David Allsopp created SPARK-21459:
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Summary: Some aggregation functions change the case of nested
field names
Key: SPARK-21459
URL: https://issues.apache.org/jira/browse/SPARK-21459
Project: Spark
Issue Type: Bug
Components: Spark Core
Affects Versions: 1.6.0
Reporter: David Allsopp
Priority: Minor
When working with DataFrames with nested schemas, the behavior of the
aggregation functions is inconsistent with respect to preserving the case of
the nested field names.
For example, {{first()}} preserves the case of the field names, but
{{collect_set()}} and {{collect_list()}} force the field names to lowercase.
Expected behavior: Field name case is preserved (or is at least consistent and
documented)
Spark-shell session to reproduce:
{code:java}
scala> case class Inner(Key:String, Value:String)
scala> case class Outer(ID:Long, Pairs:Array[Inner])
val rdd = sc.parallelize(Seq(Outer(1L, Array(Inner("foo", "bar")))))
val df = sqlContext.createdataFrame(rdd)
scala> df
... = [ID: bigint, Pairs: array<struct<Key:string,Value:string>>]
scala>df.groupBy("ID").agg(first("Pairs"))
... = [ID: bigint, first(Pairs)(): array<struct<Key:string,Value:string>>]
// Note that Key and Value preserve their original case
scala>df.groupBy("ID").agg(collect_set("Pairs"))
... = [ID: bigint, collect_set(Pairs): array<struct<key:string,value:string>>]
// Note that key and value are now lowercased
{code}
Additionally, the column name is inconsistent: {{first(Pairs)()}} versus
{{collect_set(Pairs)}} - note the extra parentheses for in the first name.
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