public DataTypePhysicalVariation getDataTypePhysicalVariation(int columnNum) throws HiveException {
    if (initialDataTypePhysicalVariations == null) {
      return null;
    }
    if (columnNum < initialDataTypePhysicalVariations.size()) {
      return initialDataTypePhysicalVariations.get(columnNum);
    }
    return ocm.getDataTypePhysicalVariation(columnNum);
  }
Context class for vectorization execution.
Main role is to map column names to column indices and serves as a
factory class for building vectorized expressions out of descriptors.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizationContext.java