Apache Solr

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Solr logo
Developer(s) Apache Software Foundation
Stable release
6.6.0 / June 6, 2017; 31 days ago (2017-06-06)
Repository git.apache.org/lucene-solr.git
Development status Active
Written in Java
Operating system Cross-platform
Type Search and index API
License Apache License 2.0
Website lucene.apache.org/solr/

Solr (pronounced "solar") is an open source enterprise search platform, written in Java, from the Apache Lucene project. Its major features include full-text search, hit highlighting, faceted search, real-time indexing, dynamic clustering, database integration, NoSQL features[1] and rich document (e.g., Word, PDF) handling. Providing distributed search and index replication, Solr is designed for scalability and fault tolerance.[2] Solr is the second-most popular enterprise search engine after Elasticsearch.[3]

Solr runs as a standalone full-text search server. It uses the Lucene Java search library at its core for full-text indexing and search, and has REST-like HTTP/XML and JSON APIs that make it usable from most popular programming languages. Solr's external configuration allows it to be tailored to many types of application without Java coding, and it has a plugin architecture to support more advanced customization.

Apache Lucene and Apache Solr are both produced by the same Apache Software Foundation development team since the two projects were merged in 2010. It is common to refer to the technology or products as Lucene/Solr or Solr/Lucene.


In 2004, Solr was created by Yonik Seeley at CNET Networks as an in-house project to add search capability for the company website.

In January 2006, CNET Networks decided to openly publish the source code by donating it to the Apache Software Foundation.[4] Like any new Apache project, it entered an incubation period which helped solve organizational, legal, and financial issues.

In January 2007, Solr graduated from incubation status into a standalone top-level project (TLP) and grew steadily with accumulated features, thereby attracting users, contributors, and committers. Although quite new as a public project, it powered several high-traffic websites.[5]

In September 2008, Solr 1.3 was released including distributed search capabilities and performance enhancements among many others.[6]

In January 2009, solr and enterprise search Yonik Seeley along with Grant Ingersoll and Erik Hatcher joined Lucidworks (formerly Lucid Imagination), the first company providing commercial support and training for Apache Solr search technologies[citation needed]. Since then, support offerings around Solr has been abundant.[7]

November 2009 saw the release of Solr 1.4. This version introduced enhancements in indexing, searching and faceting along with many other improvements such as rich document processing (PDF, Word, HTML), Search Results clustering based on Carrot2 and also improved database integration. The release also features many additional plug-ins.[8]

In March 2010, the Lucene and Solr projects merged.[9] Solr became a Lucene sub project. Separate downloads continued, but the products were now jointly developed by a single set of committers.

In 2011 the Solr version number scheme was changed in order to match that of Lucene. After Solr 1.4, the next release of Solr was labeled 3.1, in order to keep Solr and Lucene on the same version number.[10]

In October 2012 Solr version 4.0 was released, including the new SolrCloud feature.[11] 2013 and 2014 saw a number of Solr releases in the 4.x line, steadily growing the feature set and improving reliability.

In February 2015, Solr 5.0 was released,[12] the first release where Solr is packaged as a standalone application,[13] ending official support for deploying Solr as a war. Solr 5.3 featured a built-in pluggable Authentication and Authorization framework.[14]

In April 2016, Solr 6.0 was released.[15] Added support for executing Parallel SQL queries across SolrCloud collections. Includes StreamExpression support and a new JDBC Driver for the SQL Interface.



  • Uses the Lucene library for full-text search
  • Faceted navigation
  • Hit highlighting
  • Query language supports structured as well as textual search
  • Schema-less mode and Schema REST API
  • JSON, XML, PHP, Ruby, Python, XSLT, Velocity and custom Java binary output formats over HTTP
  • HTML administration interface
  • Built-in security: Authentication, Authorization, SSL
  • Replication to other Solr servers - enables scaling QPS and High availability
  • Distributed Search through Sharding - enables scaling content volume
  • Search results clustering based on Carrot2
  • Extensible through plugins
  • Flexible relevance - boost through function queries
  • Caching - queries, filters, and documents
  • Embeddable in a Java Application
  • Geo-spatial search, including multiple points per documents and polygons
  • Automated management of large clusters through ZooKeeper
  • Function queries
  • Field Collapsing and grouping[16]
  • Auto-suggest
  • Streaming


Solr has both individuals and companies who contribute new features and bug fixes.[17] [18] [19] [20] [21]

Integrating Solr[edit]

Solr is bundled as the built-in search in many applications such as content management systems and enterprise content management systems. Hadoop distributions from Cloudera,[22] Hortonworks[23] and MapR all bundle Solr as the search engine for their products marketed for big data. DataStax DSE integrates Solr as a search engine with Cassandra.[24] Solr is supported as an end point in various data processing frameworks and Enterprise integration frameworks.[citation needed]

Solr exposes industry standard HTTP REST-like APIs with both XML and JSON support, and will integrate with any system or programming language supporting these standards. For ease of use there are also client libraries available for Java, C#, PHP, Python, Ruby and most other popular programming languages.[25]

Managed Services[edit]

Some organizations offer Solr as a managed service, including SearchStax by Measured Search.[26] Such managed services provide hosting, deployment, backup and other support as a package, reducing the resources, skills and time needed to implement and operate Solr.

See also[edit]


  1. ^ "Archived copy". Archived from the original on 2014-07-06. Retrieved 2014-07-10. 
  2. ^ "Apache Solr -". apache.org. Retrieved 16 January 2017. 
  3. ^ "DB-Engines Ranking - popularity ranking of search engines". db-engines.com. Retrieved 16 January 2017. 
  4. ^ "[SOLR-1] CNET code contribution - ASF JIRA". apache.org. Retrieved 16 January 2017. 
  5. ^ "PublicServers - Solr Wiki". apache.org. Retrieved 16 January 2017. 
  6. ^ "Apache Solr -". apache.org. Retrieved 16 January 2017. 
  7. ^ "Support - Solr Wiki". apache.org. Retrieved 16 January 2017. 
  8. ^ "Apache Solr -". apache.org. Retrieved 16 January 2017. 
  9. ^ "[VOTE] merge lucene/solr development (take 3) - Yonik Seeley - org.apache.lucene.general - MarkMail". markmail.org. Retrieved 16 January 2017. 
  10. ^ Solr3.1 - Solr Wiki. Wiki.apache.org (2013-05-16). Retrieved on 2013-07-21.
  11. ^ Apache Lucene. Lucene.apache.org. Retrieved on 2013-07-21.
  12. ^ "Apache Solr - News". apache.org. Retrieved 16 January 2017. 
  13. ^ "[SOLR-6733] Umbrella issue - Solr as a standalone application - ASF JIRA". apache.org. Retrieved 16 January 2017. 
  14. ^ "Solr 5.3 Release announcement". lucene.apache.org. Retrieved 2015-09-24. 
  15. ^ "Apache Solr - News". apache.org. Retrieved 16 January 2017. 
  16. ^ Solr Result Grouping
  17. ^ "Highest Voted 'solr' Questions". stackoverflow.com. Retrieved 16 January 2017. 
  18. ^ "Lucene/Solr Revolution 2016". lucenerevolution.org. Retrieved 16 January 2017. 
  19. ^ "SFBay Apache Lucene/Solr Meetup". meetup.com. Retrieved 16 January 2017. 
  20. ^ "Oslo Solr Community". meetup.com. Retrieved 16 January 2017. 
  21. ^ "LinkedIn Solr Group". linkedin.com. Retrieved 16 January 2017. 
  22. ^ "Hadoop for Everyone: Inside Cloudera Search - Cloudera Engineering Blog". cloudera.com. 24 June 2013. Retrieved 16 January 2017. 
  23. ^ "Bringing Enterprise Search to Enterprise Hadoop - Hortonworks". hortonworks.com. 2 April 2014. Retrieved 16 January 2017. 
  24. ^ "DataStax Enterprise: Cassandra with Solr Integration Details". datastax.com. 12 April 2012. Retrieved 6 February 2017. 
  25. ^ "IntegratingSolr - Solr Wiki". apache.org. Retrieved 16 January 2017. 
  26. ^ "Hosted Solr Service | AWS Microsoft Azure Google Cloud | Measured Search". www.measuredsearch.com. Retrieved 2017-05-26. 


External links[edit]