2. A Brief History ofPostgreSQL#
The object-relational database management system now known asPostgreSQL is derived from thePOSTGRES package written at the University of California at Berkeley. With decades of development behind it,PostgreSQL is now the most advanced open-source database available anywhere.
2.1. The BerkeleyPOSTGRES Project#
ThePOSTGRES project, led by Professor Michael Stonebraker, was sponsored by the Defense Advanced Research Projects Agency (DARPA), the Army Research Office (ARO), the National Science Foundation (NSF), and ESL, Inc. The implementation ofPOSTGRES began in 1986. The initial concepts for the system were presented in[ston86], and the definition of the initial data model appeared in[rowe87]. The design of the rule system at that time was described in[ston87a]. The rationale and architecture of the storage manager were detailed in[ston87b].
POSTGRES has undergone several major releases since then. The first“demoware” system became operational in 1987 and was shown at the 1988ACM-SIGMOD Conference. Version 1, described in[ston90a], was released to a few external users in June 1989. In response to a critique of the first rule system ([ston89]), the rule system was redesigned ([ston90b]), and Version 2 was released in June 1990 with the new rule system. Version 3 appeared in 1991 and added support for multiple storage managers, an improved query executor, and a rewritten rule system. For the most part, subsequent releases untilPostgres95 (see below) focused on portability and reliability.
POSTGRES has been used to implement many different research and production applications. These include: a financial data analysis system, a jet engine performance monitoring package, an asteroid tracking database, a medical information database, and several geographic information systems.POSTGRES has also been used as an educational tool at several universities. Finally, Illustra Information Technologies (later merged intoInformix, which is now owned byIBM) picked up the code and commercialized it. In late 1992,POSTGRES became the primary data manager for the Sequoia 2000 scientific computing project described in[ston92].
The size of the external user community nearly doubled during 1993. It became increasingly obvious that maintenance of the prototype code and support was taking up large amounts of time that should have been devoted to database research. In an effort to reduce this support burden, the BerkeleyPOSTGRES project officially ended with Version 4.2.
2.2. Postgres95#
In 1994, Andrew Yu and Jolly Chen added an SQL language interpreter toPOSTGRES. Under a new name,Postgres95 was subsequently released to the web to find its own way in the world as an open-source descendant of the originalPOSTGRES Berkeley code.
Postgres95 code was completely ANSI C and trimmed in size by 25%. Many internal changes improved performance and maintainability.Postgres95 release 1.0.x ran about 30–50% faster on the Wisconsin Benchmark compared toPOSTGRES, Version 4.2. Apart from bug fixes, the following were the major enhancements:
The query language PostQUEL was replaced withSQL (implemented in the server). (Interface librarylibpq was named after PostQUEL.) Subqueries were not supported untilPostgreSQL (see below), but they could be imitated inPostgres95 with user-definedSQL functions. Aggregate functions were re-implemented. Support for the
GROUP BYquery clause was also added.A new program (psql) was provided for interactive SQL queries, which usedGNUReadline. This largely superseded the oldmonitor program.
A new front-end library,
libpgtcl, supportedTcl-based clients. A sample shell,pgtclsh, provided new Tcl commands to interfaceTcl programs with thePostgres95 server.The large-object interface was overhauled. The inversion large objects were the only mechanism for storing large objects. (The inversion file system was removed.)
The instance-level rule system was removed. Rules were still available as rewrite rules.
A short tutorial introducing regularSQL features as well as those ofPostgres95 was distributed with the source code
GNU make (instead ofBSD make) was used for the build. Also,Postgres95 could be compiled with an unpatchedGCC (data alignment of doubles was fixed).
2.3. PostgreSQL#
By 1996, it became clear that the name“Postgres95” would not stand the test of time. We chose a new name,PostgreSQL, to reflect the relationship between the originalPOSTGRES and the more recent versions withSQL capability. At the same time, we set the version numbering to start at 6.0, putting the numbers back into the sequence originally begun by the BerkeleyPOSTGRES project. Postgres is still considered an official project name, both because of tradition and because people find it easier to pronouncePostgres thanPostgreSQL. The emphasis during development ofPostgres95 was on identifying and understanding existing problems in the server code. WithPostgreSQL, the emphasis has shifted to augmenting features and capabilities, although work continues in all areas. Details about what has happened inPostgreSQL since then can be found inAppendix E.