Over the years I've written a number of articles about SQL joins, including most recently the article Choosing the Right SQL Join. But what if your data wasn't stored in a database at all, instead spread across HTML, PDF, or Microsoft Word files, or worse, a combination of multiple file formats? Or consider a project to create a specialized search engine that would comb the most prominent corporate and research websites associated with the pharmaceutical or aeronautical industry? Indexing and searching data of this nature is no small feat, yet it remains a commonplace computing task.
Thankfully, as is often the case with common yet complex computing problems, chances are an open source project exists which at least lowers some of the "implementational" barriers. As it happens, a fantastic open source indexing and search library named Lucene offers developers a powerful tool for sifting through extraordinarily large data repositories while managing to be relatively simple to implement (particularly in a small office environment). In this article, I'll introduce you to Lucene, explaining how to install and configure it so you can begin searching data in entirely new ways.
Lucene is written in Java (although quite a few other language-specific ports exist), therefore it is supported on all of the major operating systems, Windows included. To install Lucene, download the latest stable binary version and extract the download to a convenient location. You'll also want to install Apache Ant. We'll use Ant to build the demo which is bundled with the Lucene download. You also have the option of downloading the Lucene source and building it using Ant; if you choose this approach be sure to read the
BUILD.txt file bundled with the source download.
With Lucene downloaded and Ant installed, you'll next need to add two JAR files to your
lucene-core-3.2.0.jar, which resides in the Lucene download's root directory, and
lucene-demo-3.2.0.jar, which resides in the Lucene download's
contrib/demo directory. Exactly how you go about modifying the
CLASSPATH variable is operating system-specific, so be sure to consult the Java documentation if you are unsure how to do so.
Running the Lucene Indexing and Searching Demo
CLASSPATH modified, execute the following command, pointing the
-docs argument to the directory you'd like to index.
$ java org.apache.lucene.demo.IndexFiles -docs /PATH/TO/FILE/REPOSITORY Indexing to directory 'index'... adding /home/wjgilmore/Downloads/zf1112/INSTALL.txt adding /home/wjgilmore/Downloads/zf1112/LICENSE.txt adding /home/wjgilmore/Downloads/zf1112/README.txt ... adding /home/wjgilmore/Downloads/zf1112/library/Zend/Text/Table/Column.php adding /home/wjgilmore/Downloads/zf1112/bin/zf adding /home/wjgilmore/Downloads/zf1112/bin/zf.php adding /home/wjgilmore/Downloads/zf1112/bin/zf.bat 12365 total milliseconds
Lucene will immediately begin the indexing process, recursively indexing every file in the directory and saving the index to a directory named
index, which is located within the current directory (you can change the directory location using the
-index argument). Once complete you can search the index by executing the
org.apache.lucene.demo.SearchFiles JAR. In the following example I'm searching the Zend Framework source code for the term
$ java org.apache.lucene.demo.SearchFiles Enter query: WindowsAzure Searching for: windowsazure 45 total matching documents 1. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationDataSources.php 2. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Storage/PageRegionInstance.php 3. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/PerformanceCounterSubscription.php 4. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/RetryPolicy/RetryPolicyAbstract.php 5. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationWindowsEventLog.php 6. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationPerformanceCounters.php 7. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationLogs.php 8. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationDiagnosticInfrastructureLogs.php 9. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Diagnostics/ConfigurationDirectories.php 10. /home/wjgilmore/Downloads/zf1112/library/Zend/Service/WindowsAzure/Credentials/Exception.php Press (n)ext page, (q)uit or enter number to jump to a page.