Java example: AddAnyInts

The following example shows an implementation of a Java ScalarFunction that adds together two or more integers.

For the complete source code, see AddAnyIntsInfo.java in the examples (in /opt/vertica/sdk/examples/JavaUDx/ScalarFunctions).

Loading and using the example

Load the library and create the function as follows:

=> CREATE LIBRARY JavaScalarFunctions AS '/home/dbadmin/JavaScalarLib.jar' LANGUAGE 'JAVA';
CREATE LIBRARY

=> CREATE FUNCTION addAnyInts AS LANGUAGE 'Java' NAME 'com.vertica.JavaLibs.AddAnyIntsInfo'
   LIBRARY JavaScalarFunctions;
CREATE FUNCTION

Call the function with two or more integer arguments:

=> SELECT addAnyInts(1,2);
 addAnyInts
------------
          3
(1 row)

=> SELECT addAnyInts(1,2,3,40,50,60,70,80,900);
 addAnyInts
------------
       1206
(1 row)

Calling the function with too few arguments, or with non-integer arguments, produces errors that are generated from the processBlock() method. It is up to your UDx to ensure that the user supplies the correct number and types of arguments to your function and exit with an error if it cannot process them.

Function implementation

Most of the work in the example is done by the processBlock() method. It performs two checks on the arguments that have been passed in through the BlockReader object:

• There are at least two arguments.

• The data types of all arguments are integers.

It is up to your polymorphic UDx to determine that all of the input passed to it is valid.

Once the processBlock() method validates its arguments, it loops over them, adding them together.

        @Override
        public void processBlock(ServerInterface srvInterface,
                                 BlockReader arg_reader,
                                 BlockWriter res_writer)
                    throws UdfException, DestroyInvocation
        {
        SizedColumnTypes inTypes = arg_reader.getTypeMetaData();
        ArrayList<Integer> argCols = new ArrayList<Integer>(); // Argument column indexes.
        inTypes.getArgumentColumns(argCols);
        // While we have inputs to process
            do {
        long sum = 0;
        for (int i = 0; i < argCols.size(); ++i){
            long a = arg_reader.getLong(i);
            sum += a;
        }
                res_writer.setLong(sum);
                res_writer.next();
            } while (arg_reader.next());
        }
    }

Factory implementation

The factory declares the number and type of arguments in the getPrototype() function.

    @Override
    public void getPrototype(ServerInterface srvInterface,
                             ColumnTypes argTypes,
                             ColumnTypes returnType)
    {
    argTypes.addAny();
        returnType.addInt();
    }