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Posted to reviews@spark.apache.org by GitBox <gi...@apache.org> on 2020/02/20 04:30:43 UTC
[GitHub] [spark] gatorsmile commented on a change in pull request #27621:
[SPARK-26071][followup] Improve migration guide of disallowing map type map
key
gatorsmile commented on a change in pull request #27621: [SPARK-26071][followup] Improve migration guide of disallowing map type map key
URL: https://github.com/apache/spark/pull/27621#discussion_r381740913
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File path: docs/sql-migration-guide.md
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@@ -43,7 +43,7 @@ license: |
- 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 with these built-in functions. Users can still read map values with map type key from data source or Java/Scala collections, though they are not very useful.
+ - In Spark version 2.4 and earlier, users can create map values with map type key via built-in function such as `CreateMap`, `MapFromArrays`, etc. Since Spark 3.0, it's not allowed to create map values with map type key with these built-in functions. Users can use array<struct<key, value>> as map keys instead as a workaround. In addition, users can still read map values with map type key from data source or Java/Scala collections, though it is discouraged.
Review comment:
Could we give a very simple example, how to use array<struct<key, value>> as map keys as a workaround? Also, do we have such a test case?
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