brandondahler commented on a change in pull request #33323:
URL: https://github.com/apache/spark/pull/33323#discussion_r689567804
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File path: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
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@@ -970,7 +995,59 @@ class Dataset[T] private[sql](
}
/**
- * Equi-join with another `DataFrame` using the given columns. A cross join
with a predicate
+ * Equi-join with another `DataFrame` using the given column. A cross join
with a predicate
+ * is specified as an inner join. If you would explicitly like to perform a
cross join use the
+ * `crossJoin` method.
+ *
+ * Different from other join functions, the join column will only appear
once in the output,
+ * i.e. similar to SQL's `JOIN USING` syntax.
+ *
+ * @param right Right side of the join operation.
+ * @param usingColumn Name of the column to join on. This column must exist
on both sides.
+ * @param joinType Type of join to perform. Default `inner`. Must be one of:
+ * `inner`, `cross`, `outer`, `full`, `fullouter`,
`full_outer`, `left`,
+ * `leftouter`, `left_outer`, `right`, `rightouter`,
`right_outer`,
+ * `semi`, `leftsemi`, `left_semi`, `anti`, `leftanti`,
left_anti`.
+ *
+ * @note If you perform a self-join using this function without aliasing the
input
+ * `DataFrame`s, you will NOT be able to reference any columns after the
join, since
+ * there is no way to disambiguate which side of the join you would like to
reference.
+ *
+ * @group untypedrel
+ * @since 3.3.0
+ */
+ def join(right: Dataset[_], usingColumn: String, joinType: String):
DataFrame = {
+ join(right, Seq(usingColumn), joinType)
+ }
+
+ /**
+ * (Java-specific) Equi-join with another `DataFrame` using the given
columns. A cross join with
Review comment:
I'm not familiar with scala in general and I tried to mess with
Scaladoc's `@see` link formatting, but I wasn't able to successfully get it to
actually link to the other overloaded method.
I used these links for reference and did various different formats as
suggested, but IntelliJ doesn't seem to accept them (presuming that the
IntelliJ implementation correctly processes them):
* https://docs.scala-lang.org/overviews/scaladoc/for-library-authors.html
* https://stackoverflow.com/questions/53850885/how-to-use-see-scaladoc
*
https://github.com/scala/scala/blob/2.12.x/test/scaladoc/resources/links.scala
I'm happy to make the change if anyone knows the correct syntax for
referring from `Dataset#join(Dataset[_], Array[String], String): DataFrame` to
`Dataset#join(Dataset[_], Seq[String], String): DataFrame)`.
---
All that being said, as a user of the library I'd prefer the docs not
require an extra level of indirection in this case because there's not really
that much information being expressed in these docs -- the biggest section in
it is the `@param joinType` and that's only because it is listing out all the
valid values.
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