private VectorizedRowBatch getBatchLongDecimalPrec5Scale2() {
    VectorizedRowBatch b = new VectorizedRowBatch(2);
    LongColumnVector lv;
    b.cols[0] = lv = new LongColumnVector();
    b.cols[1] = new DecimalColumnVector(5, 2);
    lv.vector[0] = 0;
    lv.vector[1] = -1;
    lv.vector[2] = 99999999999999L;
    return b;
  }
This batch has output decimal column precision 5 and scale 2.
The goal is to allow testing of input long values that, when
converted to decimal, will not fit in the given precision.
Then it will be possible to check that the results are NULL.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/expressions/TestVectorTypeCasts.java