public static VectorExpressionWriter genVectorExpressionWritable(ExprNodeDesc nodeDesc)
      throws HiveException {
      ObjectInspector objectInspector = nodeDesc.getWritableObjectInspector();
      if (null == objectInspector) {
        objectInspector = TypeInfoUtils
            .getStandardWritableObjectInspectorFromTypeInfo(nodeDesc.getTypeInfo());
      }
      if (null == objectInspector) {
        throw new HiveException(String.format(
            "Failed to initialize VectorExpressionWriter for expr: %s",
            nodeDesc.getExprString()));
      }
      return genVectorExpressionWritable(objectInspector);
    }
Compiles the appropriate vector expression writer based on an expression info (ExprNodeDesc)
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorExpressionWriterFactory.java