Github user aokolnychyi commented on a diff in the pull request:
https://github.com/apache/spark/pull/16329#discussion_r93395745
--- Diff: docs/sql-programming-guide.md ---
@@ -382,6 +382,52 @@ For example:
</div>
+## Aggregations
+
+The [built-in DataFrames
functions](api/scala/index.html#org.apache.spark.sql.functions$) mentioned
+before provide such common aggregations as `count()`, `countDistinct()`,
`avg()`, `max()`, `min()`, etc.
+While those functions are designed for DataFrames, Spark SQL also has
type-safe versions for some of them in
+[Scala](api/scala/index.html#org.apache.spark.sql.expressions.scalalang.typed$)
and
+[Java](api/java/org/apache/spark/sql/expressions/javalang/typed.html) to
work with strongly typed Datasets.
+Moreover, users are not limited to the predefined aggregate functions and
can create their own.
--- End diff --
I also thought about this. In my view, it will be appropriate to have a
separate subsection before Aggregations to show how to apply predefined SQL
functions, including writing your own UDFs. That's will be worth another pull
request. Alternatively, I can also try to extend this one to add an example of
`max()` or `min()`. @marmbrus what's your opinion?
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
