Apache CouchDB: Difference between revisions

| screenshot = [[File:Couchdb screenshot.png|300px]]

| caption = CouchDB's Futon Administration Interface, User database

| author = Damien Katz, Jan Lehnardt, Noah Slater, Christopher Lenz, J. Chris Anderson, Paul Davis, Adam Kocoloski, Jason Davies, Benoît Chesneau, Filipe Manana, Robert Newson

| developer = [[Apache Software Foundation]]

}}

 

 

Unlike a [[relational database]], CouchDB does not store data and relationships in tables. Instead, each database is a collection of independent documents. Each document maintains its own data and self-contained schema. An application may access multiple databases, such as one stored on a user's mobile phone and another on a server. Document metadata contains revision information, making it possible to merge any differences that may have occurred while the databases were disconnected.

CouchDB implements a form of Multi-Version Concurrency Control ([[Multiversion concurrency control|MVCC]]) in order to avoid the need to lock the database file during writes. Conflicts are left to the application to resolve. Resolving a conflict generally involves first merging data into one of the documents, then deleting the stale one.<ref>{{cite web|last=Smith|first=Jason|title=What is the CouchDB replication protocol? Is it like Git?|url=http://stackoverflow.com/a/4766398/395287|work=StackOverflow|publisher=Stack Exchange|accessdate=14 April 2012}}</ref>

 

 

== History ==

 

In February 2008, it became an [[Apache Incubator]] project and the license was changed to the [[Apache License]].<ref>[http://mail-archives.apache.org/mod_mbox/incubator-general/200802.mbox/%3c3d4032300802121136p361b52ceyfc0f3b0ad81a1793@mail.gmail.com%3e Apache mailing list announcement] on mail-archives.apache.org</ref> A few months after, it graduated to a top-level project.<ref>[http://mail-archives.apache.org/mod_mbox/incubator-couchdb-dev/200811.mbox/%3c3F352A54-5FC8-4CB0-8A6B-7D3446F07462@jaguNET.com%3e Re: Proposed Resolution: Establish CouchDB TLP] on mail-archives.apache.org</ref> This led to the first stable version being released in July 2010.<ref>[http://www.pcworld.com/businesscenter/article/201046/couchdb_nosql_database_ready_for_production_use.html "CouchDB NoSQL Database Ready for Production Use"], article from PC World of Jully 2010</ref>

 

== Main features ==

; ACID Semantics

: CouchDB provides [[atomicity, consistency, isolation, durability|ACID]] semantics.<ref name="ACID">[http://couchdb.apache.org/docs/overview.html CouchDB, Technical Overview]</ref> It does this by implementing a form of [[Multi-Version Concurrency Control]], meaning that CouchDB can handle a high volume of concurrent readers and writers without conflict.

; Distributed Architecture with Replication

: CouchDB was designed with bi-direction replication (or synchronization) and off-line operation in mind. That means multiple replicas can have their own copies of the same data, modify it, and then sync those changes at a later time.

; Eventual Consistency

: CouchDB guarantees [[eventual consistency]] to be able to provide both availability and partition tolerance.

 

 

== Use cases & production deployments ==

 

CouchDB is well suited for applications with accumulating, occasionally changing data, on which pre-defined queries are to be run and where versioning is important (CRM, CMS systems, by example). Master-master replication is an especially interesting feature, allowing easy multi-site deployments.<ref name="Analyse Kristof Kovacs">[http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase comparison] from Kristóf Kovács</ref>

The following is a list of notable enterprises that have used or are using CouchDB:

* [[Amadeus IT Group]], for some of their back-end systems.{{cn|date=June 2015}}

* [[Sophos]], for some of their back-end systems.{{cn|date=June 2015}}

 

== Data manipulation: documents and views ==

Applications interact with CouchDB via HTTP. The following demonstrates a few examples using [[cURL]], a command-line utility. These examples assume that CouchDB is running on [[localhost]] (127.0.0.1) on port 5984.

 

|-

! Action !! Request !! Response

|-

| Accessing server information

|| <syntaxhighlight lang="javascript">{

"couchdb": "Welcome",

|-

| Creating a database named '''wiki'''

|| <syntaxhighlight lang="javascript">{"ok": true}</syntaxhighlight>

|-

| Attempting to create a second database named '''wiki'''

|| <syntaxhighlight lang="javascript" enclose="div">{

"error":"file_exists",

|-

|| Retrieve information about the '''wiki''' database

|| <syntaxhighlight lang="javascript">{

"db_name": "wiki",

|-

| Delete the database '''wiki'''

| <syntaxhighlight lang="javascript">{"ok": true}</syntaxhighlight>

|-

! License

|-

|-

| [[jQuery]]

| jQuery is a lightweight [[cross-browser]] [[JavaScript library]] that emphasizes interaction between [[JavaScript]] and [[HTML]].

| [[Dual license]]: [[GNU General Public License|GPL]] and [[MIT License|MIT]]

| [[MIT License]]

|-

| [[OpenSSL]]

| [[Apache License|Apache]]-like unique

|-

|}

 

==References==

 

==Bibliography==

* {{citation | first1 = Mick | last1 = Thompson | date = August 2, 2011 | title = Getting Started with GEO, CouchDB, and Node.js | edition = 1st | publisher = [[O'Reilly Media]] | pages = 64 | isbn = 1-4493-0752-3 | url = http://oreilly.com/catalog/9781449307523}}

{{Refend}}

 

==External links==

 

{{Apache}}

 

[[Category:Erlang (programming language)]]

[[Category:Free database management systems]]

[[Category:NoSQL]]

[[Category:Unix network-related software]]