override def columnMapForWriting()

in driver/src/main/scala/com/datastax/spark/connector/mapper/TupleColumnMapper.scala [51:87]
30 lines of code
11 McCabe index (conditional complexity)

  override def columnMapForWriting(struct: StructDef, selectedColumns: IndexedSeq[ColumnRef]) = {
    val GetterRegex = "_([0-9]+)".r

    require(
      selectedColumns.forall(colName => colName.selectedAs == colName.columnName) ||
        selectedColumns.forall(colName => colName.selectedAs != colName.columnName),
      """No mixing of implicit and explicit column mapping when writing tuples
        |1. All columns must be un-aliased or aliased to themselves OR
        |2. Some columns aliased to fields (_1,_2 ...) but no columns are implicitly mapped"""
        .stripMargin
    )

    for (colName <- selectedColumns) {
      val columnName = colName.columnName
      val alias = colName.selectedAs
      if (alias != columnName && !methodNames.contains(alias))
        throw new IllegalArgumentException(
          s"""Found Alias: $alias
             |Tuple provided does not have a getter for that alias.'
             |Provided getters are ${methodNames.mkString(",")}""".stripMargin)
    }

    val aliasToRef = selectedColumns.map(colRef => colRef.selectedAs -> colRef).toMap

    //Implicit Mapping, Order of C* Columns == Tuple Field Order
    val getters = if (selectedColumns.forall(colRef => colRef.columnName == colRef.selectedAs)) {
      for (methodName @ GetterRegex(id) <- methodNames if id.toInt <= selectedColumns.length)
        yield (methodName, selectedColumns(id.toInt - 1))
    }.toMap
    else {
      //Explicit Mapping, Tuple field aliases used
      for (methodName @ GetterRegex(id) <- methodNames if aliasToRef.contains(methodName))
        yield (methodName, aliasToRef(methodName))
    }.toMap

    SimpleColumnMapForWriting(getters)
  }