private VectorizedRowBatch getBatchLongDecimal() {
    VectorizedRowBatch b = new VectorizedRowBatch(2);
    LongColumnVector lv;
    b.cols[0] = lv = new LongColumnVector();
    b.cols[1] = new DecimalColumnVector(18, 2);
    lv.vector[0] = 0;
    lv.vector[1] = -1;
    lv.vector[2] = 99999999999999L;
    return b;
  }
Just spot check the basic case because code path is the same as
for cast of decimal to long due to inheritance.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/expressions/TestVectorTypeCasts.java