<!-- doc/src/sgml/history.sgml -->

<sect1 id="history">
 <title>A Brief History of <productname>PostgreSQL</productname></title>

 <indexterm zone="history">
  <primary>history</primary>
  <secondary>of PostgreSQL</secondary>
 </indexterm>

 <para>
  The object-relational database management system now known as
  <productname>PostgreSQL</productname> is derived from the
  <productname>POSTGRES</productname> package written at the
  University of California at Berkeley.  With decades of
  development behind it, <productname>PostgreSQL</productname> is now
  the most advanced open-source database available anywhere.
 </para>

 <para>
  Another take on the history presented here can be found in Dr. Joe
  Hellerstein's paper <quote>Looking Back at Postgres</quote>
  <xref linkend="hell18"/>.
 </para>

 <sect2 id="history-berkeley">
  <title>The Berkeley <productname>POSTGRES</productname> Project</title>

  <indexterm zone="history-berkeley">
   <primary>POSTGRES</primary>
  </indexterm>

  <para>
   The <productname>POSTGRES</productname> project, led by Professor
   Michael Stonebraker, was sponsored by the Defense Advanced Research
   Projects Agency (<acronym>DARPA</acronym>), the Army Research
   Office (<acronym>ARO</acronym>), the National Science Foundation
   (<acronym>NSF</acronym>), and ESL, Inc.  The implementation of
   <productname>POSTGRES</productname> began in 1986.  The initial
   concepts for the system were presented in <xref linkend="ston86"/>,
   and the definition of the initial data model appeared in <xref
   linkend="rowe87"/>.  The design of the rule system at that time was
   described in <xref linkend="ston87a"/>.  The rationale and
   architecture of the storage manager were detailed in <xref
   linkend="ston87b"/>.
  </para>

  <para>
   <productname>POSTGRES</productname> has undergone several major
   releases since then.  The first <quote>demoware</quote> system
   became operational in 1987 and was shown at the 1988
   <acronym>ACM-SIGMOD</acronym> Conference.  Version 1, described in
   <xref linkend="ston90a"/>, was released to a few external users in
   June 1989.  In response to a critique of the first rule system
   (<xref linkend="ston89"/>), the rule system was redesigned (<xref
   linkend="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
   until <productname>Postgres95</productname> (see below) focused on
   portability and reliability.
  </para>

  <para>
   <productname>POSTGRES</productname> 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.
   <productname>POSTGRES</productname> has also been used as an
   educational tool at several universities.  Finally, Illustra
   Information Technologies (later merged into
   <ulink url="https://www.ibm.com/analytics/informix"><productname>Informix</productname></ulink>,
   which is now owned by <ulink
   url="https://www.ibm.com/">IBM</ulink>) picked up the code and
   commercialized it.  In late 1992,
   <productname>POSTGRES</productname> became the primary data manager
   for the Sequoia 2000 scientific computing project described in
   <xref linkend="ston92"/>.
  </para>

  <para>
   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 Berkeley
   <productname>POSTGRES</productname> project officially ended with
   Version 4.2.
  </para>
 </sect2>

 <sect2 id="history-postgres95">
  <title><productname>Postgres95</productname></title>

  <indexterm zone="history-postgres95">
   <primary>Postgres95</primary>
  </indexterm>

  <para>
   In 1994, Andrew Yu and Jolly Chen added an SQL language interpreter
   to <productname>POSTGRES</productname>.  Under a new name,
   <productname>Postgres95</productname> was subsequently released to
   the web to find its own way in the world as an open-source
   descendant of the original <productname>POSTGRES</productname>
   Berkeley code.
  </para>

  <para>
   <productname>Postgres95</productname> code was completely ANSI C
   and trimmed in size by 25%. Many internal changes improved
   performance and
   maintainability. <productname>Postgres95</productname> release
   1.0.x ran about 30&ndash;50% faster on the Wisconsin Benchmark compared
   to <productname>POSTGRES</productname>, Version 4.2.  Apart from
   bug fixes, the following were the major enhancements:

   <itemizedlist>
    <listitem>
     <para>
      The query language PostQUEL was replaced with
      <acronym>SQL</acronym> (implemented in the server).  (Interface
      library <link linkend="libpq">libpq</link> was named after PostQUEL.)
      Subqueries
      were not supported until <productname>PostgreSQL</productname>
      (see below), but they could be imitated in
      <productname>Postgres95</productname> with user-defined
      <acronym>SQL</acronym> functions. Aggregate functions were
      re-implemented.  Support for the <literal>GROUP BY</literal>
      query clause was also added.
     </para>
    </listitem>

    <listitem>
     <para>
      A new program
      (<application>psql</application>) was provided for interactive
      SQL queries, which used <acronym>GNU</acronym>
      <application>Readline</application>.  This largely superseded
      the old <application>monitor</application> program.
     </para>
    </listitem>

    <listitem>
     <para>
      A new front-end library, <filename>libpgtcl</filename>,
      supported <acronym>Tcl</acronym>-based clients.  A sample shell,
      <command>pgtclsh</command>, provided new Tcl commands to
      interface <application>Tcl</application> programs with the
      <productname>Postgres95</productname> server.
     </para>
    </listitem>

    <listitem>
     <para>
      The large-object interface was overhauled. The inversion large
      objects were the only mechanism for storing large objects.  (The
      inversion file system was removed.)
     </para>
    </listitem>

    <listitem>
     <para>
      The instance-level rule system was removed.  Rules were still
      available as rewrite rules.
     </para>
    </listitem>

    <listitem>
     <para>
      A short tutorial introducing regular <acronym>SQL</acronym>
      features as well as those of
      <productname>Postgres95</productname> was distributed with the
      source code.
     </para>
    </listitem>

    <listitem>
     <para>
      <acronym>GNU</acronym> make (instead of <acronym>BSD</acronym>
      make) was used for the build.  Also,
      <productname>Postgres95</productname> could be compiled with an
      unpatched <productname>GCC</productname> (data alignment of
      doubles was fixed).
     </para>
    </listitem>
   </itemizedlist>
  </para>
 </sect2>

 <sect2 id="history-postgresql">
  <title><productname>PostgreSQL</productname></title>

  <para>
   By 1996, it became clear that the name <quote>Postgres95</quote>
   would not stand the test of time. We chose a new name,
   <productname>PostgreSQL</productname>, to reflect the relationship
   between the original <productname>POSTGRES</productname> and the
   more recent versions with <acronym>SQL</acronym> 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
   Berkeley <productname>POSTGRES</productname> project.
  </para>

  <para>
   <productname>Postgres</productname> is still considered an official
   project name, both because of tradition and because people find it
   easier to pronounce <productname>Postgres</productname> than
   <productname>PostgreSQL</productname>.
  </para>

  <para>
   The emphasis during development of
   <productname>Postgres95</productname> was on identifying and
   understanding existing problems in the server code.  With
   <productname>PostgreSQL</productname>, the emphasis has shifted to
   augmenting features and capabilities, although work continues in
   all areas.
  </para>

  <para>
   Details about what has happened in
   each <productname>PostgreSQL</productname> release since then
   can be found at
   <ulink url="https://www.postgresql.org/docs/release/">https://www.postgresql.org/docs/release/</ulink>.
  </para>
 </sect2>
</sect1>
