Consider the search query "Main Memory" it searches for all 4 words individually and the result would be like,. The result would be File1 followed by File2. To stop getting carried away by weights on most common words like 'and', 'or', 'the' it considers the inverse document frequency ie' it decreases the weight of the word which is most popular among the document set. How are we doing? Please help us improve Stack Overflow. Take our short survey. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How does Lucene work Ask Question. Asked 11 years, 6 months ago. Active 3 years, 4 months ago. Viewed 38k times. Improve this question. Midhat Midhat Can I request this question to be converted as a community wiki?
Lucene sounds like a platform now. Add a comment. Active Oldest Votes. Improve this answer. If I understand correctly, the thing that sets text search engines apart is how they handle multi-word searches and joining the results of searches to multiple indexes in real time. I would not suggest consulting Lucene source for this. It would probably be better to read a little about text search theory, alienCoder's answer helped me. This is not the place for whole-book answers. There are any number of elaborations on the basic concept in there.
What do you mean "an index for each word" An index B-tree from word to document can search for documents by words in the document because the table of such an index is word, document where the index is on the word column. Consider a query like: "Find documents with words 'police','crime','statistics'" in them.
By searching the word index, you can do three log N searches to get O N documents with one of those words in them. Then you can do two O N loops to build a set containing documents that have all three words. Skimmed over that paper, it was pretty helpful. Specifically "4. Apache Lucene Java. Pages Blog. Space shortcuts Meeting notes. Page tree. Browse pages. A t tachments 0 Page History People who can view. Copy Page Tree.
Pages Home Old Moin wiki. Jira links. How to make searching faster Here are some things to try to speed up the seaching speed of your Lucene application. Be sure you really need to speed things up. Many of the ideas here are simple to try, but others will necessarily add some complexity to your application. So be sure your searching speed is indeed too slow and the slowness is indeed within Lucene.
Make sure you are using the latest version of Lucene. Use a local filesystem. Remote filesystems are typically quite a bit slower for searching. If the index must be remote, try to mount the remote filesystem as a "readonly" mount. In some cases this could improve performance. Get faster hardware, especially a faster IO system. Flash-based Solid State Drives works very well for Lucene searches.
As seek-times for SSD's are about times faster than traditional platter-based harddrives, the usual penalty for seeking is virtually eliminated. This means that SSD-equipped machines need less RAM for file caching and that searchers require less warm-up time before they respond quickly. Complete query capability - The search technology encompasses everything from spell-checking proximity operators to enabling multi-lingual search. Holistic results - Lucene performs a full-result processing that includes relevancy-sorting, sorting using date or any given field and also dynamic summaries.
Probability - Lucene runs on just about any platform that is compatible with Java. What's more, its indexes are portable across platforms too. The fact that Lucene is an Apache open source software leverages a host of benefits to its end-users in terms of free use, independence and control one usually gets by writing software himself.
It also lets users produce and distribute derivates and proprietary work without any degree of restrictions, making it one of the most efficient, scalable and accurate technology. That being said, its limitations hover over the fact that there are no formal support contracts, no assured availability of training or formalized release of testing programs. Contact US. Happiest Minds enables Digital Transformation for enterprises and technology providers by delivering seamless customer experience, business efficiency and actionable insights through an integrated set of disruptive technologies: big data analytics, internet of things, mobility, cloud, security, unified communications, etc
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