release.sgml

PostgreSQL7.4.6 for Linux

     Substitute your installation path in the second command.
    </para>

   </sect2>

   <sect2>
    <title>Changes</title>

<itemizedlist>
<listitem><para>Fixed bug in <command>CREATE SCHEMA</command> parsing in ECPG (Michael)</para></listitem>
<listitem><para>Fix compile error when <option>--enable-thread-safety</option> and <option>--with-perl</option> are used together (Peter)</para></listitem>
<listitem><para>Fix for subqueries that used hash joins (Tom)</para>
<para>
    Certain subqueries that used hash joins would crash because of
    improperly shared structures.
</para></listitem>
<listitem><para>Fix free space map compaction bug (Tom)</para>
<para>
    This fixes a bug where compaction of the free space map could lead
    to a database server shutdown.
</para>
</listitem>
<listitem><para>Fix for Borland compiler build of libpq (Bruce)</para></listitem>
<listitem><para>Fix <function>netmask()</function> and <function>hostmask()</function> to return the maximum-length masklen (Tom)</para>
<para>
    Fix these functions to return values consistent with pre-7.4
    releases.
</para>
</listitem>
<listitem><para>Several <filename>contrib/pg_autovacuum</filename> fixes</para>
<para>
    Fixes include improper variable initialization, missing vacuum after
    <command>TRUNCATE</command>, and duration computation overflow for long vacuums.
</para>
</listitem>
<listitem><para>Allow compile of <filename>contrib/cube</filename> under Cygwin (Jason Tishler)</para></listitem>
<listitem><para>Fix Solaris use of password file when no passwords are defined (Tom)</para>
<para>
    Fix crash on Solaris caused by use of any type of password
    authentication when no passwords were defined.
</para>
</listitem>
<listitem><para>JDBC fix for thread problems, other fixes</para></listitem>
<listitem><para>Fix for <type>bytea</type> index lookups (Joe)</para></listitem>
<listitem><para>Fix information schema for bit data types (Peter)</para></listitem>
<listitem><para>Force zero_damaged_pages to be on during recovery from WAL</para></listitem>
<listitem><para>Prevent some obscure cases of <quote>variable not in subplan target lists</quote></para></listitem>
<listitem><para>Make <function>PQescapeBytea</function> and <function>byteaout</function> consistent with each other (Joe)</para></listitem>
<listitem><para>Escape <type>bytea</type> output for bytes > 0x7e(Joe)</para>
<para>
  If different client encodings are used for <type>bytea</type> output and input, it
  is possible for <type>bytea</type> values to be corrupted by the differing
  encodings.  This fix escapes all bytes that might be affected.
</para>
</listitem>
<listitem><para>Added missing <function>SPI_finish()</function> calls to dblink's <function>get_tuple_of_interest()</function> (Joe)</para></listitem>
<listitem><para>New Czech FAQ</para></listitem>
<listitem><para>Fix information schema view <literal>constraint_column_usage</literal> for foreign keys (Peter)</para></listitem>
<listitem><para>ECPG fixes (Michael)</para></listitem>
<listitem><para>Fix bug with multiple <literal>IN</literal> subqueries and joins in the subqueries (Tom)</para></listitem>
<listitem><para>Alllow <literal>COUNT('x')</literal> to work (Tom)</para></listitem>
<listitem><para>Install ECPG include files for Informix compatibility into separate directory (Peter)</para>
<para>
  Some names of ECPG include files for Informix compatibility conflicted with operating system include files.
  By installing them in their own directory, name conflicts have been reduced.
</para>
</listitem>
<listitem><para>Fix SSL memory leak (Neil)</para>
<para>
  This release fixes a bug in 7.4 where SSL didn't free all memory it allocated.
</para>
</listitem>
<listitem><para>Prevent <filename>pg_service.conf</filename> from using service name as default dbname (Bruce)</para></listitem>
<listitem><para>Fix local ident authentication on FreeBSD (Tom)</para></listitem>
</itemizedlist>

  </sect2>
 </sect1>

 <sect1 id="release-7-4">
  <title>Release 7.4</title>

  <note>
   <title>Release date</title>
   <simpara>2003-11-17</simpara>
  </note>

  <sect2>
   <title>Overview</title>

   <para>
    Major changes in this release:

    <variablelist>
     <varlistentry>
      <term>
       <literal>IN</literal> / <literal>NOT IN</literal> subqueries are
       now much more efficient
      </term>

      <listitem>
       <para>
        In previous releases, <literal>IN</literal>/<literal>NOT
        IN</literal> subqueries were joined to the upper query by
        sequentially scanning the subquery looking for a match.  The
        7.4 code uses the same sophisticated techniques used by
        ordinary joins and so is much faster.  An
        <literal>IN</literal> will now usually be as fast as or faster
        than an equivalent <literal>EXISTS</literal> subquery; this
        reverses the conventional wisdom that applied to previous
        releases.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Improved <literal>GROUP BY</literal> processing by using hash buckets
      </term>

      <listitem>
       <para>
        In previous releases, rows to be grouped had to be sorted
        first.  The 7.4 code can do <literal>GROUP BY</literal>
        without sorting, by accumulating results into a hash table
        with one entry per group.  It will still use the sort
        technique, however, if the hash table is estimated to be too
        large to fit in <varname>sort_mem</>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       New multikey hash join capability
      </term>

      <listitem>
       <para>
        In previous releases, hash joins could only occur on single
        keys.  This release allows multicolumn hash joins.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Queries using the explicit <literal>JOIN</literal> syntax are
       now better optimized
      </term>

      <listitem>
       <para>
        Prior releases evaluated queries using the explicit
        <literal>JOIN</literal> syntax only in the order implied by
        the syntax. 7.4 allows full optimization of these queries,
        meaning the optimizer considers all possible join orderings
        and chooses the most efficient.  Outer joins, however, must
        still follow the declared ordering.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Faster and more powerful regular expression code
      </term>

      <listitem>
       <para>
        The entire regular expression module has been replaced with a
        new version by Henry Spencer, originally written for Tcl.  The
        code greatly improves performance and supports several flavors
        of regular expressions.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Function-inlining for simple SQL functions
      </term>

      <listitem>
       <para>
        Simple SQL functions can now be inlined by including their SQL
        in the main query.  This improves performance by eliminating
        per-call overhead.  That means simple SQL functions now
        behave like macros.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Full support for IPv6 connections and IPv6 address data types
      </term>

      <listitem>
       <para>
        Previous releases allowed only IPv4 connections, and the IP
        data types only supported IPv4 addresses. This release adds
        full IPv6 support in both of these areas.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Major improvements in SSL performance and reliability
      </term>

      <listitem>
       <para>
        Several people very familiar with the SSL API have overhauled
        our SSL code to improve SSL key negotiation and error
        recovery.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Make free space map efficiently reuse empty index pages,
       and other free space management improvements
      </term>

      <listitem>
       <para>
        In previous releases, B-tree index pages that were left empty
        because of deleted rows could only be reused by rows with
        index values similar to the rows originally indexed on that
        page. In 7.4, <command>VACUUM</command> records empty index
        pages and allows them to be reused for any future index rows.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       SQL-standard information schema
      </term>

      <listitem>
       <para>
        The information schema provides a standardized and stable way
        to access information about the schema objects defined in a
        database.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Cursors conform more closely to the SQL standard
      </term>

      <listitem>
       <para>
        The commands <command>FETCH</command> and
        <command>MOVE</command> have been overhauled to conform more
        closely to the SQL standard.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Cursors can exist outside transactions
      </term>

      <listitem>
       <para>
        These cursors are also called holdable cursors.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       New client-to-server protocol
      </term>

      <listitem>
       <para>
        The new protocol adds error codes, more status information,
        faster startup, better support for binary data transmission,
        parameter values separated from SQL commands, prepared
        statements available at the protocol level, and cleaner
        recovery from <command>COPY</command> failures.  The older
        protocol is still supported by both server and clients.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       <application>libpq</application> and
       <application>ECPG</application> applications are now fully
       thread-safe
      </term>

      <listitem>
       <para>
        While previous <application>libpq</application> releases
        already supported threads, this release improves thread safety
        by fixing some non-thread-safe code that was used during
        database connection startup.  The <command>configure</command>
        option <option>--enable-thread-safety</option> must be used to
        enable this feature.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       New version of full-text indexing
      </term>

      <listitem>
       <para>
        A new full-text indexing suite is available in
        <filename>contrib/tsearch2</filename>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       New autovacuum tool
      </term>

      <listitem>
       <para>
        The new autovacuum tool in
        <filename>contrib/autovacuum</filename> monitors the database
        statistics tables for
        <command>INSERT</command>/<command>UPDATE</command>/<command>DELETE</command>
        activity and automatically vacuums tables when needed.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>
       Array handling has been improved and moved into the server core
      </term>

      <listitem>
       <para>
        Many array limitations have been removed, and arrays behave
        more like fully-supported data types.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
  </sect2>

  <sect2>
   <title>Migration to version 7.4</title>
                                      
   <para>
    A dump/restore using <application>pg_dump</application> is
    required for those wishing to migrate data from any previous
    release.
   </para>
   
   <para>
    Observe the following incompatibilities:

    <itemizedlist>
     <listitem>
      <para>
       The server-side autocommit setting was removed and
       reimplemented in client applications and languages.
       Server-side autocommit was causing too many problems with
       languages and applications that wanted to control their own
       autocommit behavior, so autocommit was removed from the server
       and added to individual client APIs as appropriate.
      </para>
     </listitem>

     <listitem>
      <para>
       Error message wording has changed substantially in this
       release.  Significant effort was invested to make the messages
       more consistent and user-oriented.  If your applications try to
       detect different error conditions by parsing the error message,
       you are strongly encouraged to use the new error code facility instead.
      </para>
     </listitem>