filter only not empty arrays dataframe spark [duplicate]

Question

How can i filter only not empty arrays

import  org.apache.spark.sql.types.ArrayType

  val arrayFields = secondDF.schema.filter(st => st.dataType.isInstanceOf[ArrayType])
  val names = arrayFields.map(_.name)

Or is this code

val DF1=DF.select(col("key"),explode(col("objectiveAttachment")).as("collection")).select(col("collection.*"),col("key"))

|-- objectiveAttachment: array (nullable = true) 
 | |-- element: string (containsNull = true) 

I get this error

 org.apache.spark.sql.AnalysisException: Can only star expand struct data types. Attribute: ArrayBuffer(collection);

Any help is appreciated.

Answer 1

Use the function size

import org.apache.spark.sql.functions._

secondDF.filter(size($"objectiveAttachment") > 0)

Answer 2

Try with size() function from org.apache.spark.sql.functions._

    import org.apache.spark.sql.functions._
    val df1=df.select(col("key"),explode(col("objectiveAttachment")).as("collection")).select(col("collection.*"),col("ins"))
.filter(size($"objectiveAttachment")>0)