<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.