![]() ![]() Step 2 − Initialize the QueryParser object created with a standard analyzer having version information and index name on which this query is to be run. Follow these steps to create a QueryParser − Apache Lucene is a high-performance, full-featured text search engine library written in Java. QueryParser class parses the user entered input into Lucene understandable format query. ![]() We will now show you a step-wise approach and help you understand the indexing process using a basic example. IndexSearcher returns a TopDocs object which contains the search details along with document ID(s) of the Document which is the result of the search operation. Then we create a Query with a Term and make a search using IndexSearcher by passing the Query to the searcher. We first create Directory(s) containing indexes and then pass it to IndexSearcher which opens the Directory using IndexReader. IndexSearcher is one of the core components of the searching process. Following diagram illustrates the process and its use. The Lucene query language allows the user to specify which field(s) to search on, which fields to give more weight to (boosting), the ability to perform boolean queries (AND, OR, NOT) and other functionality.The process of searching is one of the core functionalities provided by Lucene. Lucene has its own mini-language for performing searches. It involves creating a Query (usually via a QueryParser) and handing this Query to an IndexSearcher, which returns a list of Hits. Searching requires an index to have already been built. Indexing in Lucene thus involves creating Documents comprising of one or more Fields, and adding these Documents to an IndexWriter. In the case of a title Field, the field name is title and the value is the title of that content item. For example, a Field commonly found in applications is title. For example, if you're creating a Lucene index of a database table of users, then each user would be represented in the index as a Lucene Document.Ī Document consists of one or more Fields. Indexing involves adding Documents to an IndexWriter, and searching involves retrieving Documents from an index via an IndexSearcher.Ī Lucene Document doesn't necessarily have to be a document in the common English usage of the word. In Lucene, a Document is the unit of search and index.Īn index consists of one or more Documents. This type of index is called an inverted index, because it inverts a page-centric data structure (page->words) to a keyword-centric data structure (word->pages). This would be the equivalent of retrieving pages in a book related to a keyword by searching the index at the back of a book, as opposed to searching the words in each page of the book. Lucene is able to achieve fast search responses because, instead of searching the text directly, it searches an index instead. The content you add to Lucene can be from various sources, like a SQL/NoSQL database, a filesystem, or even from websites. It then allows you to perform queries on this index, returning results ranked by either the relevance to the query or sorted by an arbitrary field such as a document's last modified date. It does so by adding content to a full-text index. Lucene is a full-text search library in Java which makes it easy to add search functionality to an application or website. ![]()
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