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https://issues.apache.org/jira/browse/SPARK-25371?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Victor Alor updated SPARK-25371:
--------------------------------
    Description: 
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.

  was:
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.


> Vector Assembler with no input columns throws an exception
> ----------------------------------------------------------
>
>                 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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