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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