How to Create a Search Engine using Apache Lucene

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What is Lucene?

  • Lucene is a powerful and flexible search engine library that can be used to build a variety of search applications
  • It provides a high-performance indexing and search engine, as well as a wide range of features such as spell checking, hit highlighting, and advanced analysis/tokenization capabilities.
  • Lucene is used by a wide range of applications, including:
    • Web search engines
    • Document management systems
    • Enterprise search applications
    • Personal information managers
    • E-commerce websites
    • Content management systems

How Does Search Engine Work?

If you don't already know, Google does not search the internet!!

Wait, Whaaat?

Yes, Google DOES NOT search the internet, instead it searches the index which is created from the content of the internet.

In simple words, Google takes the content from the internet (Product websites, Blogs, News Articles etc) and creates a "Index" and when the search query is hit, Google searches this index and returns you the results.

Lucene works in similar fashion, it helps you create the index from the content and then you can perform text search on it.



Components of Lucene

    • Directory: A directory is a storage location for Lucene indexes. Indexes are made up of a set of files that store the data that is being indexed.
    • Document: A document is a unit of data that is being indexed. Documents can contain any type of data, such as text, images, or audio.
    • Analyzer: An analyzer is used to tokenize documents. Tokenization is the process of breaking down documents into smaller units of text, such as words or phrases.
    • IndexWriter: An index writer is used to create and update indexes. Index writers add documents to indexes and update the indexes when documents are changed or deleted.
    • IndexReader: An index reader is used to read indexes. Index readers allow applications to search and retrieve data from indexes.
    • QueryParser: A query parser is used to parse queries. Query parsers convert queries into a format that can be used to search indexes.
    • Searcher: A searcher is used to search indexes. Searchers allow applications to search for documents that match a query.

    Types of Directory

    Index is stored inside a directory and there are several options for the same:
    • FSDirectory: This is the most common type of directory supported by Lucene. It stores index files on the filesystem.
    • NIODirectory: This type of directory uses the Java NIO API to access index files. This makes it ideal for applications that need to access index files on a variety of filesystems.
    • SimpleFSDirectory: This type of directory is a simplified version of FSDirectory. It is useful for applications that do not need all of the features of FSDirectory.
    • RAMDirectory: This type of directory stores index files in memory. This makes it ideal for applications that need to access index files quickly.
    • MMapDirectory: This type of directory stores index files in memory-mapped files. This makes it ideal for applications that need to access index files very quickly.

    Demo Example Source Code: https://github.com/vinz/lucene

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