PostgreSQL is a free software object-relational database management system (ORDBMS), released under a BSD-style license. It offers an alternative to other database systems. Similar to other free software projects such as Apache, GNU/Linux, and MediaWiki, PostgreSQL is not controlled by any single company, but relies on a global community of developers and companies to develop it. Image File history File links This is a lossless scalable vector image. ... Software development is the translation of a user need or marketing goal into a software product. ... A software release refers to the creation and availability of a new version of a computer software product. ... April 23 is the 113th day of the year in the Gregorian calendar (114th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ... A cross-platform (or platform independent) programming language, software application or hardware device works on more than one system platform (e. ... An OODBMS (object-oriented database management system) is a system offering DBMS facilities in an object-oriented programming environment. ... A software license is a legal agreement which may take the form of a proprietary or gratuitous license as well as a memorandum of contract between a producer and a user of computer software. ... The BSD license is a permissive license and is one of the most widely used free software licenses. ... A website (or Web site) is a collection of web pages, images, videos and other digital assets and hosted on a particular domain or subdomain on the World Wide Web. ... This article is about free software as defined by the sociopolitical free software movement; for information on software distributed without charge, see freeware. ... An object-relational database (ORD) or object-relational database management system (ORDBMS) is a relational database management system that allows developers to integrate the database with their own custom data types and methods. ... A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by Edgar F. Codd. ... The BSD license is a permissive license and is one of the most widely used free software licenses. ... It has been suggested that List of truly relational database management systems be merged into this article or section. ... The Apache HTTP Server is a web server for Unix-like systems, Microsoft Windows, Novell NetWare, Mac OS X and other operating systems. ... Unix systems filiation. ... MediaWiki is a wiki software package licensed under the GNU General Public License. ...

PostgreSQL's unusual-looking name makes some readers pause when trying to pronounce it, especially those who pronounce SQL as "sequel". PostgreSQL's developers pronounce it /poːst ɡɹɛs kjuː ɛl/. (Audio sample, 5.6k MP3). It is also common to hear it abbreviated as simply "postgres", which was its original name. The name refers to the project's origins as a "post-Ingres" database, the original authors having also developed the Ingres database. The related Category:SQL statements has been nominated for deletion, merging, or renaming. ... A portable MP3 player MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio encoding, lossy compression format, and algorithm, designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio... Ingres (pronounced ingress) is a commercially supported, open-source relational database management system. ...

Features

Functions

Functions allow blocks of code to be executed by the server. Although these blocks can be written in SQL, the lack of basic programming operations, such as branching and looping, has driven the adoption of other languages inside of functions. Some of the languages can even execute inside of triggers. Functions in PostgreSQL can be written in the following languages: The word iteration is sometimes used in everyday English with a meaning virtually identical to repetition. ...

• A built-in language called PL/pgSQL resembles Oracle's procedural language PL/SQL.
• Scripting languages are supported through PL/Perl, plPHP, PL/Python, PL/Ruby, PL/sh, PL/Tcl and PL/Scheme.
• Compiled languages C, C++, or Java (via PL/Java).
• The statistical language R through PL/R.

PostgreSQL supports row-returning functions, where the output of the function is a set of values which can be treated much like a table within queries. PL/pgSQL (Procedural Language/PostgreSQL Structured Query Language) is a procedural language built into the PostgreSQL RDBMS. It closely resembles Oracles PL/SQL language. ... PL/SQL (Procedural Language/Structured Query Language) is Oracle Corporations proprietary server-based procedural extension to the SQL database language. ... PL/Perl (Procedural Language/Perl) is a procedural language supported by the PostgreSQL RDBMS. PL/Perl, as a true programming language, allows much more control than basic SQL, including the ability to use loops, advanced control structures, and quite sophisticated text manipulation. ... C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ... C++ (pronounced see plus plus, IPA: ) is a general-purpose, high-level programming language with low-level facilities. ... The R programming language, sometimes described as GNU S, is a programming language and software environment for statistical computing and graphics. ...

Functions can be defined to execute with the privileges of either the caller or the user who defined the function. Functions are sometimes referred to as stored procedures, although there is a slight technical distinction between the two. A stored procedure is a program (or procedure) which is physically stored within a database. ...

Indices

User-defined index methods can be created, or the built-in B-tree, hash table and GiST indices can be used. Indexes in PostgreSQL also support the following features: It has been suggested that Bitmap index be merged into this article or section. ... B-trees are tree data structures that are most commonly found in databases and filesystem implementations. ... In computer science, a hash table is a data structure that speeds up searching for information by a particular aspect of that information, called a key. ... In computing, GiST or Generalized Search Tree, is a data structure and API which can be used to build almost any kind of search tree on almost any kind of data. ...

• PostgreSQL is capable of scanning indexes backwards when needed; you never need a separate index to support ORDER BY field DESC.
• Expression indexes can be created with an index of the result of an expression or function, instead of simply the value of a column.
• Partial indexes, which only index part of a table, can be created by adding a WHERE clause to the end of the CREATE INDEX statement. This allows a smaller index to be created.
• Bitmap index scans are supported as of version 8.1. This involves reading multiple indexes and generating a bitmap that expresses their intersection with the tuples that match the selection criteria. This provides a way of composing indexes together; on a table with 20 columns, there are, in principle, 20! indexes that could be defined - which is far too many to actually use. If you create one index on each column, bitmap scans can compose arbitrary combinations of those indexes at query time for each column that seems worth considering as a constraint.

The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... A partial index is a database index which has some condition applied to it such that it only includes a portion of the rows in the table. ... A bitmapped index is a special kind of index that is particularly useful in data warehousing for columns that have a low number of distinct values (low cardinality). ... In mathematics, the intersection of two sets A and B is the set that contains all elements of A that also belong to B (or equivalently, all elements of B that also belong to A), but no other elements. ... In mathematics, a tuple is a finite sequence (also known as an ordered list) of objects, each of a specified type. ... For factorial rings in mathematics, see unique factorisation domain. ...

Triggers

Triggers are events triggered by the action of SQL query. For example, an INSERT query might activate a trigger that checked if the values of the query were valid. Most triggers are only activated by either INSERT or UPDATE queries.

Triggers are fully supported and can be attached to tables but not to views. Views can have rules, though. Multiple triggers are fired in alphabetical order. In addition to calling functions written in the native PL/PgSQL, triggers can also invoke functions written in other languages like PL/Perl. A database trigger is procedural code that is automatically executed in response to certain events on a particular table in a database. ...

MVCC

PostgreSQL manages concurrency through a system known as Multi-Version Concurrency Control (MVCC), which gives each user a "snapshot" of the database, allowing changes to be made without being visible to other users until a transaction is committed. This largely eliminates the need for read locks, and ensures the database maintains the ACID principles in an efficient manner. In computer science -- more specifically, in the field of databases -- concurrency control is a method used to ensure that database transactions are executed in a safe manner (i. ... In computer science, in the field of databases, multiversion concurrency control (abbreviated MCC or MVCC) is a concurrency control method commonly used by database management systems to provide concurrent access to the database. ... Acidity redirects here. ...

Rules

Rules allow the "query tree" of an incoming query to be rewritten. One common usage is to implement updatable views.

Data types

A wide variety of native data types are supported, including: In computer science, a datatype or data type (often simply a type) is a name or label for a set of values and some operations which one can perform on that set of values. ...

• Arbitrary precision numerics
• Unlimited length text
• Geometric primitives
• IP and IPv6 addresses
• CIDR blocks, and MAC address data types
• Arrays

In addition, users can create their own data types which can usually be made fully indexable via PostgreSQL's GiST infrastructure. Arbitrary precision mathematical libraries allow computer programs to perform calculations and then specify how many digits will be used for the result. ... An IP address is a unique number, akin to a telephone number, used by machines (usually computers) to refer to each other when sending information through the Internet using the Internet Protocol. ... Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. ... It has been suggested that this article or section be merged with Provider-based addressing. ... In computer networking a Media Access Control address (MAC address) is a unique identifier attached to most network adapters (NICs). ... In computing, GiST or Generalized Search Tree, is a data structure and API which can be used to build almost any kind of search tree on almost any kind of data. ...

Examples of these are the Geographic information system (GIS) data types from the PostGIS project for PostgreSQL. A geographic information system (GIS) is a system for capturing, storing, analyzing and managing data and associated attributes which are spatially referenced to the earth. ... PostGIS is a geographic information system software program that adds support for geographic objects to the PostgreSQL object-relational database. ...

User-defined objects

New types of almost all objects inside the database can be created, including:

• Indices
• Operators (existing ones can be overloaded)
• Aggregate functions
• Domains
• Casts
• Conversions

In computer programming, operator overloading (less commonly known as operator ad-hoc polymorphism) is a specific case of polymorphism in which some or all of operators like +, = or == have different implementations depending on the types of their arguments. ... In computer science, an aggregate function is a function that compute a single result value from a collection of input values such as a set, a bag or a list. ... In data management and database analysis, a data domain refers to all the unique values within a column. ...

Inheritance

Tables can be set to inherit their characteristics from a "parent" table. Data is shared between "parent" and "child(ren)" tables. Tuples inserted or deleted in the "child" table will respectively be inserted or deleted in the "parent" table. Also adding a column in the parent table will cause that column to appear in the child table as well. This feature is not fully supported yet -- in particular, table constraints are not currently inheritable. This means that attempting to insert the id of a row from a child table into table that has a foreign key constraint referencing a parent table will fail because Postgres doesn't recognize that the id from the child table is also a valid id in the parent table.

Inheritance provides a way to map the features of generalization hierarchies depicted in Entity Relationship Diagrams (ERD) directly into the PostgreSQL database.

Other features

• Referential integrity constraints including foreign key constraints, column constraints, and row checks
• Views While updateable views have not been implemented, the same functionality can be achieved using the rules system.
• Full, inner, and outer (left and right) joins
• Sub-selects
• Transactions
• Supports most of the major features of SQL:2003 standard [1] unsupported supported <-- lead to documentation for the next release of PostgreSQL, follow this link to find manuals for already released versions of PostgreSQL
• Encrypted connections via SSL
• Binary and textual large-object storage
• Online backup
• Domains
• Tablespaces
• Savepoints
• Point-in-time recovery
• Two-phase commit
• TOAST (The Oversized-Attribute Storage Technique) is used to transparently store large table attributes (such as big MIME attachments or XML messages) in a separate area, with automatic compression.
• Regular expressions [2]

An example of a database that has not enforced referential integrity. ... A constraint is a limitation of possibilities. ... In the context of a relational database, a foreign key (FK) is a field or group of fields in a database record that points to a key field or group of fields forming a key of another database record in some (usually different) table. ... In database theory, a view is a virtual or logical table composed of the result set of a query. ... A join combines records from two tables in a relational database and results in a new (temporary) table, also called joined table. ... A SELECT statement in SQL returns a result set of records from one or more tables. ... A database transaction is a unit of interaction with a database management system or similar system that is treated in a coherent and reliable way independent of other transactions that must be either entirely completed or aborted. ... Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide secure communications on the Internet. ... In data management and database analysis, a data domain refers to all the unique values within a column. ... A tablespace is a location in the file system where the files representing database objects can be stored. ... A savepoint is a way of implementing subtransactions (also known as nested transactions) within a relational database management system by indicating a point within a transaction that can be rolled back to without affecting any work done in the transaction before the savepoint was created. ... Point-in-time recovery in the context of computers is a system whereby a set of data or a particular setting can be restored or recovered from a time in the past. ... It has been suggested that this article or section be merged into Two-phase-commit protocol. ... In computing, a regular expression is a string that is used to describe or match a set of strings, according to certain syntax rules. ...

Add-ons

• Geographic objects via PostGIS. GPL.
• Full text search via Tsearch2 and OpenFTS. GPL.
• Several asynchronous master/slave replication packages, including Slony-I (BSD license) and Mammoth Replicator.
• XML/XSLT support via XPath Extensions in the contrib section. GPL.

PostGIS is a geographic information system software program that adds support for geographic objects to the PostgreSQL object-relational database. ... In text retrieval, full text search (also called free search text) refers to a technique for searching a computer-stored document or database; in a full text search, the search engine examines all of the words in every stored document as it tries to match search words supplied by the... OpenFTS is an open source database search engine based on PostgreSQL. It is distributed under the GNU General Public License. ...

History

PostgreSQL has had a lengthy evolution, starting with the Ingres project at UC Berkeley. The project leader, Michael Stonebraker, had left Berkeley to commercialize Ingres in 1982, but eventually returned to academia. After returning to Berkeley in 1985, Stonebraker started a post-Ingres project to address the problems with contemporary database systems that had become increasingly clear during the early 1980s. While they share many of the same ideas, the code bases of PostgreSQL and Ingres started (and remain) completely separated. Ingres (pronounced ingress) is a commercially supported, open-source relational database management system. ... The University of California, Berkeley (also known as Cal, UC Berkeley, UCB, or simply Berkeley) is a prestigious, public, coeducational university situated in the foothills of Berkeley, California to the east of San Francisco Bay, overlooking the Golden Gate and its bridge. ... Michael Stonebraker is a computer scientist specializing in database research and development. ...

The resulting project, named POSTGRES, aimed to introduce the minimum number of features needed to add complete support for types. These features included the ability to define types, but also the ability to fully describe relationships – something used widely before this time but maintained entirely by the user. In POSTGRES the database "understood" relationships, and could retrieve information in related tables in a natural way using rules.

Starting in 1986 the team released a number of papers describing the basis of the system, and by 1988 the project had a prototype version up and running. The team released version 1 to a small number of users in June 1989, followed by version 2 with a re-written rules system in June 1990. 1991's version 3 re-wrote the rules system again, but also added support for multiple storage managers and for an improved query engine. By 1993 a huge number of users existed and began to overwhelm the project with requests for support and features. After releasing a Version 4 — primarily as a cleanup — the project ended.

Although the POSTGRES project had officially ended, the BSD license (under which Berkeley had released POSTGRES) enabled open-source developers to obtain copies and to develop the system further. In 1994 two UC Berkeley graduate students, Andrew Yu and Jolly Chen, added a SQL language interpreter to replace the earlier Ingres-based QUEL system, creating Postgres95. The code was subsequently released to the web to find its own way in the world. The BSD license is a permissive license and is one of the most widely used free software licenses. ... Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ... Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... The related Category:SQL statements has been nominated for deletion, merging, or renaming. ... QUEL is a relational database access language, similar in most ways to SQL, but somewhat better arranged and easier to use. ...

In July 1996, Marc Fournier at Hub.Org Networking Services provided the first non-university development server for the open source development effort. Along with Bruce Momjian and Vadim B. Mikheev, work began to stabilize the code inherited from UC Berkeley, with the first open source version released on August 1st 1996.

1996 saw a re-naming of the project: in order to reflect the database's new SQL query language, Postgres95 became PostgreSQL. The first PostgreSQL release formed version 6.0 in January 1997. Since then, a group of database developers and volunteers from around the world, coordinating via the Internet, have maintained the software.

Although the license allowed for the commercialization of Postgres, the Postgres code did not develop commercially with the same rapidity as Ingres — somewhat surprisingly considering the advantages Postgres offered. The main offshoot originated when Paula Hawthorn (an original Ingres team member who moved from Ingres) and Michael Stonebraker formed Illustra Information Technologies to commercialize Postgres.

In 2000, former Red Hat investors put together a company known as Great Bridge to commercialize PostgreSQL and compete against commercial database vendors. Great Bridge sponsored several PostgreSQL developers and donated many resources back to the community, however by late 2001 the company closed its doors citing tough competition from companies like Red Hat as well as poor market conditions.

In 2001, Command Prompt, Inc. released Mammoth PostgreSQL, the oldest surviving commercial PostgreSQL distribution. They continue to actively support the PostgreSQL community through developer sponsorships and projects including PL/Perl, PL/php, and hosting of community projects such as the PostgreSQL Build Farm.

In January 2005, PostgreSQL received backing by another database vendor. Pervasive Software, well known for their Btrieve product which was ubiquitous on the Novell NetWare platform, announced commercial support & community participation. While they achieved success for a time, in July 2006, Pervasive left the PostgreSQL support market.^[1] Pervasive Software is a maker of data infrastructure software. ... In computing, Btrieve is a navigational database based on Indexed Sequential Access Method (ISAM), a way of storing data for fast retrieval. ... NetWare is a network operating system developed by Novell, Inc. ...

In mid-2005 two other companies announced plans to commercialize PostgreSQL with focus on separate niche markets. EnterpriseDB announced plans to focus on adding functionality to allow applications written to work with Oracle to be more readily run atop PostgreSQL. Greenplum contributed enhancements directed at data warehouse and business intelligence applications, notably including the BizGres project. This article is being considered for deletion in accordance with Wikipedias deletion policy. ... An Oracle database consists of a collection of data managed by an Oracle database management system. ... Founded in June 2003, Greenplum is headquartered in San Mateo, California and has offices in the United States, Europe, and Asia. ... This article or section does not cite its references or sources. ... This article or section does not adequately cite its references or sources. ...

In October 2005, John Loiacono, executive vice-president of software at Sun Microsystems, commented that "We're not going to OEM Microsoft but we are looking at PostgreSQL right now,"^[2] although no specifics were released at that time. By November 2005, Sun Microsystems had announced support for PostgreSQL.^[3] As of June 2006, Sun Solaris 10 6/06 ships PostgreSQL. Sun Microsystems, Inc. ... Original equipment manufacturer, or OEM, is a term that refers to a situation in which one company purchases a manufactured product from another company and resells the product as its own, usually as a part of a larger product the original company is selling. ...

As for the PostgreSQL project itself, it continues to make yearly major releases and minor "bugfix" releases, all available under the BSD license, based on contributions from both commercial vendors, support companies, and open source hackers at large.

Prominent users

• .org domain registry [3]
• The American Chemical Society
• Chicagocrime.org (Adrian Holovaty's blog)
• Skype (PostgreSQL Users)
• Penny Arcade (PostgreSQL Users)
• IMDB (PostgreSQL Users)
• Sony Online (ComputerWorld Article) (March 20, 2006)
• U.S. Department of Labor (PostgreSQL Users)
• whitepages.com
• Wisconsin Circuit Court Access with 6 * 180GB DBs replicated in real time
• OpenACS and dotLRN

.org (organization) is a generic top-level domain (gTLD) used in the Internets Domain Name System. ... The American Chemical Society (ACS) is a learned society (professional association) based in the United States that supports scientific inquiry in the field of chemistry. ... Skype (IPA pronunciation: , rhymes with type) is a peer-to-peer Internet telephony network founded by the entrepreneurs Niklas Zennström and Janus Friis, also founders of the file sharing application Kazaa. ... ... The Internet Movie Database (IMDb) [1] is an online database of information about actors, movies, television shows, television stars and video games. ... Sony Online Entertainment (SOE) is a computer game development division of Sony that mostly creates massively multiplayer online games. ...

See also

• List of relational database management systems
• Comparison of relational database management systems
• Comparison of object-relational database management systems

Image File history File links Portal. ... It has been suggested that List of truly relational database management systems be merged into this article or section. ... The following tables compare general and technical information for a number of relational database management systems. ... This article or section is not written in the formal tone expected of an encyclopedia article. ...

References

• Matthew, Neil; Stones, Richard. Beginning Databases with PostgreSQL, Second Edition. ISBN 1-59059-478-9. 
• Gilmore, W. Jason; Treat, Robert. Beginning PHP and PostgreSQL 8: From Novice to Professional. ISBN 1-59059-547-5. 
• Worsley, John C.; Drake, Joshua D.. Practical PostgreSQL. ISBN 1-56592-846-6. 
• Douglas, Korry. PostgreSQL. ISBN 0-672-32756-2. 

Notes

This article is being considered for deletion in accordance with Wikipedias deletion policy. ... Pervasive Software is a maker of data infrastructure software. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... February 13 is the 44th day of the year in the Gregorian calendar. ... Computerworld is an IT magazine that provides information to technology managers. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... February 13 is the 44th day of the year in the Gregorian calendar. ... Sun Microsystems, Inc. ... A news release, press release or press statement is a written or recorded communication directed at members of the news media for the purpose of announcing something claimed as having news value. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the Anno Domini (common) era. ... February 13 is the 44th day of the year in the Gregorian calendar. ...

External links

• PostgreSQL FAQ (Frequently Asked Questions)
• PostgreSQL Website
• PostgreSQL Documentation
• PostgreSQL Universe Comprehensive (Link-)Directory
• PostgreSQL at the Open Directory Project
• Planet PostgreSQL, blog aggregator
• PostgreSQL Performance Tuning
• Tuning PostgreSQL for performance
• Annotated POSTGRESQL.CONF Guide for PostgreSQL
• SourceForge PostgreSQL-related projects
• PgFoundry PostgreSQL-related projects
• Open Source Database Network
• Database Journal articles on PostgreSQL
• A PostgreSQL Tutorial
• Linux Productivity Magazine: a complete issue on PostgreSQL
• a rebuttal to the FUD (fear, uncertainty, and doubt) surrounding much of the criticism against PostgreSQL.
• PostgreSQL gotchas, documented but counterintuitive behavior
• Test_PGC, Example embedded SQL/C program for PostgreSQL showing database operations and SQLSTATE testing.