PolymorphicVectors.scala

trait ValueVector {
  def allocateNew()
}

abstract class BaseFixedWidthVector extends ValueVector {
  def allocateNew() {
    // impl
  }
}

class IntVector extends BaseFixedWidthVector

abstract class BaseVariableWidthVector extends ValueVector {
  def allocateNew() {
    // impl
  }
}

class VarCharVector extends BaseVariableWidthVector

val intVector: ValueVector = new IntVector()
val strVector: ValueVector = new VarCharVector()

intVector.allocateNew()
strVector.allocateNew()