asfenaudio.blogg.se - Training apache lucene

#TRAINING APACHE LUCENE UPDATE#
#TRAINING APACHE LUCENE SOFTWARE#
#TRAINING APACHE LUCENE SERIES#

This is called an inverted index because it reverses the usual mapping of a document to the terms it contains. The Lucene index provides a mapping from terms to documents.

The terms created from text fields are pairs of field name and token. The terms created from the non-text fields in the document are pairs consisting of the field name and the field value. A term combines a field name with a token. Lucene indexes terms, which means that Lucene search searches over terms. An index may store a heterogeneous set of documents, with any number of different fields that may vary by a document in arbitrary ways. Lucene manages an index over a dynamic collection of documents and provides very rapid updates to the index as documents are added to and deleted from the collection. In this section, we will see how does Apache Lucene work towards documents indexing and searching. Implementations in other programming languages are available that are index-compatible.

#TRAINING APACHE LUCENE SOFTWARE#

Available as Open Source software under the Apache License which lets you use Lucene in both commercial and Open Source programs.

Provides configurable storage engine (codecs).

Provides pluggable ranking models, including the Vector Space Model and Okapi BM25.

It is fast, memory-efficient and typo-tolerant suggesters.

Has flexible faceting, highlighting, joins and result grouping.

#TRAINING APACHE LUCENE UPDATE#

It allows simultaneous update and searching.

Supports multiple-index searching with merged results.

Supports many powerful query types: phrase queries, wildcard queries, proximity queries, range queries and more.

Powerful, Accurate, and Efficient Search Algorithms

Index size roughly 20-30% the size of text indexed.

Incremental indexing as fast as batch indexing.

Small RAM requirements - only 1MB heap.

In a nutshell, the features of Lucene can be described as follows: Scalable and High-Performance Indexing As of now, Lucene 6, the Lucene distribution contains approximately two dozen package-specific jars, these cuts down on the size of an application at a small cost to the complexity of the build file. The Lucene API consists of a core library and many contributed libraries. Lucene has a highly expressive search API that takes a search query and returns a set of documents ranked by relevancy with documents most similar to the query having the highest score. Lucene provides many ways to break a piece of text into tokens as well as hooks that allow you to write custom tokenizers.

#TRAINING APACHE LUCENE SERIES#

There are two ways to store text data: string fields store the entire item as one string text fields store the data as a series of tokens.

Fields are constrained to store only one kind of data, either binary, numeric, or text data. Lucene does not in any way constrain document structures. A field consists of a field name that is a string and one or more field values. Lucene provides search over documents where a document is essentially a collection of fields. Therefore, it’s popular in both academic and commercial settings due to its performance, reconfigurability, and generous licensing terms. Most importantly, it is a cross-platform solution. It utilizes powerful, accurate and efficient search algorithms written in Java. Lucene offers powerful features like scalable and high-performance indexing of the documents and search capability through a simple API. A step-by-step example of documents indexing and searching will be shown too. In this article, we will see some exciting features of Apache Lucene. It is a technology suitable for nearly any application that requires full-text search, especially in a cross-platform environment. Apache Lucene is a high-performance and full-featured text search engine library written entirely in Java from the Apache Software Foundation.