Github user viirya commented on a diff in the pull request: https://github.com/apache/spark/pull/23045#discussion_r233873941 --- Diff: docs/sql-migration-guide-upgrade.md --- @@ -17,6 +17,8 @@ displayTitle: Spark SQL Upgrading Guide - The `ADD JAR` command previously returned a result set with the single value 0. It now returns an empty result set. + - In Spark version 2.4 and earlier, users can create map values with map type key via built-in function like `CreateMap`, `MapFromArrays`, etc. Since Spark 3.0, it's not allowed to create map values with map type key. + --- End diff -- I think should we also add this note? > Note that, maps with map type key still exist, via reading from parquet files, converting from scala/java map, etc. Spark is not to completely forbid map as map key, but to avoid creating it by Spark itself.
--- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org