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https://issues.apache.org/jira/browse/SPARK-15051?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen updated SPARK-15051:
------------------------------
Assignee: kevin yu
> Aggregator with DataFrame does not allow Alias
> ----------------------------------------------
>
> Key: SPARK-15051
> URL: https://issues.apache.org/jira/browse/SPARK-15051
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Environment: Spark 2.0.0-SNAPSHOT
> Reporter: koert kuipers
> Assignee: kevin yu
> Fix For: 2.0.0
>
>
> this works:
> {noformat}
> object SimpleSum extends Aggregator[Row, Int, Int] {
> def zero: Int = 0
> def reduce(b: Int, a: Row) = b + a.getInt(1)
> def merge(b1: Int, b2: Int) = b1 + b2
> def finish(b: Int) = b
> def bufferEncoder: Encoder[Int] = Encoders.scalaInt
> def outputEncoder: Encoder[Int] = Encoders.scalaInt
> }
> val df = List(("a", 1), ("a", 2), ("a", 3)).toDF("k", "v")
> df.groupBy("k").agg(SimpleSum.toColumn).show
> {noformat}
> but it breaks when i try to give the new column a name:
> {noformat}
> df.groupBy("k").agg(SimpleSum.toColumn as "b").show
> {noformat}
> the error is:
> {noformat}
> org.apache.spark.sql.AnalysisException: unresolved operator 'Aggregate
> [k#192], [k#192,(SimpleSum(unknown),mode=Complete,isDistinct=false) AS b#200];
> at
> org.apache.spark.sql.catalyst.analysis.CheckAnalysis$class.failAnalysis(CheckAnalysis.scala:39)
> at
> org.apache.spark.sql.catalyst.analysis.Analyzer.failAnalysis(Analyzer.scala:54)
> at
> org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1.apply(CheckAnalysis.scala:270)
> at
> org.apache.spark.sql.catalyst.analysis.CheckAnalysis$$anonfun$checkAnalysis$1.apply(CheckAnalysis.scala:51)
> at
> org.apache.spark.sql.catalyst.trees.TreeNode.foreachUp(TreeNode.scala:125)
> at
> org.apache.spark.sql.catalyst.analysis.CheckAnalysis$class.checkAnalysis(CheckAnalysis.scala:51)
> at
> org.apache.spark.sql.catalyst.analysis.Analyzer.checkAnalysis(Analyzer.scala:54)
> at
> org.apache.spark.sql.execution.QueryExecution.assertAnalyzed(QueryExecution.scala:48)
> at org.apache.spark.sql.Dataset$.ofRows(Dataset.scala:61)
> {noformat}
> the reason it breaks is because Column.as(alias: String) returns a Column not
> a TypedColumn, and as a result the method TypedColumn.withInputType does not
> get called.
> P.S. The whole TypedColumn.withInputType seems actually rather fragile to me.
> I wish Aggregators simply also kept the input encoder and that whole bit can
> be removed about dynamically trying to insert the Encoder.
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