[jira] [Commented] (SPARK-25371) Vector Assembler with no input columns leads to opaque error

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-25371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16608443#comment-16608443 ] 

Apache Spark commented on SPARK-25371:
--------------------------------------

User 'mgaido91' has created a pull request for this issue:
https://github.com/apache/spark/pull/22373

> Vector Assembler with no input columns leads to opaque error
> ------------------------------------------------------------
>
>                 Key: SPARK-25371
>                 URL: https://issues.apache.org/jira/browse/SPARK-25371
>             Project: Spark
>          Issue Type: Bug
>          Components: ML, MLlib
>    Affects Versions: 2.3.0, 2.3.1
>            Reporter: Victor Alor
>            Priority: Trivial
>
> When `VectorAssembler ` is given an empty array as its inputColumns it throws an opaque error. In versions less than 2.3 `VectorAssembler` it simply appends a column containing empty vectors. 
>  
> {code:java}
> val inputCols = Array()
> val outputCols = Array("A")
> val vectorAssembler = new VectorAssembler()
> .setInputCols(inputCols)
> .setOutputCol(outputCols)
> vectorAssmbler.fit(data).transform(df)
> {code}
> In versions 2.3 > this throws the exception below
> {code:java}
> org.apache.spark.sql.AnalysisException: cannot resolve 'named_struct()' due to data type mismatch: input to function named_struct requires at least one argument;;
> {code}
> Whereas in versions less than 2.3 it just adds a column containing an empty vector.
> I'm not certain if this is an intentional choice or an actual bug. If this is a bug, the `VectorAssembler` should be modified to append an empty vector column if it detects no inputCols.
>  
> If it is a design decision it would be nice to throw a human readable exception explicitly stating inputColumns must not be empty. The current error is somewhat opaque.



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