Java 示例：重载 UDx

// You need to specify the full package when creating functions based on
// the classes in your library.
package com.mycompany.multiparamexample;
// Import the entire Vertica SDK
import com.vertica.sdk.*;
// This ScalarFunction accepts two or three integer arguments. It tests
// the number of input columns to determine whether to read two or three
// arguments as input.
public class Add2or3ints extends ScalarFunction
{
    @Override
    public void processBlock(ServerInterface srvInterface,
                             BlockReader argReader,
                             BlockWriter resWriter)
                throws UdfException, DestroyInvocation
    {
        // See how many arguments were passed in
        int numCols = argReader.getNumCols();

        // Return an error if less than two or more than 3 aerguments
        // were given. This error only occurs if a Factory class that
        // accepts the wrong number of arguments instantiates this
        // class.
        if (numCols < 2 || numCols > 3) {
            throw new UdfException(0,
                "Must supply 2 or 3 integer arguments");
        }

        // Process all of the rows of input.
        do {
            // Get the first two integer arguments from the BlockReader
            long a = argReader.getLong(0);
            long b = argReader.getLong(1);

            // Assume no third argument.
            long c = 0;

            // Get third argument value if it exists
            if (numCols == 3) {
                c = argReader.getLong(2);
            }

            // Process the arguments and come up with a result. For this
            // example, just add the three arguments together.
            long result = a+b+c;

            // Write the integer output value.
            resWriter.setLong(result);

            // Advance the output BlocKWriter to the next row.
            resWriter.next();

            // Continue processing input rows until there are no more.
        } while (argReader.next());
    }
}

// You will need to specify the full package when creating functions based on
// the classes in your library.
package com.mycompany.multiparamexample;
// Import the entire Vertica SDK
import com.vertica.sdk.*;
public class Add2intsFactory extends ScalarFunctionFactory
{
    @Override
    public void getPrototype(ServerInterface srvInterface,
                             ColumnTypes argTypes,
                             ColumnTypes returnType)
    {
        // Accept two integers as input
        argTypes.addInt();
        argTypes.addInt();
        // writes one integer as output
        returnType.addInt();
    }
    @Override
    public ScalarFunction createScalarFunction(ServerInterface srvInterface)
    {
        // Instantiate the class that can handle either 2 or 3 integers.
        return new Add2or3ints();
    }
}

// You will need to specify the full package when creating functions based on
// the classes in your library.
package com.mycompany.multiparamexample;
// Import the entire Vertica SDK
import com.vertica.sdk.*;
public class Add3intsFactory extends ScalarFunctionFactory
{
    @Override
    public void getPrototype(ServerInterface srvInterface,
                             ColumnTypes argTypes,
                             ColumnTypes returnType)
    {
        // Accepts three integers as input
        argTypes.addInt();
        argTypes.addInt();
        argTypes.addInt();
        // Returns a single integer
        returnType.addInt();
    }
    @Override
    public ScalarFunction createScalarFunction(ServerInterface srvInterface)
    {
        // Instantiates the Add2or3ints ScalarFunction class, which is able to
        // handle eitehr 2 or 3 integers as arguments.
        return new Add2or3ints();
    }
}