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Posted to issues@spark.apache.org by "L. C. Hsieh (Jira)" <ji...@apache.org> on 2020/02/28 07:32:00 UTC
[jira] [Created] (SPARK-30983) Support more than 5 typed column in
typed Dataset.select API
L. C. Hsieh created SPARK-30983:
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Summary: Support more than 5 typed column in typed Dataset.select API
Key: SPARK-30983
URL: https://issues.apache.org/jira/browse/SPARK-30983
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.0.0
Reporter: L. C. Hsieh
Because Dataset only provides overloading typed select API to at most 5 typed columns, once more than 5 typed columns given, the select API call will go for untyped one.
Currently users cannot call typed select with more than 5 typed columns. There are few options:
1. Expose Dataset.selectUntyped (could rename it) to accept any number (due to the limit of ExpressionEncoder.tuple, at most 22 actually) of typed columns. Pros: not need to add too much code in Dataset. Cons: The returned type is generally Dataset[_], not a specified one like Dataset[(U1, U2)] for the overloading method.
2. Add more overloading typed select APIs up to 22 typed column inputs. Pros: Clear returned type. Cons: A lot of code to be added to Dataset for just corner cases.
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