining.
But yes that doesn't mean we need to remove these comments - that's also an
option we may reword a bit to try resolving ambiguity and keep leaving the part
of comment instead.
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