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Posted to issues@spark.apache.org by "L. C. Hsieh (Jira)" <ji...@apache.org> on 2020/03/15 21:43:00 UTC
[jira] [Updated] (SPARK-30983) Support more than 5 typed column in
typed Dataset.select API
[ https://issues.apache.org/jira/browse/SPARK-30983?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
L. C. Hsieh updated SPARK-30983:
--------------------------------
Description:
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. It can be a breaking change to existing user code that calls untyped select API.
was:
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.
> 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
> Priority: Major
>
> 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. It can be a breaking change to existing user code that calls untyped select API.
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