Lucene in Action 109
Simon P. Chappell writes "I don't know about you, but I hardly bother with browser bookmarks any more. I used to have so many bookmarks, back in the early days of Netscape's 4 series, that I would have to regularly trim and edit my bookmark file to prevent my browser from crashing on startup -- that's a lot of bookmarks, folks! Now, I go to my favourite web search engine, enter a couple of appropriate search terms and voila, there's my page! Search engines are so ubiquitous that we rarely give much thought to the technology that powers them. Lucene in Action by Otis Gospodnetic and Erik Hatcher , both committers on the Lucene project, goes behind the HTML and takes you on a guided tour of Lucene, one of a generation of powerful Free and Open-Source search engines now available." Read on for the rest of Chappell's review.
Lucene in Action | |
author | Gospodnetic and Hatcher |
pages | 421 (7 pages of index) |
publisher | Manning |
rating | 9 |
reviewer | Simon P. Chappell |
ISBN | 1932394281 |
summary | Solid introduction to Lucene |
Who's it for?
Lucene is a library and framework, rather than a complete application. It truly is an engine, around which you are expected to build and extend your own application. Like Lucene, the book is targeted at those who are looking for a tool to build their own search facility application rather than just "download and go." The book does include a number of case studies of Lucene usage (including at least one download and go search engine) but those are included to show how to use and adapt Lucene to fit differing environments rather than as ends in themselves.The Structure
The book is sensibly divided into two parts. The first part looks at "Core Lucene" functionality, while the second part addresses "Applied Lucene".Part one has six chapters, covering the central components and inner workings of Lucene. It's here that the book starts with a tutorial introduction, familiarising the reader with the concepts of Lucene as a search engine around which you wrap your own code. The other five chapters move steadily through good search engine fare, with indexing getting the whole of chapter two to itself The discussion of how to retrieve text from the documents being indexed is mentioned here but postponed until chapter seven, where it is dealt with exhaustively. Chapter three covers searching, and especially how Lucene ranks documents.
Chapter four examines analysis. In it's chapter introduction, the book explains that "Analysis, in Lucene, is the process of converting field text into it's most fundamental indexed representation, terms." This process is performed by an analyser, which tokenises text according to it's own built in rules; each analyser will have a different emphasis, some want only dictionary words, others might explicitly include acronyms and sometimes you'll want an analyser that will block stop words (those words in languages that are part of the structure, but that add nothing to the information being conveyed by the text; classic examples of stop words in English include "a", "and" and "the").
Chapter five looks at advanced search techniques; everything from sorting search results, searching on multiple fields to filtering searches. Many free or open source software tools are extensible, and Lucene is no exception. Chapter six addresses creating and using custom components within Lucene, everything from custom sort methods to custom filters.
Part two, the final four chapters, cover Applied Lucene. It is dedicated to practical uses of Lucene and answers the question "So, what can I do with a search engine?" Chapter seven covers ways and means to parse common, non-plain text document formats. The primary formats covered are RTF, XML, PDF, HTML and Microsoft Word. The ability to parse and index these file formats will cover the search engine needs of the majority of Lucene users. Chapter eight looks at a number of Lucene tools and extensions that are available; many of them being free and open source software. Chapter nine covers ports of Lucene. While for many users, Lucene being a Java library is not a problem, some users want its functionality in environments that do not have Java. The chapter looks at ports written in C++, C#, Perl and Python. Lastly, chapter ten takes a thorough look at seven Lucene case studies. Perhaps the "star" case study is the one about Nutch, a download and go search engine written by Doug Cutting , the original author of Lucene.
There are three appendices. The first offers installation advice for Lucene; a useful addition that those newer to working with Java libraries will surely appreciate. The second appendix has a very well explained description of the Lucene index format. This is the kind of information that can be hard to find, so it is welcome in a book of this sort. The last appendix contains a number of categorised resource references. The number and breadth of the resources provided could provide quite an incredible education in information retrieval theory if the reader was inclined to read them all.
What's to Like?
There are several things to like about this book. Let's start with the fact that the authors are part of the core development team of Lucene. This gives them both credibility and an excellent understanding of the internal workings of Lucene. Co-author Erik Hatcher is a fantastic writer, having previously been a co-author of the only Ant book worth bothering with, Manning's Java Development with Ant . (Full disclosure: I do know Erik personally.)The structure of the book is well thought out and each chapter does seem to move your understanding forward when combined with what you learned from the proceeding ones. The division into core and applied Lucene is also helpful. While you'd hope that this was the case, it often isn't; hence I note it as a positive.
I especially appreciate that this book does not fill up page after page with API documentation. The authors appear to have grasped that if you have Internet access to download the software, you might just be able to access the documentation online; rather, they concentrate on the way to use the software. What a concept!
As a part of Manning's "in Action" series, the book has excellent layout and has obviously been thoroughly edited by both technical evaluators and copyeditors. This might seem to be a small thing to some, but a well-edited book stands out clearly from the crowd.
What's to consider?
If you are looking for a book on using and configuring a download and go style of search engine, this book would be less suitable. While the case study on Nutch is of good length, it would be too short to useful as a configuration guide.Conclusion
I enjoyed reading this book. If you have any text searching needs, this book will be more than sufficient equipment to guide you to successful completion. Even, if you are just looking to download a pre-written search engine, then this book will provide a good background to the nature of information retrieval in general and text indexing and searching specifically.You can purchase Lucene in Action from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
Re:Raise your hand if... (Score:3, Informative)
Re:Benefits? (Score:4, Informative)
Some examples of customizable features are that you can index database entries and achieve quantum leaps in performance over that offered by Oracle, MySQL, PostGres, Firebird, etc. indexing. You can index formats that are not supported by the major search enginges.
It may not offer quite the performance of Google, Alta Vista, etc., but it's a FREE product, well supported by the folks at Apache, and many open source J2EE frameworks support it as well.
Good article (Score:3, Informative)
This is also a good link for all of you slashdotters who have no idea what Lucene is for and are posting rants wondering why people don't just use Google instead.
my problem solver (Score:2, Informative)
Sitebar saved my sanity... (Score:3, Informative)
Usual disclaimer: I have nothing to do with Sitebar or its development, just a majorly satisfied user.
Try delicious? (Score:2, Informative)
If you use Firefox, there are extensions that allow you to view your bookmarks in a sidebar [mozdev.org] and sync your online bookmarks [ganx4.com] with your browser bookmarks.
Lucene in a nutshell (over-simplified) (Score:5, Informative)
The basic idea is that you want to build an index, and then search it, to find some document.
A document has several fields (e.g. text, title, lastModificationDate, author, categories, summary, url, etc.) which may be indexed, stored, or both.
You usually build your lucene documents, based on some real documents (e.g. web pages, PDF, records in a database, etc.), and then add them to the index.
Once you have an index, you build a query to search one or more fields (lucene provides a QueryParser class, which handles the most common cases), and you get a Hits collection containing the documents matching your query in some order (this can be customized).
Before a document is added to the index, it is passed through an Analyzer which converts the text in the fields to terms, which are the basic internal concept that is indexed.
Another interesting feature of lucene indexes is that they can be searched while they are being built without noticeable loss of search performance, and that they are process-safe (many processes can access them for reading, only one for writing), this has the drawback that the indexes are append-only (actually a separate index is created if you modify an index), but periodical optimization of the indexes removes unnecessary entries and inefficiencies.
Hope this helps!
juancn
Re:Google anyone ? (Score:4, Informative)
The best reason is that its very, very easy to set up a Google search... all you have to do is add site:your_site to the search query, and Bam! instant search.
Lucene takes some work to setup, and is best used where normal Web crawling doesn't work. For example, I work on an eCommerce Web App where all our products are stored in the database, and you reach them by setting a CGI parameter in the URL. Not all products have links to them on our site. We use Lucene because we can pull all the products out of the database and index them, and get hits that crawling would have missed. We can also customize things like redirecting a search for "help" to the help page, set up synonym lists, etc.
So long story short, their search needs are not complex enough to justify the effort of setting up a Lucene based application.
Lucene is great! I use it all the time (Score:4, Informative)
http://www.devx.com/Java/Article/27728/0 [devx.com]
Lucene is so well documented and simple to use that I am surprised that this subject would fill an entire book
Lucene can be used as is, or you can extend it with your own document type handlers, etc.
As a programmer, I way prefer dynamic languages like Common Lisp, Ruby, Python, Smalltalk, etc. However, one of the things that keeps me firmly in the "Java camp" is the great free infrastructure software tools (like Lucene, Tomcat, JBoss, etc.) As a programming language, Java is kind-of weak.
Lucene rocks! (Score:2, Informative)
And you can index pretty much anything you want, so long as you can get it into a string. Everyone knows you can index documents in XML, HTML, etc, but you can also index objects with strings, integers and dates, hash tables and lists. Just put a primary key value and a table name and you can retrieve the full object from your database. Very cool indeed.
Every programmer out there with skills in relational databases should take a look at a information retrieval library like lucene. It's a completely different field from relational databases and it will change how you think about storing and searching data. It's not a replacement for relational databases, but it does complement them very well and allows you to do things that you wouldn't normally be able to do, like allowing for results that partially match the search query, and being able to rank them by relevance.
del.icio.us is better (Score:3, Informative)
I find bookmarks slow to navigate, and it's hard for me to remember my own hierarchy when I've got enough bookmarks to organize. The problems with search have been expanded on by others in this thread.
So here's the solution: http://del.icio.us/ [icios.us].
You can create, edit, tag, describe, and search your own personal bookmarks. When you've done that, the world can see your links too. Subscribing to an RSS feed of some tags you're interested in ("python" for me) gives you a constant stream of interesting links other people who are into Python found useful.
If you're using Firefox, you'll probably want del.icio.us in your search box. Find that here [mozdev.org] . I find myself frequently using this when I'd normally use Google, when I know (or just suspect) that I've been somewhere before.
What I've been doing for about a year now is keeping my actual in-browser bookmarks an unsorted flat list with just about 20 sites I visit on a regular basis. Webcomics, blogs that don't have RSS feeds already, and the like. Everything else goes into del.icio.us. All my other bookmarks were of one of these categories: links I visit only occasionally for reference, sites I intended to visit just once later when I have free time, or sites that I don't even know if I'll find useful until I go back and reread them. Now I don't have to clutter my browser with those; I throw them in del.icio.us. As a bonus, del.icio.us tells you how many other people have bookmarked the page. Number of times a link is being submitted is a good first-blush indication of whether the information there is really interesting or useful.
Re:PyLucene (Score:2, Informative)
Just thought I'd pipe in... (Score:3, Informative)
- Good ways of doing batch indexing operations
- The purpose of the compound document format
- How to generate explainers for searches
- Field-specific handling, and how to do it well
- Ideas like metaphone replacement (soundex) and use of WordNet to integrate a synonym database into search queries
- When to use CachedFilters to remember complex filters
- Ideas for how to build "Things Like This" lists
- Ideas on autocategorisation and geographic searches
- Named Entities and LingPipe - making the search system recognize "proper names" for things
- NGRAM recording to gauge word frequency and search terms to detect misspellings and offer alternate searches ("Did you mean XXX"?)
etc.
If you're building a search engine, this isn't just a useful resource on implementation - you probably don't need a book for that. What it is brilliant at is providing a lot of ideas that can take you to the next stage - how to build something really cool with your information, and not just a dumb text field search.
For that alone, the book was worth the purchase price, for me. It's now well annotated, and the back pages are full of references to ideas that can be used in our own implementation, and the page numbers to use to get there.
Highly recommended for anyone who needs something more than what a Google search of your site provides.