<!-- doc/src/sgml/release-9.1.sgml -->
<!-- See header comment in release.sgml about typical markup -->

 <sect1 id="release-9-1">
  <title>Release 9.1</title>

  <note>
   <title>Release Date</title>
   <simpara>2011-??-??</simpara>
  </note>

  <para>CURRENT AS OF 2011-07-07</para>

  <sect2>
   <title>Overview</title>

   <para>
    This release shows <productname>PostgreSQL</> moving beyond the
    traditional relational feature set with new, ground-breaking
    functionality that is unique to <productname>PostgreSQL</>.
    Additionally, this release improves streaming replication by adding
    a synchronous option and monitoring improvements.  Major enhancements
    include:
   </para>

   <itemizedlist>

    <!-- This list duplicates items below, but without authors or details-->

    <listitem>
     <para>
      Support unlogged tables using the <link
      linkend="SQL-CREATETABLE-description"><literal>UNLOGGED</></link>
      option in <link linkend="SQL-CREATETABLE"><command>CREATE
      TABLE</></link>
     </para>
    </listitem>

    <listitem>
     <para>
      Allow <link linkend="synchronous-replication">synchronous
      replication</link>
     </para>
    </listitem>

    <listitem>
     <para>
      Add support for <link linkend="SQL-CREATEFOREIGNTABLE">foreign
      tables</link>
     </para>
    </listitem>

    <listitem>
     <para>
      Add per-column <link
      linkend="collation">collation</link> support
     </para>
    </listitem>

    <listitem>
     <para>
      Add a <link linkend="SQL-SECURITY-LABEL"><command>SECURITY
      LABEL</></link> command
     </para>
    </listitem>

    <listitem>
     <para>
      Add a true <link
      linkend="xact-serializable">serializable</link> isolation
      level
     </para>
    </listitem>

    <listitem>
     <para>
      Allow data-modification commands
      (<command>INSERT</>/<command>UPDATE</>/<command>DELETE)</> in
      <link linkend="queries-with"><literal>WITH</></link> clauses
     </para>
    </listitem>

    <listitem>
     <para>
      Add nearest-neighbor (order-by-operator) searching to <link
      linkend="GiST"><acronym>GiST</> indexes</link>
     </para>
    </listitem>

    <listitem>
     <para>
      Add <link linkend="extend-extensions">extensions</link> which
      simplify packaging of additions to <productname>PostgreSQL</>
     </para>
    </listitem>

    <listitem>
     <para>
      Update the <link linkend="plpython">PL/Python</link> server-side
      language
     </para>
    </listitem>

   </itemizedlist>

   <para>
    The above items are explained in more detail in the sections below.
   </para>

  </sect2>

  <sect2>

  <title>Migration to Version 9.1</title>

   <para>
    A dump/restore using <application>pg_dump</application>,
    or use of <application>pg_upgrade</application>, is required
    for those wishing to migrate data from any previous
    release.
   </para>

   <para>
    Version 9.1 contains a number of changes that may affect compatibility
    with previous releases.  Observe the following incompatibilities:
   </para>

   <sect3>
    <title>Strings</title>

    <itemizedlist>

     <listitem>
      <para>
       Change the default value of <link
       linkend="guc-standard-conforming-strings"><varname>standard_conforming_strings</></link>
       to on (Robert Haas)
      </para>

      <para>
       By default, backslashes are now ordinary characters in string literals,
       not escape characters.  This change removes a long-standing
       incompatibility with the SQL standard.  <link
       linkend="guc-escape-string-warning"><varname>escape_string_warning</></link>
       has produced warnings about this usage for years.  <literal>E''</>
       strings are the proper way to embed backslash escapes in strings and are
       unaffected by this change.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Casting</title>

    <itemizedlist>

     <listitem>
      <para>
       Disallow function-style and attribute-style data type casts for
       composite types (Tom Lane)
      </para>

      <para>
       For example, disallow
       <literal><replaceable>composite_value</>.text</literal> and
       <literal>text(<replaceable>composite_value</>)</literal>.
       Unintentional uses of this syntax have frequently resulted in bug
       reports; although it was not a bug, it seems better to go back to
       rejecting such expressions.
       The <literal>CAST</> and <literal>::</> syntaxes are still available
       for use when a cast of an entire composite value is actually intended.
      </para>
     </listitem>

     <listitem>
      <para>
       Tighten casting checks for domains based on arrays (Tom Lane)
      </para>

      <para>
       When a domain is based on an array type, it is allowed to <quote>look
       through</> the domain type to access the array elements, including
       subscripting the domain value to fetch or assign an element.
       Assignment to an element of such a domain value, for instance via
       <literal>UPDATE ... SET domaincol[5] = ...</>, will now result in
       rechecking the domain type's constraints, whereas before the checks
       were skipped.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Arrays</title>

    <itemizedlist>

     <listitem>
      <para>
       Change <link
       linkend="array-functions-table"><function>string_to_array()</></link>
       to return an empty array for a zero-length string (Pavel
       Stehule)
      </para>

      <para>
       Previously this returned a null value.
      </para>
     </listitem>

     <listitem>
      <para>
       Change <link
       linkend="array-functions-table"><function>string_to_array()</></link>
       so a <literal>NULL</> separator splits the string into characters
       (Pavel Stehule)
      </para>

      <para>
       Previously this returned a null value.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Object Modification</title>

    <itemizedlist>

     <listitem>
      <para>
       Fix improper checks for before/after triggers (Tom Lane)
      </para>

      <para>
       Triggers can now be fired in three cases: <literal>BEFORE</>,
       <literal>AFTER</>, or <literal>INSTEAD OF</> some action.
       Trigger function authors should verify that their logic behaves
       sanely in all three cases.
      </para>
     </listitem>

     <listitem>
      <para>
        Require superuser or <literal>CREATEROLE</> permissions in order to
        set role comments (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Server Settings</title>

    <itemizedlist>

     <listitem>
      <para>
       Change <link
       linkend="functions-recovery-info-table"><function>pg_last_xlog_receive_location()</></link>
       so it never moves backwards (Fujii Masao)
      </para>

      <para>
       Previously <function>pg_last_xlog_receive_location()</> could
       move backward when streaming replication is restarted.
      </para>
     </listitem>

     <listitem>
      <para>
       Have logging of replication connections honor <link
       linkend="guc-log-connections"><varname>log_connections</></link>
       (Magnus Hagander)
      </para>

      <para>
       Previously replication connections were always logged.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title><link linkend="plpgsql">PL/pgSQL</link> Server-Side Language</title>

    <itemizedlist>

     <listitem>
      <para>
       Change PL/pgSQL's <literal>RAISE</> command without parameters
       to be catchable by the attached exception block (Piyush Newe)
      </para>

      <para>
       Previously <literal>RAISE</> in a code block was always scoped to
       an attached exception block, so it was uncatchable at the same
       scope.
      </para>
     </listitem>

     <listitem>
      <para>
       Adjust PL/pgSQL's error line numbering code to be consistent
       with other PLs (Pavel Stehule)
      </para>

      <para>
       Previously, PL/pgSQL would ignore (not count) an empty line at the
       start of the function body.  Since this was inconsistent with all
       other languages, the special case was removed.
      </para>
     </listitem>

     <listitem>
      <para>
       Make PL/pgSQL complain about conflicting IN and OUT parameter names
       (Tom Lane)
      </para>

      <para>
       Formerly, the collision was not detected, and the name would just
       silently refer to only the OUT parameter.
      </para>
     </listitem>

     <listitem>
      <para>
       Type modifiers of PL/pgSQL variables are now visible to the SQL parser
       (Tom Lane)
      </para>

      <para>
       A type modifier (such as a varchar length limit) attached to a PL/pgSQL
       variable was formerly enforced during assignments, but was ignored for
       all other purposes.  Such variables will now behave more like table
       columns declared with the same modifier.  This is not expected to make
       any visible difference in most cases, but it could result in subtle
       changes for some SQL commands issued by PL/pgSQL functions.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Other Incompatibilities</title>

    <itemizedlist>

     <listitem>
      <para>
       Make <link
       linkend="monitoring-stats-funcs-table"><function>pg_stat_reset()</></link>
       reset all database-level statistics (Tomas Vondra)
      </para>

      <para>
       Some <structname>pg_stat_database</> counters were not being reset.
      </para>
     </listitem>

     <listitem>
      <para>
        Fix some <link
        linkend="infoschema-triggers"><structname>information_schema.triggers</></link>
        column names to match the new SQL-standard names (Dean Rasheed)
      </para>
     </listitem>

     <listitem>
      <para>
       Treat <application>ECPG</> cursor names as case-insensitive (Zoltan Boszormenyi)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>
  </sect2>

  <sect2>
   <title>Changes</title>
    <para>
     Version 9.1 has ...
    </para>

   <sect3>
    <title>Server</title>

    <sect4>
     <title>Performance</title>

     <itemizedlist>

      <listitem>
       <para>
        Support unlogged tables using the <link
        linkend="SQL-CREATETABLE-description"><literal>UNLOGGED</></link>
        option in <link linkend="SQL-CREATETABLE"><command>CREATE
        TABLE</></link> (Robert Haas)
       </para>

       <para>
        Such tables provide better update performance than regular tables,
        but are not crash-safe: their contents are automatically cleared in
        case of a server crash.  Their contents do not propagate to
        replication slaves, either.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <literal>FULL OUTER JOIN</literal> to be implemented as a
        hash join, and allow either side of a <literal>LEFT OUTER JOIN</>
        or <literal>RIGHT OUTER JOIN</> to be hashed (Tom Lane)
       </para>

       <para>
        Previously <literal>FULL OUTER JOIN</literal> could only be
        implemented as a merge join, and <literal>LEFT OUTER JOIN</literal>
        and <literal>RIGHT OUTER JOIN</literal> could hash only the nullable
        side of the join.  These changes provide additional query optimization
        possibilities.
       </para>
      </listitem>

      <listitem>
       <para>
         Merge duplicate fsync requests on busy systems (Robert Haas,
         Greg Smith)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve performance of <link
        linkend="guc-commit-siblings"><varname>commit_siblings</></link>
        (Greg Smith)
       </para>

       <para>
        This allows the use of <varname>commit_siblings</varname> with
        less overhead.
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce the memory requirement for large ispell dictionaries
        (Pavel Stehule, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Avoid leaving data files open after <quote>blind writes</>
        (Alvaro Herrera)
       </para>

       <para>
        This fixes scenarios where backends might hold open files that
        were long since deleted, preventing the kernel from reclaiming
        disk space.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Optimizer</title>

     <itemizedlist>

      <listitem>
       <para>
        Allow inheritance table scans to return meaningfully-sorted
        results (Greg Stark, Hans-Jurgen Schonig, Robert Haas, Tom Lane)
       </para>

       <para>
        This allows better optimization of queries that use <literal>ORDER
        BY</>, <literal>LIMIT</>, or <literal>MIN</>/<literal>MAX</> with
        inherited tables.
       </para>
      </listitem>

      <listitem>
       <para>
         Improve GIN index scan cost estimation (Teodor Sigaev)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve cost estimation for aggregates and window functions (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Authentication</title>

     <itemizedlist>

      <listitem>
       <para>
        Support host names and host suffixes
        (e.g. <literal>.example.com</>) in <link
        linkend="auth-pg-hba-conf"><filename>pg_hba.conf</></link>
        (Peter Eisentraut)
       </para>

       <para>
        Previously only host <acronym>IP</> addresses and <acronym>CIDR</>
        values were supported.
       </para>
      </listitem>

      <listitem>
       <para>
        Support the key word <literal>all</> in the host column of <link
        linkend="auth-pg-hba-conf"><filename>pg_hba.conf</></link>
        (Peter Eisentraut)
       </para>

       <para>
        Previously people used <literal>0.0.0.0/0</> or <literal>::/0</>
        for this.
       </para>
      </listitem>

      <listitem>
       <para>
        Reject <literal>local</> lines in <link
        linkend="auth-pg-hba-conf"><filename>pg_hba.conf</></link>
        on platforms that don't support Unix-socket connections
        (Magnus Hagander)
       </para>

       <para>
        Formerly, such lines were silently ignored, which could be surprising.
        This makes the behavior more like other unsupported cases.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="gssapi-auth"><acronym>GSSAPI</></link>
        to be used to authenticate to servers via <link
        linkend="sspi-auth"><acronym>SSPI</></link> (Christian Ullrich)
       </para>

       <para>
        Specifically this allows Unix-based <acronym>GSSAPI</> clients
        to do <acronym>SSPI</> authentication with Windows servers.
       </para>
      </listitem>

      <listitem>
       <para>
        <link linkend="auth-ident"><literal>ident</literal></link>
        authentication over local sockets is now known as
        <link linkend="auth-peer"><literal>peer</literal></link>
        (Magnus Hagander)
       </para>

       <para>
        The old term is still accepted for backward compatibility.
       </para>
      </listitem>

      <listitem>
       <para>
        Rewrite <link linkend="auth-peer"><acronym>peer</></link>
        authentication to avoid use of credential control messages (Tom Lane)
       </para>

       <para>
        This change makes the peer authentication code simpler and
        better-performing.  However, it requires the platform to provide the
        <function>getpeereid</> function or an equivalent socket operation.
        So far as is known, the only platform for which peer authentication
        worked before and now will not is pre-5.0 NetBSD.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Monitoring</title>

     <itemizedlist>

      <listitem>
       <para>
        Add details to the logging of restartpoints and checkpoints,
        which is controlled by <link
        linkend="guc-log-checkpoints"><varname>log_checkpoints</></link>
        (Fujii Masao, Greg Smith)
       </para>

       <para>
        New details show <acronym>WAL</> file and sync activity.
       </para>
      </listitem>

      <listitem>
       <para>
         Add <link
         linkend="guc-log-file-mode"><varname>log_file_mode</></link>
         which controls the permissions on log files created by the
         logging collector (Martin Pihlak)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Statistical Views</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <structfield>client_hostname</structfield> column to <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_activity</></link>
        (Peter Eisentraut)
       </para>

       <para>
        Previously only the client address was reported.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_xact_*</></link>
        statistics functions and views (Joel Jacobson)
       </para>

       <para>
        These are like the database-wide statistics counter views, but
        reflect counts for only the current transaction.
       </para>
      </listitem>

      <listitem>
       <para>
         Add time of last reset in database-level and background writer
         statistics views (Tomas Vondra)
       </para>
      </listitem>

      <listitem>
       <para>
         Add columns showing the number of vacuum and analyze operations
         in <link
         linkend="monitoring-stats-views-table"><structname>pg_stat_*_tables</></link>
         views (Magnus Hagander)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <structfield>buffers_backend_fsync</> column to <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_bgwriter</></link>
        (Greg Smith)
       </para>

       <para>
        This new column counts the number of times a backend fsyncs a
        buffer.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Server Settings</title>

     <itemizedlist>

      <listitem>
       <para>
        Allow auto-tuning of <link
        linkend="guc-wal-buffers"><varname>wal_buffers</></link> (Greg
        Smith)
       </para>

       <para>
        <varname>wal_buffers</> is now auto-tuned by default based on
        the size of <varname>shared_buffers</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Increase the maximum values for
        <link linkend="guc-deadlock-timeout"><varname>deadlock_timeout</varname></link>,
        <link linkend="guc-log-min-duration-statement"><varname>log_min_duration_statement</varname></link>, and
        <link linkend="guc-log-autovacuum-min-duration"><varname>log_autovacuum_min_duration</varname></link>
        (Peter Eisentraut)
       </para>

       <para>
        The maximum value for each of these parameters was previously
        only about 35 minutes.  Much larger values are now allowed.
       </para>
      </listitem>

      </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Replication and Recovery</title>

   <sect4>
    <title>Streaming Replication and Continuous Archiving</title>

    <itemizedlist>

     <listitem>
      <para>
       Allow <link linkend="synchronous-replication">synchronous
       replication</link> (Simon Riggs, Fujii Masao)
      </para>

      <para>
       This allows the primary to wait for a standby to write the transaction
       information to disk before acknowledging the commit.
       One standby at a time can take the role of the synchronous standby,
       as controlled by the
       <link linkend="guc-synchronous-standby-names"><varname>synchronous_standby_names</varname></link>
       setting.  Synchronous replication can be enabled or disabled on a
       per-transaction basis using the
       <link linkend="guc-synchronous-commit"><varname>synchronous_commit</></link>
       setting.
      </para>
     </listitem>

     <listitem>
      <para>
       Add protocol support for sending file system backups to standbys using
       the streaming replication network connection (Magnus Hagander,
       Heikki Linnakangas)
      </para>

      <para>
       This avoids the requirement of manually transferring a file
       system backup when setting up a standby server.
      </para>
     </listitem>

     <listitem>
      <para>
       Add
       <link linkend="guc-replication-timeout"><varname>replication_timeout</></link>
       setting (Fujii Masao, Heikki Linnakangas)
      </para>

      <para>
       Replication connections that are idle for more than the
       <varname>replication_timeout</> interval will be terminated
       automatically.  Formerly, a failed connection was typically not
       detected until the TCP timeout elapsed, which is inconveniently
       long in many situations.
      </para>
     </listitem>

     <listitem>
      <para>
       Add command-line tool <link
       linkend="app-pgbasebackup"><application>pg_basebackup</></link>
       for creating a new standby server or database backup (Magnus
       Hagander)
      </para>
     </listitem>

     <listitem>
      <para>
       Add replication <link linkend="SQL-CREATEROLE">permission</link>
       for roles (Magnus Hagander)
      </para>

      <para>
       This is a read-only permission used for streaming replication.
       It allows a non-superuser role to be used for replication connections.
       Previously only superusers could initiate replication
       connections; superusers still have this permission by default.
      </para>
     </listitem>

    </itemizedlist>

    </sect4>

    <sect4>
     <title>Replication Monitoring</title>

     <itemizedlist>

      <listitem>
       <para>
        Add system view <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_replication</></link>
        which displays activity of <acronym>WAL</> sender processes (Itagaki
        Takahiro, Simon Riggs)
       </para>

       <para>
        This reports the status of all connected standby servers.
       </para>
      </listitem>

      <listitem>
       <para>
        Add monitoring function <link
        linkend="functions-recovery-info-table"><function>pg_last_xact_replay_timestamp()</></link>
        (Fujii Masao)
       </para>

       <para>
        This returns the time at which the primary generated the most
        recent commit or abort record applied on the standby.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Hot Standby</title>

     <itemizedlist>

     <listitem>
      <para>
       Add configuration parameter <link
       linkend="guc-hot-standby-feedback"><varname>hot_standby_feedback</></link>
       to enable standbys to postpone cleanup of old row versions on the
       primary (Simon Riggs)
      </para>

      <para>
       This helps avoid canceling long-running queries on the standby.
      </para>
     </listitem>

      <listitem>
       <para>
        Add the <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_database_conflicts</></link>
        system view to show queries that have been canceled and the
        reason (Magnus Hagander)
       </para>

       <para>
        Cancellations can occur because of dropped tablespaces, lock
        timeouts, old snapshots, pinned buffers, and deadlocks.
       </para>
      </listitem>

      <listitem>
       <para>
        Add a <structfield>conflicts</> count to <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_database</></link>
        (Magnus Hagander)
       </para>

       <para>
        This is the number of conflicts that occurred in the database.
       </para>
      </listitem>

      <listitem>
       <para>
        Increase the maximum values for
        <link linkend="guc-max-standby-archive-delay"><varname>max_standby_archive_delay</varname></link> and
        <link linkend="guc-max-standby-streaming-delay"><varname>max_standby_streaming_delay</varname></link>.
       </para>

       <para>
        The maximum value for each of these parameters was previously
        only about 35 minutes.  Much larger values are now allowed.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link
        linkend="errcodes-table"><literal>ERRCODE_T_R_DATABASE_DROPPED</></link>
        error code to report recovery conflicts due to dropped databases
        (Tatsuo Ishii)
       </para>

       <para>
        This is useful for connection pooling software.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Recovery Control</title>

     <itemizedlist>

      <listitem>
       <para>
        Add functions to control streaming replication replay (Simon Riggs)
       </para>

       <para>
        The new functions are <link
        linkend="functions-recovery-control-table"><function>pg_xlog_replay_pause()</></link>,
        <link
        linkend="functions-recovery-control-table"><function>pg_xlog_replay_resume()</></link>,
        and the status function <link
        linkend="functions-recovery-control-table"><function>pg_is_xlog_replay_paused()</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <filename>recovery.conf</> setting <link
        linkend="pause-at-recovery-target"><varname>pause_at_recovery_target</></link>
        to pause recovery at target (Simon Riggs)
       </para>

       <para>
        This allows a recovery server to be queried to check whether
        the recovery point is the one desired.
       </para>
      </listitem>

      <listitem>
       <para>
        Add the ability to create named restore points using <link
        linkend="functions-admin-backup-table"><function>pg_create_restore_point()</></link>
        (Jaime Casanova)
       </para>

       <para>
        These named restore points can be specified as recovery
        targets using the new <filename>recovery.conf</> setting
        <link linkend="recovery-target-name"><varname>recovery_target_name</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow standby recovery to switch to a new timeline automatically
        (Heikki Linnakangas)
       </para>

       <para>
        Now standby servers scan the archive directory for new
        timelines periodically.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link
        linkend="guc-restart-after-crash"><varname>restart_after_crash</></link>
        setting which disables automatic server restart after a backend
        crash (Robert Haas)
       </para>

       <para>
        This allows external cluster management software to take control
        of whether servers restart or not.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link
        linkend="recovery-config"><filename>recovery.conf</></link>
        to use the same quoting behavior as <filename>postgresql.conf</>
        (Dimitri Fontaine)
       </para>

       <para>
        Previously all values had to be quoted.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Queries</title>

     <itemizedlist>

      <listitem>
       <para>
        Add a true <link
        linkend="xact-serializable">serializable</link> isolation
        level (Kevin Grittner, Dan Ports)
       </para>

       <para>
        Previously, asking for serializable isolation guaranteed only that a
        single MVCC snapshot would be used for the entire transaction, which
        allowed certain documented anomalies.  The old snapshot isolation
        behavior is still accessible by requesting the <link
        linkend="xact-repeatable-read"><literal>REPEATABLE READ</></link>
        isolation level.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow data-modification commands
        (<command>INSERT</>/<command>UPDATE</>/<command>DELETE)</> in
        <link linkend="queries-with"><literal>WITH</></link> clauses
        (Marko Tiikkaja, Hitoshi Harada)
       </para>

       <para>
        These commands can use <literal>RETURNING</> to pass data up to the
        containing query.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="queries-with"><literal>WITH</></link>
        clauses to be attached to <command>INSERT</>, <command>UPDATE</>,
        <command>DELETE</> statements (Marko Tiikkaja, Hitoshi Harada)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow non-<link linkend="queries-group"><literal>GROUP
        BY</></link> columns in the query target list when the primary
        key is specified in the <literal>GROUP BY</> clause (Peter
        Eisentraut)
       </para>

       <para>
        Some other database system already allowed this behavior, and
        because of the primary key, the result is unambiguous.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow use of the key word <literal>DISTINCT</> in <link
        linkend="queries-union"><literal>UNION</>/<literal>INTERSECT</>/<literal>EXCEPT</></link>
        clauses (Tom Lane)
       </para>

       <para>
        <literal>DISTINCT</> is the default behavior so use of this
        key word is redundant, but the SQL standard allows it.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix ordinary queries with rules to use the same snapshot behavior
        as <command>EXPLAIN ANALYZE</> (Marko Tiikkaja)
       </para>

       <para>
        Previously <command>EXPLAIN ANALYZE</> used a slightly different
        snapshot for queries involving rules.  The <command>EXPLAIN ANALYZE</>
        behavior was judged to be more logical.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Strings</title>

     <itemizedlist>

      <listitem>
       <para>
        Add per-column <link
        linkend="collation">collation</link> support
        (Peter Eisentraut, Tom Lane)
       </para>

       <para>
        Previously collation could only be set at database creation.
        Collation can now be set per column, domain, index, or
        expression, via the SQL-standard <literal>COLLATE</> clause.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Object Manipulation</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="extend-extensions">extensions</link> which
        simplify packaging of additions to <productname>PostgreSQL</>
        (Dimitri Fontaine, Tom Lane)
       </para>

       <para>
        Extensions are controlled by the new <link
        linkend="SQL-CREATEEXTENSION"><command>CREATE</></link>/<link
        linkend="SQL-ALTEREXTENSION"><command>ALTER</></link>/<link
        linkend="SQL-DROPEXTENSION"><command>DROP EXTENSION</></link>
        commands.  This replaces ad-hoc methods of grouping objects that
        are added to a <productname>PostgreSQL</> installation.
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for <link linkend="SQL-CREATEFOREIGNTABLE">foreign
        tables</link> (Shigeru Hanada, Robert Haas, Jan Urbanski,
        Heikki Linnakangas)
       </para>

       <para>
        This allows data stored outside the database to be used like
        native <productname>PostgreSQL</>-stored data.  Foreign tables
        are currently read-only, however.
       </para>
      </listitem>

     <listitem>
      <para>
         Allow new values to be added to an existing enum type via
         <link linkend="SQL-ALTERTYPE"><command>ALTER TYPE</></link> (Andrew
         Dunstan)
      </para>
     </listitem>

      <listitem>
       <para>
        Add <link linkend="SQL-ALTERTYPE"><command>ALTER TYPE ...
        ADD/DROP/ALTER/RENAME ATTRIBUTE</></link> (Peter Eisentraut)
       </para>

       <para>
        This allows modification of composite types.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title><command>ALTER</> Object</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <literal>RESTRICT</>/<literal>CASCADE</> to <link
        linkend="SQL-ALTERTYPE"><command>ALTER TYPE</></link> operations
        on typed tables (Peter Eisentraut)
       </para>

       <para>
        This controls
        <literal>ADD</>/<literal>DROP</>/<literal>ALTER</>/<literal>RENAME
        ATTRIBUTE</> cascading behavior.
       </para>
      </listitem>

      <listitem>
       <para>
        Support <literal>ALTER TABLE <replaceable>name</> {OF | NOT OF}
        <replaceable>type</></literal>
        (Noah Misch)
       </para>

       <para>
        This syntax allows a standalone table to be made into a typed table,
        or a typed table to be made standalone.
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for more object types in <command>ALTER ... SET
        SCHEMA</> commands (Dimitri Fontaine)
       </para>

       <para>
        This command is now supported for conversions, operators, operator
        classes, operator families, text search configurations, text search
        dictionaries, text search parsers, and text search templates.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="SQL-CREATETABLE"><command>CREATE/ALTER TABLE</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Add <command>ALTER TABLE ...
        ADD UNIQUE/PRIMARY KEY USING INDEX</command>
        (Gurjeet Singh)
       </para>

       <para>
        This allows a primary key or unique constraint to be defined using an
        existing unique index, including a concurrently created unique index.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <command>ALTER TABLE</>
        to add foreign keys without validation (Simon Riggs)
       </para>

       <para>
        The new option is called <literal>NOT VALID</>, which can
        later be modified to <literal>VALIDATED</> and validation
        checks performed. Together these allow you to add a foreign key
        with minimal impact on read and write operations.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="SQL-ALTERTABLE"><command>ALTER TABLE
        ... SET DATA TYPE</command></link> to avoid table rewrites in
        appropriate cases (Noah Misch, Robert Haas)
       </para>

       <para>
        For example, converting a <type>varchar</> column to
        <type>text</> no longer requires a rewrite of the table.
        However, increasing the length constraint on a
        <type>varchar</> column still requires a table rewrite.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="SQL-CREATETABLE"><command>CREATE TABLE IF
        NOT EXISTS</></link> syntax (Robert Haas)
       </para>

       <para>
        This allows table creation without causing an error if the
        table already exists.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix possible <quote>tuple concurrently updated</quote> error
        when two backends attempted to add an inheritance
        child to the same table at the same time (Robert Haas)
       </para>

       <para>
        <link linkend="sql-altertable"><command>ALTER TABLE</command></link>
        now takes a stronger lock on the parent table, so that both children do
        not try to update it simultaneously.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Object Permissions</title>

     <itemizedlist>

      <listitem>
       <para>
        Add a <link linkend="SQL-SECURITY-LABEL"><command>SECURITY
        LABEL</></link> command (KaiGai Kohei)
       </para>

       <para>
        This allows security labels to be assigned to objects.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Utility Operations</title>

    <itemizedlist>

     <listitem>
      <para>
       Add transaction-level <link linkend="advisory-locks">advisory
       locks</link> (Marko Tiikkaja)
      </para>

      <para>
       This is similar to the existing session-level advisory locks,
       but the locks are automatically released at transaction end.
      </para>
     </listitem>

     <listitem>
      <para>
       Make <link linkend="SQL-TRUNCATE"><command>TRUNCATE ... RESTART
       IDENTITY</></link> restart sequences transactionally (Steve
       Singer)
      </para>

      <para>
       Previously the counter could have been left out of sync if a
       backend crashed between the on-commit truncation activity and
       commit completion.
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="SQL-COPY"><command>COPY</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Add <literal>ENCODING</> option to <link
        linkend="SQL-COPY"><command>COPY TO/FROM</></link> (Hitoshi
        Harada, Itagaki Takahiro)
       </para>

       <para>
        This allows the encoding of the <command>COPY</> file to be
        specified separately from client encoding.
       </para>
      </listitem>

      <listitem>
       <para>
        Add bidirectional <link linkend="SQL-COPY"><command>COPY</></link>
        protocol support (Fujii Masao)
       </para>

       <para>
        This is currently only used by streaming replication.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="SQL-EXPLAIN"><command>EXPLAIN</></link></title>

      <itemizedlist>

      <listitem>
       <para>
        Make <command>EXPLAIN VERBOSE</> show the function call expression
        in a <literal>FunctionScan</literal> node (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="SQL-VACUUM"><command>VACUUM</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Add additional details to the output of <link
        linkend="SQL-VACUUM"><command>VACUUM FULL VERBOSE</></link>
        and <link linkend="SQL-CLUSTER"><command>CLUSTER VERBOSE</></link>
        (Itagaki Takahiro)
       </para>

       <para>
        New information includes the live and dead tuple count and
        whether <command>CLUSTER</> is using an index to rebuild.
       </para>
      </listitem>

      <listitem>
       <para>
        Prevent <link linkend="autovacuum">autovacuum</link> from
        waiting if it cannot acquire a lock (Robert Haas)
       </para>

       <para>
        It will try to vacuum later.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="SQL-CLUSTER"><command>CLUSTER</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Allow <command>CLUSTER</> to sort the table rather than scanning
        the index when it seems likely to be cheaper (Leonardo Francalanci)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Indexes</title>

     <itemizedlist>

      <listitem>
       <para>
        Add nearest-neighbor (order-by-operator) searching to <link
        linkend="GiST"><acronym>GiST</> indexes</link> (Teodor Sigaev, Tom Lane)
       </para>

       <para>
        This allows <acronym>GiST</> indexes to quickly return the
        <replaceable>N</> closest values in a query with <literal>LIMIT</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="GIN"><acronym>GIN</> indexes</link> to index null
        and empty values (Tom Lane)
       </para>

       <para>
        This allows full <acronym>GIN</> index scans, and fixes various
        corner cases in which GIN scans would fail.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="GIN"><acronym>GIN</> indexes</link> to
        better recognize duplicate search entries (Tom Lane)
       </para>

       <para>
        This reduces the cost of index scans, especially in cases where
        it avoids unnecessary full index scans.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix <link linkend="GiST"><acronym>GiST</> indexes</link> to be fully
        crash-safe (Heikki Linnakangas)
       </para>

       <para>
        Previously there were rare cases where a <command>REINDEX</>
        would be required (you would be informed).
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Data Types</title>

    <itemizedlist>

     <listitem>
      <para>
       Allow <type>numeric</> to use a more compact, two-byte header
       in common cases (Robert Haas)
      </para>

      <para>
       Previously all <type>numeric</> values had four-byte headers;
       this saves on disk storage.
      </para>
     </listitem>

     <listitem>
      <para>
        Add support for dividing <type>money</> by <type>money</>
        (Andy Balholm)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow binary I/O on type <type>void</type> (Radoslaw Smogura)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve hypotenuse calculations for geometric operators (Paul Matthews)
      </para>

      <para>
       This avoids unnecessary overflows, and may also be more accurate.
      </para>
     </listitem>

     <listitem>
      <para>
       Support hashing array values (Tom Lane)
      </para>

      <para>
       This provides additional query optimization possibilities.
      </para>
     </listitem>

     <listitem>
      <para>
       Don't treat a composite type as sortable unless all its column types
       are sortable (Tom Lane)
      </para>

      <para>
       This avoids possible <quote>could not identify a comparison function</>
       failures at runtime, if it is possible to implement the query without
       sorting.  Also, <command>ANALYZE</> won't try to use inappropriate
       statistics-gathering methods for columns of such composite types.
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title>Casting</title>

     <itemizedlist>

     <listitem>
      <para>
        Add support for casting between <type>money</> and <type>numeric</>
        (Andy Balholm)
      </para>
     </listitem>

     <listitem>
      <para>
       Add support for casting from <type>int4</> and <type>int8</>
       to <type>numeric</> (Joey Adams)
      </para>
     </listitem>

      <listitem>
       <para>
        Allow casting a table's row type to the table's supertype if
        it's a typed table (Peter Eisentraut)
       </para>

       <para>
        This is analogous to the existing facility that allows casting a row
        type to a supertable's row type.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="functions-xml"><acronym>XML</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Add <acronym>XML</> function <link
        linkend="xml-exists"><literal>XMLEXISTS</></link> and <link
        linkend="xml-exists"><function>xpath_exists()</></link>
        functions (Mike Fowler)
       </para>

       <para>
        These are used for XPath matching.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <acronym>XML</> functions <link
        linkend="xml-is-well-formed"><function>xml_is_well_formed()</></link>,
        <link
        linkend="xml-is-well-formed"><function>xml_is_well_formed_document()</></link>,
        <link
        linkend="xml-is-well-formed"><function>xml_is_well_formed_content()</></link>
        (Mike Fowler)
       </para>

       <para>
        These check whether the input is properly-formed <acronym>XML</>.
        They provide functionality that was previously available only in
        the deprecated <filename>contrib/xml2</filename> module.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Functions</title>

     <itemizedlist>

      <listitem>
       <para>
        Add SQL function <link
        linkend="format"><function>format(text)</></link>, which
        behaves like C's <function>printf()</> (Pavel Stehule, Robert
        Haas)
       </para>

       <para>
        It currently supports formats for strings, SQL literals, and
        SQL identifiers.
       </para>
      </listitem>

      <listitem>
       <para>
        Add string functions <link
        linkend="functions-string-other"><function>concat()</></link>,
        <link
        linkend="functions-string-other"><function>concat_ws()</></link>,
        <link linkend="functions-string-other"><function>left()</></link>,
        <link linkend="functions-string-other"><function>right()</></link>,
        and <link
        linkend="functions-string-other"><function>reverse()</></link>
        (Pavel Stehule)
       </para>

       <para>
        These improve compatibility with other database products.
       </para>
      </listitem>

      <listitem>
       <para>
         Add function <link
         linkend="functions-admin-genfile"><function>pg_read_binary_file()</></link>
         to read binary files (Dimitri Fontaine, Itagaki Takahiro)
       </para>
      </listitem>

      <listitem>
       <para>
         Add a single-parameter version of function <link
         linkend="functions-admin-genfile"><function>pg_read_file()</></link>
         to read an entire file (Dimitri Fontaine, Itagaki Takahiro)
       </para>
      </listitem>

      <listitem>
       <para>
         Add three-parameter forms of <link
         linkend="array-functions-table"><function>array_to_string()</></link>
         and <link
         linkend="array-functions-table"><function>string_to_array()</></link>
         for null value processing control (Pavel Stehule)
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Object Information Functions</title>

     <itemizedlist>

      <listitem>
       <para>
        Add the <link
        linkend="functions-info-catalog-table"><function>pg_describe_object()</></link>
        function (Alvaro Herrera)
       </para>

       <para>
        This function is used to obtain a human-readable string describing
        an object, based on the <link
        linkend="catalog-pg-class"><structname>pg_class</structname></link>
        OID, object OID, and sub-object ID.  It can be used to help
        interpret the contents of <link
        linkend="catalog-pg-depend"><structname>pg_depend</structname></link>.
       </para>
      </listitem>

      <listitem>
       <para>
         Update comments for built-in operators and their underlying
         functions (Tom Lane)
       </para>

       <para>
        Functions that are meant to be used via an associated operator
        are now commented as such.
       </para>
      </listitem>

      <listitem>
       <para>
        Add variable <link
        linkend="guc-quote-all-identifiers"><varname>quote_all_identifiers</></link>
        to force the quoting of all identifiers in <command>EXPLAIN</>
        and in system catalog functions like <link
        linkend="functions-info-catalog-table"><function>pg_get_viewdef()</></link>
        (Robert Haas)
       </para>

       <para>
        This makes exporting schemas to tools and other databases with
        different quoting rules easier.
       </para>
      </listitem>

      <listitem>
       <para>
        Add columns to the <link
        linkend="infoschema-sequences"><structname>information_schema.sequences</></link>
        system view (Peter Eisentraut)
       </para>

       <para>
        Previously, though the view existed, the columns about the
        sequence parameters were unimplemented.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <literal>public</> as a pseudo-role name in <link
        linkend="functions-info-access-table"><function>has_table_privilege()</></link>
        and related functions (Alvaro Herrera)
       </para>

       <para>
        This allows checking for public permissions.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Function and Trigger Creation</title>

     <itemizedlist>

      <listitem>
       <para>
        Support <link linkend="SQL-CREATETRIGGER"><literal>INSTEAD
        OF</></link> triggers on views (Dean Rasheed)
       </para>

       <para>
        This feature can be used to implement fully updatable views.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Server-Side Languages</title>

    <sect4>
     <title><link linkend="plpgsql">PL/pgSQL</link> Server-Side Language</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="plpgsql-foreach-array"><command>FOREACH IN
        ARRAY</></link> to <link linkend="plpgsql">PL/pgSQL</link>
        (Pavel Stehule)
       </para>

       <para>
        This is more efficient and readable than previous methods of
        iterating through the elements of an array value.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <command>RAISE</command> without parameters to be caught in
        the same places that could catch a <command>RAISE ERROR</command>
        from the same location (Piyush Newe)
       </para>

       <para>
        The previous coding threw the error
        from the block containing the active exception handler.
        The new behavior is more consistent with other DBMS products.
       </para>
      </listitem>

    </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="plperl">PL/Perl</link> Server-Side Language</title>

     <itemizedlist>

      <listitem>
       <para>
        Allow generic record arguments to PL/Perl functions (Andrew
        Dunstan)
       </para>

       <para>
        PL/Perl functions can now be declared to accept type <type>record</>.
        The behavior is the same as for any named composite type.
       </para>
      </listitem>

      <listitem>
       <para>
        Convert PL/Perl array arguments to Perl arrays (Alexey Klyukin,
        Alex Hunsaker)
       </para>

       <para>
        String representations are still available.
       </para>
      </listitem>

      <listitem>
       <para>
        Convert PL/Perl composite-type arguments to Perl hashes
        (Alexey Klyukin, Alex Hunsaker)
       </para>

       <para>
        String representations are still available.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="plpython">PL/Python</link> Server-Side Language</title>

     <itemizedlist>

      <listitem>
       <para>
        Add table function support for PL/Python (Jan Urbanski)
       </para>

       <para>
        PL/Python can now return multiple <literal>OUT</> parameters
        and record sets.
       </para>
      </listitem>

      <listitem>
       <para>
        Add a validator to PL/Python (Jan Urbanski)
       </para>

       <para>
        This allows PL/Python functions to be syntax-checked at function
        creation time.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow exceptions for SQL queries in PL/Python (Jan Urbanski)
       </para>

       <para>
        This allows access to SQL-generated exception error codes from
        PL/Python exception blocks.
       </para>
      </listitem>

      <listitem>
       <para>
         Add PL/Python explicit subtransactions (Jan Urbanski)
       </para>
      </listitem>

      <listitem>
       <para>
        Add PL/Python functions for quoting strings (Jan Urbanski)
       </para>

       <para>
        The functions are <link
        linkend="plpython-util"><literal>plpy.quote_ident</></link>,
        <link linkend="plpython-util"><literal>plpy.quote_literal</></link>,
        and <link
        linkend="plpython-util"><literal>plpy.quote_nullable</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
         Add traceback information to PL/Python errors (Jan Urbanski)
       </para>
      </listitem>

      <listitem>
       <para>
         Report PL/Python errors from iterators with <literal>PLy_elog</> (Jan
         Urbanski)
       </para>
      </listitem>

      <listitem>
       <para>
        Fix exception handling with Python 3 (Jan Urbanski)
       </para>

       <para>
        Exception classes were previously not available in
        <literal>plpy</> under Python 3.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Client Applications</title>

    <itemizedlist>

     <listitem>
      <para>
        Mark <link
        linkend="APP-CREATELANG"><application>createlang</></link>
        and <link linkend="APP-DROPLANG"><application>droplang</></link>
        as deprecated now that they just invoke extension commands (Tom
        Lane)
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="APP-PSQL"><application>psql</></link></title>

     <itemizedlist>

      <listitem>
       <para>
         Add <application>psql</> command <literal>\conninfo</>
         to show current connection information (David Christensen)
       </para>
      </listitem>

      <listitem>
       <para>
         Add <application>psql</> command <literal>\sf</> to
         show a function's definition (Pavel Stehule)
       </para>
      </listitem>

      <listitem>
       <para>
         Add <application>psql</> command <literal>\dL</> to list
         languages (Fernando Ike)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <option>S</> (<quote>system</>) option to <application>psql</>'s
        <literal>\dn</> (list schemas) command (Tom Lane)
       </para>

       <para>
        <literal>\dn</> without <literal>S</> now suppresses system
        schemas.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <application>psql</>'s <literal>\e</> and <literal>\ef</>
        commands to accept a line number to be used to position the
        cursor in the editor (Pavel Stehule)
       </para>

       <para>
        This is passed to the editor according to the
        <envar>PSQL_EDITOR_LINENUMBER_ARG</> environment variable.
       </para>
      </listitem>

      <listitem>
       <para>
        Have <application>psql</> set the client encoding from the
        operating system locale by default (Heikki Linnakangas)
       </para>

       <para>
        This only happens if the <envar>PGCLIENTENCODING</> environment
        variable is not set.
       </para>
      </listitem>

      <listitem>
       <para>
        Make <literal>\d</literal> distinguish between unique
        indexes and unique constraints (Josh Kupershmidt)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <literal>\dt+</literal> report <function>pg_table_size</>
        instead of <function>pg_relation_size</> when talking to 9.0 or
        later servers (Bernd Helmle)
       </para>

       <para>
        This is a more useful measure of table size, but note that it is
        not identical to what was previously reported in the same display.
       </para>
      </listitem>

      <listitem>
       <para>
        Additional tab completion support (Itagaki Takahiro, Pavel Stehule,
        Andrey Popp, Christoph Berg, David Fetter, Josh Kupershmidt)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="APP-PGDUMP"><application>pg_dump</></link></title>

     <itemizedlist>

      <listitem>
       <para>
         Add <link linkend="APP-PGDUMP"><application>pg_dump</></link>
         and <link
         linkend="APP-PG-DUMPALL"><application>pg_dumpall</></link>
         option <option>--quote-all-identifiers</> to force quoting
         of all identifiers (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <literal>directory</> format to <application>pg_dump</>
        (Joachim Wieland, Heikki Linnakangas)
       </para>

       <para>
        This is internally similar to the <literal>tar</>
        <application>pg_dump</> format.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="APP-PG-CTL"><application>pg_ctl</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Fix <application>pg_ctl</>
        so it no longer incorrectly reports that the server is not
        running (Bruce Momjian)
       </para>

       <para>
        Previously this could happen if the server was running but
        <application>pg_ctl</> could not authenticate.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve <application>pg_ctl</> start's <quote>wait</quote>
        (<option>-w</>) option (Bruce Momjian, Tom Lane)
       </para>

       <para>
        The wait mode is now significantly more robust.  It will not get
        confused by non-default postmaster port numbers, non-default
        Unix-domain socket locations, permission problems, or stale
        postmaster lock files.
       </para>
      </listitem>

      <listitem>
       <para>
         Add <literal>promote</> option to <application>pg_ctl</> to
         switch a standby server to primary (Fujii Masao)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title><application>Development Tools</></title>

    <sect4>
     <title><link linkend="libpq"><application>libpq</></link></title>

     <itemizedlist>

      <listitem>
       <para>
        Add a libpq connection option <literal>client_encoding</>
        which behaves like the <envar>PGCLIENTENCODING</> environment
        variable (Heikki Linnakangas)
       </para>

       <para>
        The value <literal>auto</> sets the client encoding based on
        the operating system locale.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link
        linkend="libpq-pqlibversion"><function>PQlibVersion()</></link>
        function which returns the libpq library version (Magnus
        Hagander)
       </para>

       <para>
        libpq already had <function>PQserverVersion()</> which returns
        the server version.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow libpq database clients to
        check the user name of the server process using <link
        linkend="libpq-connect-requirepeer"><literal>requirepeer</></link>
        when connecting via Unix-domain sockets
        (Peter Eisentraut)
       </para>

       <para>
        <productname>PostgreSQL</> already allowed servers to check
        the client user name when connecting via Unix-domain sockets.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="libpq-pqping"><function>PQping()</></link>
        and <link
        linkend="libpq-pqpingparams"><function>PQpingParams()</></link>
        to libpq (Bruce Momjian, Tom Lane)
       </para>

       <para>
        These functions allow detection of the server's status without
        trying to open a new session.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="ecpg"><application>ECPG</></link></title>

     <itemizedlist>

      <listitem>
       <para>
         Allow ECPG to accept dynamic cursor names even in
         <literal>WHERE CURRENT OF</literal> clauses
       </para>
      </listitem>

     </itemizedlist>
    </sect4>

   </sect3>

   <sect3>
    <title>Build Options</title>

     <itemizedlist>

      <listitem>
       <para>
        Use <literal>+Olibmerrno</> compile flag with HP-UX C compilers
        that accept it (Ibrar Ahmed)
       </para>

       <para>
        This avoids possible misbehavior of math library calls on recent
        HP platforms.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Makefiles</title>

     <itemizedlist>

      <listitem>
       <para>
        Improved parallel make support (Peter Eisentraut)
       </para>

       <para>
        This allows for faster compiles.  Also, <literal>make -k</>
        now works more consistently.
       </para>
      </listitem>

      <listitem>
       <para>
         Require <acronym>GNU</> <link
         linkend="install-requirements"><application>make</></link>
         3.80 or newer (Peter Eisentraut)
       </para>

       <para>
        This is necessary because of the parallel-make improvements.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <literal>make maintainer-check</> target
        (Peter Eisentraut)
       </para>

       <para>
        This target performs various source code checks that are not
        appropriate for either the build or the regression tests.  Currently:
        duplicate_oids, SGML syntax and tabs check, NLS syntax check.
       </para>
      </listitem>

      <listitem>
       <para>
        Support <literal>make check</> in <filename>contrib</>
        (Peter Eisentraut)
       </para>

       <para>
        Formerly only <literal>make installcheck</> worked, but now
        there is support for testing in a temporary installation.
        The top-level <literal>make check-world</> target now includes
        testing <filename>contrib</> this way.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Windows</title>

     <itemizedlist>

      <listitem>
       <para>
         On Windows, allow <link
         linkend="app-pg-ctl"><application>pg_ctl</></link> to register
         the service as auto-start or start-on-demand (Quan Zongliang)
       </para>
      </listitem>

      <listitem>
       <para>
        Add support for collecting <link linkend="windows-crash-dumps">crash
        dumps</link> on Windows (Craig Ringer, Magnus Hagander)
       </para>

       <para>
        <productname>minidumps</> can now be generated by non-debug
        Windows binaries and analyzed by standard debugging tools.
       </para>
      </listitem>

      <listitem>
       <para>
        Enable building with the MinGW64 compiler (Andrew Dunstan)
       </para>

       <para>
        This allows building 64-bit Windows binaries even on non-Windows
        platforms via cross-compiling.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Source Code</title>

     <itemizedlist>

      <listitem>
       <para>
        Revise the API for GUC variable assign hooks (Tom Lane)
       </para>

       <para>
        The previous functions of assign hooks are now split between check
        hooks and assign hooks, where the former can fail but the latter
        shouldn't.  This change will impact add-on modules that define custom
        GUC parameters.
       </para>
      </listitem>

      <listitem>
       <para>
         Add latches to the source code to wait for events (Heikki
         Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
         Centralize data modification permissions-checking logic
         (KaiGai Kohei)
       </para>
      </listitem>

      <listitem>
       <para>
         Add missing <function>get_<replaceable>object</>_oid()</function> functions, for consistency
         (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
         Improve ability to use C++ compilers for <link
         linkend="xfunc-c">compiling add-on modules</link> by removing
         conflicting key words (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
         Add support for DragonFly <acronym>BSD</> (Rumko)
       </para>
      </listitem>

      <listitem>
       <para>
         Expose <function>quote_literal_cstr()</> for backend use
         (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Run <link linkend="build">regression tests</link> in the
        default encoding (Peter Eisentraut)
       </para>

       <para>
        Regression tests were previously always run with
        <literal>SQL_ASCII</> encoding.
       </para>
      </listitem>

      <listitem>
       <para>
         Add <application>src/tools/git_changelog</> to replace
         <application>cvs2cl</> and <application>pgcvslog</> (Robert
         Haas, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <application>git-external-diff</> script to
        <filename>src/tools</> (Bruce Momjian)
       </para>

       <para>
        This is used to generate context diffs from git.
       </para>
      </listitem>

      <listitem>
       <para>
         Improve support for building with
         <application>Clang</application> (Peter Eisentraut)
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Server Hooks</title>

     <itemizedlist>

      <listitem>
       <para>
         Add source code hooks to check permissions (Robert Haas,
         Stephen Frost)
       </para>
      </listitem>

      <listitem>
       <para>
         Add post-object-creation function hooks for use by security
         frameworks (KaiGai Kohei)
       </para>
      </listitem>

      <listitem>
       <para>
         Add a client authentication hook (KaiGai Kohei)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Contrib</title>

    <itemizedlist>

     <listitem>
      <para>
       Modify <filename>contrib</> modules and stored procedure
       languages to install via the new <link
       linkend="extend-extensions">extension</link> mechanism (Tom Lane,
       Dimitri Fontaine)
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="file-fdw"><filename>contrib/file_fdw</></link>
       foreign-data wrapper (Shigeru Hanada)
      </para>

      <para>
       Foreign tables using this foreign data wrapper can read flat files
       in a manner very similar to <command>COPY</>.
      </para>
     </listitem>

     <listitem>
      <para>
        Add nearest-neighbor support to <link
        linkend="pgtrgm"><filename>contrib/pg_trgm</></link> and <link
        linkend="btree-gist"><filename>contrib/btree_gist</></link>
        (Teodor Sigaev)
      </para>
     </listitem>

     <listitem>
      <para>
        Add <link
        linkend="btree-gist"><filename>contrib/btree_gist</></link>
        support for searching on not-equals (Jeff Davis)
      </para>
     </listitem>

     <listitem>
      <para>
        Fix <link
        linkend="fuzzystrmatch"><filename>contrib/fuzzystrmatch</></link>'s
        <function>levenshtein()</> function to handle multibyte characters
        (Alexander Korotkov)
      </para>
     </listitem>

     <listitem>
      <para>
        Add <function>ssl_cipher()</> and <function>ssl_version()</>
        functions to <link
        linkend="sslinfo"><filename>contrib/sslinfo</></link> (Robert
        Haas)
      </para>
     </listitem>

     <listitem>
      <para>
       Fix <link linkend="intarray"><filename>contrib/intarray</></link>
       and <link linkend="hstore"><filename>contrib/hstore</></link>
       to give consistent results with indexed empty arrays (Tom Lane)
      </para>

      <para>
       Previously an empty-array query that used an index might return
       different results from one that used a sequential scan.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <link linkend="intarray"><filename>contrib/intarray</></link>
       to work properly on multidimensional arrays (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       In
       <link linkend="intarray"><filename>contrib/intarray</></link>,
       avoid errors complaining about the presence of nulls in cases where no
       nulls are actually present (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       In
       <link linkend="intarray"><filename>contrib/intarray</></link>,
       fix behavior of containment operators with respect to empty arrays
       (Tom Lane)
      </para>

      <para>
       Empty arrays are now correctly considered to be contained in any other
       array.
      </para>
     </listitem>

     <listitem>
      <para>
       Remove <link linkend="xml2"><filename>contrib/xml2</></link>'s
       arbitrary limit on the number of
       <replaceable>parameter</>=<replaceable>value</> pairs that can be
       handled by <function>xslt_process()</> (Pavel Stehule)
      </para>

      <para>
       The previous limit was 10.
      </para>
     </listitem>

     <listitem>
      <para>
       In <link linkend="pageinspect"><filename>contrib/pageinspect</></link>,
       fix heap_page_item to return infomasks as 32-bit values (Alvaro Herrera)
      </para>

      <para>
       This avoids returning negative values, which was confusing.  The
       underlying value is a 16-bit unsigned integer.
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title>Security</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="sepgsql"><filename>contrib/sepgsql</></link>
        to interface permission checks with <acronym>SE</>-Linux (KaiGai Kohei)
       </para>

       <para>
        This uses the new <link
        linkend="SQL-SECURITY-LABEL"><command>SECURITY LABEL</></link>
        facility.
       </para>
      </listitem>

      <listitem>
       <para>
        Add contrib module <link
        linkend="auth-delay"><filename>auth_delay</></link> (KaiGai
        Kohei)
       </para>

       <para>
        This causes the server to pause before returning authentication
        failure;  it is designed to make brute force password attacks
        more difficult.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="dummy-seclabel">dummy_seclabel</link>
        contrib module (KaiGai Kohei)
       </para>

       <para>
        This is used for permission regression testing.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Performance</title>

     <itemizedlist>

      <listitem>
       <para>
         Add support for <literal>LIKE</> and <literal>ILIKE</> index
         searches to <link
         linkend="pgtrgm"><filename>contrib/pg_trgm</></link> (Alexander
         Korotkov)
       </para>
      </listitem>

      <listitem>
       <para>
         Add <function>levenshtein_less_equal()</> function to <link
         linkend="fuzzystrmatch"><filename>contrib/fuzzystrmatch</></link>,
         which is optimized for small distances (Alexander Korotkov)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve performance of index lookups on <link
        linkend="seg"><filename>contrib/seg</></link> columns (Alexander
        Korotkov)
       </para>
      </listitem>

      <listitem>
       <para>
         Improve performance of <link
         linkend="pgupgrade"><application>pg_upgrade</></link> for
         databases with many relations (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
         Add flag to <link
         linkend="pgbench"><filename>contrib/pgbench</></link> to
         report per-statement latencies (Florian Pflug)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Fsync Testing</title>

     <itemizedlist>

      <listitem>
       <para>
         Move <filename>src/tools/test_fsync</> to <link
         linkend="pgtestfsync"><filename>contrib/pg_test_fsync</></link>
         (Bruce Momjian, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <literal>O_DIRECT</> support to <link
        linkend="pgtestfsync"><filename>contrib/pg_test_fsync</></link>
        (Bruce Momjian)
       </para>

       <para>
        This matches the use of <literal>O_DIRECT</> by <link
        linkend="guc-wal-sync-method"><varname>wal_sync_method</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
         Add new tests to <link
         linkend="pgtestfsync"><filename>contrib/pg_test_fsync</></link>
         (Bruce Momjian)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Documentation</title>

    <itemizedlist>

     <listitem>
      <para>
        Extensive <link linkend="ecpg"><application>ECPG</> documentation</link>
        improvements (Satoshi Nagayasu)
      </para>
     </listitem>

     <listitem>
      <para>
        Extensive proofreading and documentation improvements
        (Thom Brown, Josh Kupershmidt, Susanne Ebrecht)
      </para>
     </listitem>

     <listitem>
      <para>
       Add documentation for <link
       linkend="guc-exit-on-error"><varname>exit_on_error</></link>
       (Robert Haas)
      </para>

      <para>
       This parameter causes sessions to exit on any error.
      </para>
     </listitem>

     <listitem>
      <para>
       Add documentation for <link
       linkend="functions-info-catalog-table"><function>pg_options_to_table()</></link>
       (Josh Berkus)
      </para>

      <para>
       This function shows table storage options in a readable form.
      </para>
     </listitem>

     <listitem>
      <para>
       Document that it is possible to access all composite type
       fields using <link
       linkend="field-selection"><literal>(compositeval).*</></link>
       syntax (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Document that <link
       linkend="functions-string-other"><function>translate()</></link>
       removes characters in <literal>from</> that don't have a
       corresponding <literal>to</> character (Josh Kupershmidt)
      </para>
     </listitem>

     <listitem>
      <para>
       Merge docs for <command>CREATE CONSTRAINT TRIGGER</> and <link
       linkend="SQL-CREATETRIGGER"><command>CREATE TRIGGER</></link>
       (Alvaro Herrera)
      </para>
     </listitem>

     <listitem>
      <para>
       Centralize <link linkend="ddl-priv">permission</link> and <link
       linkend="upgrading">upgrade</link> documentation (Bruce Momjian)
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="sysvipc-parameters">kernel tuning
       documentation</link> for Solaris 10 (Josh Berkus)
      </para>

      <para>
       Previously only Solaris 9 kernel tuning was documented.
      </para>
     </listitem>

     <listitem>
      <para>
       Handle non-ASCII characters consistently in <filename>HISTORY</> file
       (Peter Eisentraut)
      </para>

      <para>
       While the <filename>HISTORY</> file is in English, we do have to deal
       with non-ASCII letters in contributor names.  These are now
       transliterated so that they are reasonably legible without assumptions
       about character set.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

  </sect2>
 </sect1>
