[jira] [Created] (SPARK-40830) Dataset.groupBy.as should be preferred over Dataset.groupByKey

["Enrico Minack (Jira)" <ji...@apache.org>]

Enrico Minack created SPARK-40830:
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             Summary: Dataset.groupBy.as should be preferred over Dataset.groupByKey
                 Key: SPARK-40830
                 URL: https://issues.apache.org/jira/browse/SPARK-40830
             Project: Spark
          Issue Type: Improvement
          Components: Documentation, SQL
    Affects Versions: 3.4.0
            Reporter: Enrico Minack


Calling {{Dataset.groupBy(...).as[K, T]}} should be preferred over calling {{Dataset.groupByKey(...)}} whenever possible. The former allows Catalyst to exploit existing partitioning and ordering of the Dataset, while the latter hides the columns used to create the keys from Catalyst.

Example:

Calling {{ds.groupByKey(_.id)}} hides from Catalyst that column id is the grouping key.
With {{ds.groupBy($"id").as[Int, V]}} tells Catalyst that {{ds}} is to be grouped by (partitioned and ordered by) column "id".

This fact should be documented. Further, {{groupByKey}} methods with {{Column}} and {{String}} arguments would help to short cut {{groupByKey.as}} and avoid the {{groupBy(func)}} methods.



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