<!-- $PostgreSQL: pgsql/doc/src/sgml/release-8.5.sgml,v 1.4 2009/08/19 08:18:48 petere Exp $ -->

<sect1 id="release-8.5">
  <title>Release 8.5alpha1</title>
  <sect2>
    <title>Overview</title>
    <para>
      PostgreSQL alpha releases are snapshots of development code. They
      are intended to preview and test upcoming features and to provide
      the possibility for early feedback. They should not be used in
      production installations or active development projects. While the
      PostgreSQL code is continuously subject to a number of automated
      and manual tests, alpha releases might have serious bugs. Also
      features may be changed incompatibly or removed at any time during
      the development cycle.
    </para>
    <para>
      The development cycle of a PostgreSQL major release alternates
      between periods of development and periods of integration work,
      called commit fests, normally one month each. Alpha releases are
      planned to be produced at the end of every commit fest, thus every
      two months. Since the first commit fest starts within a month from
      the beginning of development altogether, early alpha releases are
      not indicative of the likely feature set of the final release.
    </para>
    <para>
      The release notes below highlight user visible changes and new
      features. There are normally numerous bug fixes and performance
      improvements in every new snapshot of PostgreSQL, and it would be
      too bulky to attempt to list them all. Note that many bug fixes are
      also backported to stable releases of PostgreSQL, and you should be
      using those if you are looking for bug-fix-only upgrades for your
      current installations.
    </para>
  </sect2>
  <sect2>
    <title>Migration</title>
    <para>
      To upgrade from any release to an alpha release or from an alpha
      release to any other release will most likely require a
      dump/restore upgrade procedure. It may happen that this is not
      necessary in particular cases, but that is not verified beforehand.
      (The server will warn you in any case when a dump/restore is
      necessary if you attempt to use it with an old data directory.)
      Note, however, that the dump/restore upgrade procedure is expected
      to work for alpha releases, and problems in this area should be
      reported.
    </para>
  </sect2>
  <sect2>
    <title>Changes</title>
    <sect3>
      <title>SQL Features</title>
      <itemizedlist>
        <listitem>
          <para>
            DROP COLUMN and DROP CONSTRAINT now support an IF EXISTS clause so
            that users can avoid fatal errors when running repeatable scripts.
          </para>
        </listitem>
        <listitem>
          <para>
            UNIQUE constraints can now be DEFERRABLE. This is primarily useful
            for incremental updates of numerical keys, e.g. &quot;ID = ID +
            1&quot;
          </para>
        </listitem>
        <listitem>
          <para>
            Allows parentheses around the query expression that follows a WITH
            clause.
          </para>
        </listitem>
        <listitem>
          <para>
            INFORMATION_SCHEMA, a catalog of standard views of database
            objects, has been updated to the SQL:2008 ANSI/ISO standard.
          </para>
        </listitem>
        <listitem>
          <para>
            Changes character_octet_length to more sensible values in
            INFORMATION_SCHEMA.
          </para>
        </listitem>
        <listitem>
          <para>
            Allow * as parameter for FORCE QUOTE for COPY CSV, so that all
            columns will be quoted.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Performance</title>
      <itemizedlist>
        <listitem>
          <para>
            EXPLAIN allows output of plans in XML or JSON format for automated
            processing of explain plans by analysis or visualization tools.
          </para>
        </listitem>
        <listitem>
          <para>
            EXPLAIN now supports the use of generic options in EXPLAIN ( option
            value, ... ) format, which permits the creation of additional
            EXPLAIN options.
          </para>
        </listitem>
        <listitem>
          <para>
            ALTER TABLE ... ALTER COLUMN ... SET STATISTICS DISTINCT allows
            users to manually tweak the number of distinct values estimated for
            a column, to fix cases where ANALYZE estimates are incorrect.
          </para>
        </listitem>
        <listitem>
          <para>
            Makes GEQO's planning deterministic by having it start from a
            predictable random number seed each time.
          </para>
        </listitem>
        <listitem>
          <para>
            Rewrite GEQO's gimme_tree function so that it always finds a legal
            join sequence. Previously, it could have failed to produce a plan
            in some cases.
          </para>
        </listitem>
        <listitem>
          <para>
            Tweak TOAST code so that columns marked with MAIN storage strategy
            are not forced out-of-line unless that is necessary to make the row
            fit on a page. Previously, they were forced out-of-line if needed
            to get the row down to the default target size (1/4th page).
          </para>
        </listitem>
        <listitem>
          <para>
            Simplify the forms foo &lt;&gt; true and foo &lt;&gt; false to foo
            = false and foo = true during query optimization.
          </para>
        </listitem>
        <listitem>
          <para>
            Avoid per-send() system calls to manage SIGPIPE in libpq, if the
            platform provides either sockopt(SO_NOSIGPIPE) or the MSG_NOSIGNAL
            flag to send().
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Administration and Monitoring</title>
      <itemizedlist>
        <listitem>
          <para>
            Add the ability to include the SQLSTATE error code of any error
            messages in the PostgreSQL activity log with the new
            log_line_prefix placeholder %e.
          </para>
        </listitem>
        <listitem>
          <para>
            Show the exact value being complained of in
            unique-constraint-violation error messages, including unique-index
            build failures.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Security</title>
      <itemizedlist>
        <listitem>
          <para>
            New has_sequence_privilege() functions allow you to check sequence
            privileges for a given ROLE.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Built-In Functions</title>
      <itemizedlist>
        <listitem>
          <para>
            The to_char() formatting functions now supports EEEE (scientific
            notation).
          </para>
        </listitem>
        <listitem>
          <para>
            Use floor() not rint() when reducing precision of fractional
            seconds in timestamp_trunc, timestamptz_trunc, and interval_trunc()
            for the float-datetime case. This improves accuracy of time
            calculations.
          </para>
        </listitem>
        <listitem>
          <para>
            Fix ancient bug in handling of to_char() modifier 'TH', when used
            with HH.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Datatypes</title>
      <itemizedlist>
        <listitem>
          <para>
            New hex-string input and output format options for type BYTEA. Hex
            output format is enabled by default, which is an INCOMPATIBLE
            CHANGE. See the new bytea_output parameter if you need to restore
            compatibility.
          </para>
        </listitem>
        <listitem>
          <para>
            Adds prefix support for text search synonym dictionary, allowing
            creation of synonyms on partial matches.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Server Tools</title>
      <itemizedlist>
        <listitem>
          <para>
            pg_dump/pg_restore --clean now drops large objects.
          </para>
        </listitem>
        <listitem>
          <para>
            Modifies parallel pg_restore ordering logic to avoid a potential
            O(N^2) slowdown for some complex databases.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>psql</title>
      <itemizedlist>
        <listitem>
          <para>
            Have \d show child tables that inherit from the specified parent
          </para>
        </listitem>
        <listitem>
          <para>
            psql now shows the index methods in \di
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Procedural Languages</title>
      <itemizedlist>
        <listitem>
          <para>
            PL/pgSQL functions can now better cope with row types
            containing dropped columns.
          </para>
        </listitem>
        <listitem>
          <para>
            Improves error context reporting in PL/Python, for easier
            debugging.
          </para>
        </listitem>
        <listitem>
          <para>
            Greatly expands the regression testing for PL/Python.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Additional Supplied Modules</title>
      <itemizedlist>
        <listitem>
          <para>
            pgbench is now multi-threaded, allowing it to use multiple CPU's
            for its client connections, and to do more realistic workload
            testing.
          </para>
        </listitem>
        <listitem>
          <para>
            Added the ability to retrieve asynchronous notifications using
            dblink, via the addition of the function dblink_get_notify().
          </para>
        </listitem>
        <listitem>
          <para>
            Added matchorig, matchsynonyms, and keepsynonyms options to
            contrib/dict_xsyn.
          </para>
        </listitem>
        <listitem>
          <para>
            Added contrib/unaccent.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Development</title>
      <itemizedlist>
        <listitem>
          <para>
            Functions which conflict with C++ reserved words have been renamed,
            making backend header files now safe to use with C++ libraries.
          </para>
        </listitem>
        <listitem>
          <para>
            Add man pages for SPI functions.
          </para>
        </listitem>
        <listitem>
          <para>
            ECPG now includes a STRING datatype for Informix compatibility
            mode.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Ports</title>
      <itemizedlist>
        <listitem>
          <para>
            Reserve the shared memory region during backend startup on Windows,
            so that memory allocated by starting third party DLLs doesn't end
            up conflicting with it. Hopefully this solves the long-time issue
            with &quot;could not reattach to shared memory&quot; errors on
            Win32.
          </para>
        </listitem>
        <listitem>
          <para>
            Add s_lock support for SuperH architecture (not well tested).
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Source code, build options</title>
      <itemizedlist>
        <listitem>
          <para>
            Upgrade to Autoconf 2.63 (not relevant to users of distribution
            tarballs).
          </para>
        </listitem>
        <listitem>
          <para>
            Minimum version of Flex is now 2.5.31, to support reentrant
            scanners (not relevant to users of distribution tarballs).
          </para>
        </listitem>
        <listitem>
          <para>
            Documentation build rules have been improved. The generated
            documentation files are now shipped &quot;loose&quot;, not in
            sub-tarballs.
          </para>
        </listitem>
        <listitem>
          <para>
            New toolchain to generate man pages. From now on, the man pages
            will be current in every release.
          </para>
        </listitem>
        <listitem>
          <para>
            Code-coverage testing support now extends to the entire source
            tree, not only src/backend/.
          </para>
        </listitem>
        <listitem>
          <para>
            Make the core scanner re-entrant, along with additional fixes that
            will let it be used directly by PL/pgSQL.
          </para>
        </listitem>
        <listitem>
          <para>
            Fix backend startup to not depend on the flat-file copy of
            pg_database. This is a first step towards eliminating the flat
            files altogether.
          </para>
        </listitem>
      </itemizedlist>
    </sect3>
  </sect2>
</sect1>
