private VectorizedRowBatch getBatchStringDecimal() {
    VectorizedRowBatch b = new VectorizedRowBatch(2);
    BytesColumnVector bv;
    b.cols[0] = bv = new BytesColumnVector();
    b.cols[1] = new DecimalColumnVector(18, 2);

    bv.initBuffer();

    byte[] x0 = toBytes("1.10");
    byte[] x1 = toBytes("-2.20");
    byte[] x2 = toBytes("99999999999999.0");

    bv.setVal(0, x0, 0, x0.length);
    bv.setVal(1, x1, 0, x1.length);
    bv.setVal(2, x2, 0, x2.length);

    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