Handling Java UDx Dependencies

If your Java UDx relies on one or more external libraries, you can handle the dependencies in one of three ways:

• Bundle the JAR files into your UDx JAR file using a tool such as One-JAR or Eclipse Runnable JAR Export Wizard.
• Unpack the JAR file and then repack its contents in your UDx's JAR file.

• Copy the libraries to your Vertica cluster in addition to your UDx library.Then, use the DEPENDS keyword of the CREATE LIBRARY statement to tell Vertica that the UDx library depends on the external libraries. This keyword acts as a library-specific CLASSPATH setting. Vertica distributes the support libraries to all of the nodes in the cluster and sets the class path for the UDx so it can find them.

  If your UDx depends on native libraries (SO files), use the DEPENDS keyword to specify their path. When you call System.loadLibrary in your UDx (which you must do before using a native library), this function uses the DEPENDS path to find them. You do not need to also set the LD_LIBRARY_PATH environment variable.

External Library Example

The following example demonstrates using an external library with a Java UDx.

The following sample code defines a simple class, named VowelRemover. It contains a single method, named removevowels, that removes all of the vowels (the letters a, e, i, o u, and y) from a string.

package com.mycompany.libs;

public class VowelRemover {
	public String removevowels(String input) {
		return input.replaceAll("(?i)[aeiouy]", "");
	}
};

You can compile this class and package it into a JAR file with the following commands:

$ javac -g com/mycompany/libs/VowelRemover.java
$ jar cf mycompanylibs.jar com/mycompany/libs/VowelRemover.class

The following code defines a Java UDSF, named DeleteVowels, that uses the library defined in the preceding example code. DeleteVowels accepts a single VARCHAR as input, and returns a VARCHAR.

package com.mycompany.udx;
// Import the support class created earlier
import com.mycompany.libs.VowelRemover;
// Import the Vertica SDK
import com.vertica.sdk.*;

public class DeleteVowelsFactory extends ScalarFunctionFactory {

    @Override
    public ScalarFunction createScalarFunction(ServerInterface arg0) {
        return new DeleteVowels();
    }

    @Override
    public void getPrototype(ServerInterface arg0, ColumnTypes argTypes,
            ColumnTypes returnTypes) {
        // Accept a single string and return a single string.
        argTypes.addVarchar();
        returnTypes.addVarchar();
    }
    
    @Override
    public void getReturnType(ServerInterface srvInterface,
            SizedColumnTypes argTypes,
            SizedColumnTypes returnType){
        returnType.addVarchar(
        // Output will be no larger than the input.
        argTypes.getColumnType(0).getStringLength(), "RemovedVowels");
    }
    
    public class DeleteVowels extends ScalarFunction
    {
        @Override
        public void processBlock(ServerInterface arg0, BlockReader argReader,
                BlockWriter resWriter) throws UdfException, DestroyInvocation {
            
            // Create an instance of the  VowelRemover object defined in 
            // the library.
            VowelRemover remover = new VowelRemover();
            
            do {
                String instr = argReader.getString(0);
                // Call the removevowels method defined in the library.
                resWriter.setString(remover.removevowels(instr));
                resWriter.next();
            } while (argReader.next());
        }
    }

}

Use the following commands to build the example UDSF and package it into a JAR:

• The first javac command compiles the SDK’s BuildInfo class. Vertica requires all UDx libraries to contain this class. The javac command’s -d option outputs the class file in the directory structure of your UDSF’s source.
• The second javac command compiles the UDSF class. It adds the previously-created mycompanylibs.jar file to the class path so compiler can find the the VowelRemover class.
• The jar command packages the BuildInfo and the classes for the UDx library together.

$ javac -g -cp /opt/vertica/bin/VerticaSDK.jar\
   /opt/vertica/sdk/com/vertica/sdk/BuildInfo.java -d .
$ javac -g -cp mycompanylibs.jar:/opt/vertica/bin/VerticaSDK.jar\
  com/mycompany/udx/DeleteVowelsFactory.java
$ jar cf DeleteVowelsLib.jar com/mycompany/udx/*.class \
   com/vertica/sdk/*.class

To install the UDx library, you must copy both of the JAR files to a node in the Vertica cluster. Then, connect to the node to execute the CREATE LIBRARY statement.

The following example demonstrates how to load the UDx library after you copy the JAR files to the home directory of the dbadmin user. The DEPENDS keyword tells Vertica that the UDx library depends on the mycompanylibs.jar file.

=> CREATE LIBRARY DeleteVowelsLib AS 
   '/home/dbadmin/DeleteVowelsLib.jar' DEPENDS '/home/dbadmin/mycompanylibs.jar' 
   LANGUAGE 'JAVA';
CREATE LIBRARY
=> CREATE FUNCTION deleteVowels AS language 'java' NAME 
  'com.mycompany.udx.DeleteVowelsFactory' LIBRARY DeleteVowelsLib;
CREATE FUNCTION
=> SELECT deleteVowels('I hate vowels!');
 deleteVowels
--------------
  ht vwls!
(1 row)