<!-- doc/src/sgml/release-9.1.sgml -->

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

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

  <sect2>
   <title>Overview</title>

   <para>
    This release of
    <productname>PostgreSQL</> adds ...  Major enhancements include:
   </para>

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

   <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 ...
    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>
       This 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 the proper way to embed escapes in strings and is
       unaffected by this change.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Casting</title>

    <itemizedlist>

     <listitem>
      <para>
       Disallow functional or attribute string data type casts for
       composite types (Tom Lane)
      </para>

      <para>
       For example, disallow composite_name.text and text(composite_name).
       <literal>CAST</> and <literal>::</> are still available for
       casting.
      </para>
     </listitem>

     <listitem>
      <para>
       Tighten casting checks for domains based on arrays (Tom Lane)
      </para>
    
      <para>
       **Details?
      </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 <literal>NULL</>.
      </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 <literal>NULL</>.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
      <para>
       Fix improper checks for before/after triggers (Tom Lane)
      </para>
     
      <para>
       **Tom, I need more details on the impact of this for existing
       installs.
      </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 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 reporting code to be consistent
       with SQL error line reporting (Pavel Stehule)
      </para>
     
      <para>
       Previously error numbering was off by one.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
      <para>
       Have <link
       linkend="monitoring-stats-funcs-table"><function>pg_stat_reset()</></link>
       reset all database-level statistics (Tom Lane)
      </para>

      <para>
       Some 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, current as of 2011-03-15</title>
    <para>
     Version 9.1 has ...
    </para>

   <sect3>
    <title>Server</title>

    <sect4>
     <title>Performance</title>

     <itemizedlist>

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

       <para>
        These tables are optimized for performance but are cleared in
        case of a server crash.
       </para>
      </listitem>

      <listitem>
       <para>
        Support <literal>RIGHT</> and <literal>FULL OUTER JOIN</> in
        hash joins (Tom Lane)
       </para>

       <para>
        Previously hash joins could not be considered for outer joins;
        this provides additional query optimization possibilities.
        **What about <literal>LEFT</> joins?
       </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 commit_siblings with less overhead.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Optimizer</title>

     <itemizedlist>

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

       <para>
        This allows optimization of <literal>ORDER BY</> and
        <literal>LIMIT</> clauses in inheritance table queries.
       </para>
      </listitem>

      <listitem>
       <para>
         Allow optimizations of <literal>MIN</>/<literal>MAX</> for
         inheritance table queries (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow hash joins for array values (Tom Lane)
       </para>

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

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

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Authentication</title>

     <itemizedlist>

      <listitem>
       <para>
        Support host names and host suffixes (e.g. .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 keyword <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>
        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 <acronym>SSPI</> authenticate to Windows servers.
       </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 client_hostname field 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>
        statistic 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 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>
        Cancelations can occur because of dropped tablespaces, lock
        timeouts, old snapshots, pinned buffers, and deadlocks.
       </para>
      </listitem>

      <listitem>
       <para>
        Add a <literal>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>
         Add record of last reset in database and background writer-level
         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 buffers_backend_fsync field to <link
        linkend="monitoring-stats-views-table"><structname>pg_stat_bgwriter</></link>
        (Greg Smith)
       </para>

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

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

       <para>
        This is designed for cluster managers that want to control
        restarts.
       </para>
      </listitem>

      </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Streaming Replication and Continuous Archiving</title>

    <itemizedlist>

     <listitem>
      <para>
       Add a <link
       linkend="guc-synchronous-replication"><varname>synchronous_replication</></link>
       option (Simon Riggs, Fujii Masao)
      </para>

      <para>
       This allows the primary to wait for the standby to receive
       transaction information before acknowledging the commit.
      </para>
     </listitem>

     <listitem>
      <para>
       Add variable <link
       linkend="guc-hot-standby-feedback"><varname>hot_standby_feedback</></link>
       to enable standbys to communicate their needed snapshots to
       the primary (Simon Riggs)
      </para>

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

     <listitem>
      <para>
       Add 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 creating a standby server.
      </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
       and allows non-superusers to initiate replication connections.
       Previously only superusers could initiate replication
       connections;  superusers have this permission by default.
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title>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 on the primary that generated the most
        recent commit or abort record applied on the standby.
       </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 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 in <filename>recovery.conf</>.
       </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 if the
        recovery point is the one desired.
       </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>
        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>
        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>
        This allows <command>INSERT</>/<command>UPDATE</>/<command>DELETE</>
        <literal>RETURNING</> in <literal>WITH</> clauses to pass rows
        to outer queries.
       </para>
      </listitem>

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

       <para>
        Specifically, let <command>SELECT</> query results be fed
        into <command>INSERT</>, <command>UPDATE</>, <command>DELETE</>
        statements.
       </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 the use of the keyword <link
        linkend="queries-union"><literal>DISTINCT</></link> in
        <literal>UNION</>/<literal>INTERSECT</>/<literal>EXCEPT</>
        clauses (Tom Lane)
       </para>

       <para>
        <literal>DISTINCT</> is the default behavior so use of this
        keyword is redundant.
       </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 the database level.
        Collation can now be set per column, domain, index, or
        expression.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

     <itemizedlist>

      <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 in foreign sources to be used like
        native <productname>PostgreSQL</>-stored data.
       </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>
        Add support for more object types in <command>ALTER ... SET
        SCHEMA</> commands (Dimitri Fontaine)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="SQL-ALTERTABLE"><command>ALTER TABLE ...
        ADD UNIQUE</></link>/<literal>PRIMARY KEY USING INDEX</>
        (Gurjeet Singh)
       </para>

       <para>
        This allows existing unique indexes to be used as primary
        keys, including indexes that were created concurrently.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="SQL-ALTERTABLE"><command>ALTER TABLE</></link>
        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.
       </para>
      </listitem>

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

       <para>
        For example, converting a varchar column to text no longer
        requires a rewrite of the table.  **Length changes require
        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>

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

      <para>
       Previously asking for serializable isolation produced
       snapshot isolation, which had certain documented anomalies.
       The old snapshot isolation level is still accessible by
       requesting the <link linkend="xact-repeatable-read"><literal>REPEATABLE
       READ</></link> isolation level.
      </para>
     </listitem>

     <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 are freed 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>
         Have <command>EXPLAIN VERBOSE</>
         show the function call expression (Tom Lane)
       </para>
      </listitem>

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

       <para>
        Previously <command>EXPLAIN ANALYZE</> used a slightly different
        snapshot for queries involving rules.
       </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>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
        <literal>LIMIT</>-specified closest values.
       </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.
       </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 many 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>

    </itemizedlist>

    <sect4>
     <title>Casting</title>

     <itemizedlist>

     <listitem>
      <para>
        Add support for casting between <type>money</> and <type>numeric</>
        (Andy Balholm)
      </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>
        **Needs description.
       </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>
        This is 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</>.
       </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>
        **Why were these added?
       </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 <literal>NULL</> 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 comments on objects.  **Alvaro,
        why is this useful for pg_depend?
       </para>
      </listitem>

      <listitem>
       <para>
         Update comments for built-in operators and their underlying
         functions (Tom Lane)
       </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 fields to the <link
        linkend="infoschema-sequences"><structname>information_schema.sequences</></link>
        system view (Peter Eisentraut)
       </para>

       <para>
        Previously, though the view existed, all of these view fields
        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>

      <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>Function and Trigger Creation</title>

     <itemizedlist>

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

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

      <listitem>
       <para>
        Reduce lock levels for <link
        linkend="SQL-CREATETRIGGER"><command>CREATE TRIGGER</></link>
        and some <link linkend="SQL-ALTERTABLE"><command>ALTER
        TABLE</></link> and <link linkend="SQL-CREATERULE"><command>CREATE
        RULE</></link> operations (Simon Riggs)
       </para>

       <para>
        This improves concurrency.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

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

      <para>
       This is more efficient than previous methods.
      </para>
     </listitem>

    </itemizedlist>

    <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>
        **Andrew, I need details on this.
       </para>
      </listitem>

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

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

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

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

       <para>
        This allows PL/Python functions to be validated 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>
        Allow PL/Python to access <literal>SQLSTATE</> exception values
        (Jan Urbanski)
       </para>

       <para>
        **Is this the same as the item above?
       </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>
         Report PL/Python errors from iterators with <literal>PLy_elog</> (Jan
         Urbanski)
       </para>
      </listitem>

      <listitem>
       <para>
        Overhaul of PL/Python (Jan Urbanski)
       </para>

       <para>
        This includes exception support for Python 3.  **More?
       </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 use the extension framework (Tom
        Lane)
      </para>
     </listitem>

    </itemizedlist>

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

     <itemizedlist>

      <listitem>
       <para>
         Add the <literal>\conninfo</> command to <application>psql</>,
         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 system table <option>S</> option to <application>psql</>
        <literal>\dn</> (schemas) (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 using the
        <envar>EDITOR_LINENUMBER_SWITCH</> 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>
         Additional tab completion of <application>psql</> variables (Pavel
         Stehule)
       </para>
      </listitem>

      <listitem>
       <para>
         More <application>psql</> tab completion support (Itagaki
         Takahiro)
       </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 "wait" (<option>-w</>) mode to handle non-standard
        port numbers, non-standard unix-domain socket locations,
        permission problems, and stale postmaster lock files (Bruce
        Momjian)
       </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 use Unix-domain sockets to
        check the user name of the server process using <link
        linkend="libpq-connect-requirepeer"><literal>requirepeer</></link>
        (Peter Eisentraut)
       </para>

       <para>
        <productname>PostgreSQL</> already allowed servers to determine
        the client user name 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>
        The allow detection of the server's status without creating
        a new session.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="extension">extensions</link> which allow
        packaged additions to <productname>PostgreSQL</> (Dimitri
        Fontaine, Tom Lane)
       </para>

       <para>
        This is 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>
        command;  this replaces a more manual method of adding features
        to <productname>PostgreSQL</>.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Makefiles</title>

     <itemizedlist>

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

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

       <para>
        This allows for faster compiles.  Also, make <option>-k</>
        and make <option>-q</> now work properly.  **When was recursive
        make supported?
       </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 with cross-compiling.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

     <itemizedlist>

      <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 get_{object}_oid() functions, for consistency
         (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
         Improve ability to use C++ compilers for <link
         linkend="xfunc-c">backend compiles</link> by removing
         conflicting keywords (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>

     </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="extension">extension</link> mechanism (Tom Lane,
       Dimitri Fontaine)
      </para>

      <para>
       This replaces a more manual method of installation.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="file-fdw"><filename>contrib/file_fdw</></link>
       foreign-data wrapper for reading files via <command>COPY
       </>(Shigeru Hanada)
      </para>

      <para>
       This adds foreign table support for flat-file.
      </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>
        Allow <link
        linkend="fuzzystrmatch"><filename>contrib/fuzzystrmatch</></link>'s
        <function>levenshtein()</> function handle multi-byte 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>
       In <link linkend="xml2"><filename>contrib/xml2</></link>, remove
       arbitrary limit on the number of parameter=value pairs that
       can be handled by <function>xslt_process()</> (Pavel Stehule)
      </para>

      <para>
       The previous limit was 20.
      </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>

       <para>
        **Confirm this does not affect <application>pg_upgrade</>
       </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>
       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 parameter shows table storage options.
      </para>
     </listitem>

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

      <para>
       **Is this syntax new in 9.1?
      </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>

    </itemizedlist>

   </sect3>

  </sect2>
 </sect1>



<!-- This is (hopefully) up-to-date with commits through 2011-03-08 -->


 <sect1 id="release-9-1-alpha">
  <title>Release 9.1alpha4</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>
    <para>
      These notes are cumulative over all alpha releases of the current
      development cycle.  Items that are new in the latest alpha release are
      <emphasis>emphasized</emphasis>.
    </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>Testing</title>
    <para>
      The primary reason we release alphas is to get users to test new
      features as early as possible.  If you are interested in helping
      with organized testing, please see
      <ulink url="http://wiki.postgresql.org/wiki/HowToBetaTest">the
      testing information page</ulink>.
      </para>
  </sect2>
  <sect2>
    <title>Changes</title>

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

       <listitem>
        <para>
         <emphasis>Support named restore points</emphasis>
        </para>
        <para>
         Named restore points can be created using a new server function,
         pg_create_restore_point.  A new recovery.conf parameter,
         recovery_target_name, allows recovery to stop at a named restore
         point.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add new <filename>recovery.conf</> parameter, pause_at_recovery_target,
         which defaults to on</emphasis>
        </para>
        <para>
         This is a behavior change from previous releases, which entered normal
         running upon reaching the recovery target.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add pg_is_xlog_replay_paused, pg_xlog_replay_pause, and
         pg_xlog_replay_resume functions</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow standby servers to send information on running
         transactions back to the master</emphasis>
        </para>
        <para>
         When enabled, this prevents most recovery conflicts on the slave,
         but may cause MVCC bloat on the master.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Support streaming base backups</emphasis>
        </para>
        <para>
         A new client, pg_basebackup, can be used to perform a streaming base
         backup.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Synchronous replication</emphasis>
        </para>
        <para>
         When enabled, transaction commit will wait for WAL records to be
         replicated before informing the client that a transaction has
         successfully committed.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>When recovery_target_timeline='latest', periodically
         rescan the archive for new timelines</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>

    <sect3>
      <title>SQL Features</title>
      <itemizedlist>

       <listitem>
        <para>
         Add ALTER ... SET SCHEMA support for conversions,
         operators, operator classes, operator families, text search
         configurations, text search dictionaries, text search
         parsers, and text search templates
        </para>
       </listitem>

       <listitem>
        <para>
         Make TRUNCATE ... RESTART IDENTITY restart sequences transactionally
        </para>

        <para>
         Previously, the sequence restart did not roll back on error.
         This meant that an error between truncating and committing
         left the sequences out of sync with the table contents, with
         potentially bad consequences as were noted in a Warning on
         the TRUNCATE man page.
        </para>
       </listitem>

       <listitem>
        <para>
         Prevent invoking I/O conversion casts via
         functional/attribute notation
        </para>
        <para>
         This was found to be confusing in some cases.  The
         functionality is still available via cast syntax.
        </para>
       </listitem>

       <listitem>
        <para>
         Add ALTER TYPE ... ADD/DROP/ALTER/RENAME ATTRIBUTE
        </para>
       </listitem>

       <listitem>
        <para>
         Support triggers on views
        </para>

        <para>
         This adds the SQL-standard concept of an INSTEAD OF trigger,
         which is fired instead of performing a physical
         insert/update/delete.  The trigger function is passed the
         entire old and/or new rows of the view, and must figure out
         what to do to the underlying tables to implement the update.
         So this feature can be used to implement updatable views
         using trigger programming style rather than rule hacking.
         </para>
       </listitem>

       <listitem>
        <para>
         Allow WITH clauses to be attached to INSERT, UPDATE, DELETE
         statements
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow INSERT/UPDATE/DELETE to be used inside a WITH
         clause</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         Allow new values to be added to an existing enum type
        </para>
       </listitem>

       <listitem>
        <para>
         Recognize functional dependency on primary
         keys
        </para>
        <para>
         This allows a table's other columns to be referenced without listing
         them in GROUP BY, so long as the primary key column(s) are listed in
         GROUP BY.
        </para>
       </listitem>

       <listitem>
        <para>
         Add CREATE TABLE IF NOT EXISTS
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow a table's row type to be cast to the table's supertype
         if it's a type table</emphasis>
        </para>
        <para>
         This is analagous to the existing facility that allows casting a row
         type to a supertable's row type.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Make foreign data wrappers functional, and support FOREIGN
         TABLEs</emphasis>
        </para>
        <para>
         Foreign tables are component of SQL/MED, and provide a framework to
         allow data stored outside the database to be accessed via SQL.
         contrib/file_fdw is provided as a sample foreign data wrapper.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow a unique or primary key constraint to be created
         using an existing index</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Implement Serializable Snapshot Isolation, in order to
         provide a more robust serializable transaction mode</emphasis>
        </para>
        <para>
         In previous releases, the REPEATABLE READ and SERIALIZABLE isolation
         levels were identical.  The historical behavior of REPEATABLE READ is
         unchanged in this release, but SERIALIZABLE now provides stronger
         guarantees.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow foreign key constraints to be added as initially
         NOT VALID, and validated later</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow multiple collations to be used within a single
         database</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Support extensions, which provide a cleaner method for
         installing and upgrading add-on modules, such as those in contrib
         </emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Teach ALTER TABLE ... SET DATA TYPE to avoid a table write
         in some cases where it isn't necessary
         </emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add ENCODING option to COPY TO/FROM</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow binary I/O of type "void"</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Rearrange snapshot handlling to make rule expansion more
         consistent</emphasis>
        </para>
        <para>
         Portals, SQL functions, and SPI all now agree that a completely new
         MVCC snapshot should be obtained only after fully executing each
         original query.  This is equivalent to the prior behavior of EXPLAIN
         ANALYZE.  It eliminates one source of concurrency hazards for
         rules, and should also be marginally faster.
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Performance</title>
      <itemizedlist>

       <listitem>
        <para>
         Optimize the commit_siblings configuration parameter
        </para>
       </listitem>

       <listitem>
        <para>
         KNN GiST, otherwise known as order-by-operator support for GiST
        </para>

        <para>
         This can be used to optimize nearest-neighbor searches.
        </para>
       </listitem>

       <listitem>
        <para>
         Improve process shutdown speed
        </para>
       </listitem>

       <listitem>
        <para>
         Speed up conversion of signed integers to C strings
        </para>
       </listitem>

       <listitem>
        <para>
         Support MergeAppend plans, to allow sorted output
         from append relations
        </para>

        <para>
         This eliminates the former need to sort the output of an
         Append scan when an ordered scan of an inheritance tree is
         wanted.  This should be particularly useful for fast-start
         cases such as queries with LIMIT.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Support unlogged tables</emphasis>
        </para>
        <para>
         The contents of an unlogged table are not WAL-logged; thus, they
         are not replicated and are truncated whenever the database system
         enters recovery.  Indexes on unlogged tables are also unlogged, but
         GIST indexes on unlogged tables are not currently supported.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Hash joins now support right and full outer joins</emphasis>
        </para>
        <para>
         Previously, full joins could be implemented only as a merge join,
         and left and right outer joins could only hash the table on the
         nullable side of the join.  This optimization is particularly
         advantageous when the non-nullable side of a left or right outer
         join is much smaller than the nullable side.
        </para>
       </listitem>

       <listitem>
        <para>
         Reduce the memory requirement for large ispell dictionaries
        </para>
       </listitem>

       <listitem>
        <para>
         Teach CLUSTER to use seqscan-and-sort when it's faster than
         indexscan
        </para>
       </listitem>

       <listitem>
        <para>
         Improve GIN indexscan cost estimation
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Fix GIN to support null keys, empty and null items, and
         full index scans</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Teach GIN to combine duplicate keys even across different
         quals</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         Performance improvements in pg_upgrade for uses with many tables
        </para>
       </listitem>

       <listitem>
        <para>
         Reduce lock levels of CREATE TRIGGER and some ALTER
         TABLE, CREATE RULE actions
        </para>
       </listitem>

       <listitem>
        <para>
         Add some knowledge about prefix matches to
         tsmatchsel()
        </para>
       </listitem>

       <listitem>
        <para>
         Replace the naive HYPOT() macro with a
         standards-conformant hypotenuse function
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Avoid unnecessary detoast when comparing unequal-length text
         or bytea values for equality or inequality</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Try to compact the background writer's fsync queue when
         it overflows, instead of doing an fsync per block written</emphasis>
        </para>
       </listitem>

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

       <listitem>
        <para>
         Change the default value of
         <literal>standard_conforming_strings</> to
         <literal>on</>
        </para>
        <warning>
         <para>
          This is a significant incompatibility with previous releases,
          because it may break unwary applications in security-critical ways.
         </para>
        </warning>
       </listitem>

       <listitem>
        <para>
         Add <literal>log_file_mode</> parameter
        </para>
        <para>
         This allows control of the file permissions set on log files created
         by the syslogger process.
        </para>
       </listitem>

       <listitem>
        <para>
         Add <literal>restart_after_crash</> parameter
        </para>
        <para>
         Normally, we automatically restart after a backend crash, but in
         some cases when PostgreSQL is invoked by clusterware it may be
         desirable to suppress this behavior, so we now provide an option which
         does that.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Teach replication connections to respect the value of
         log_connections</emphasis>
        </para>
        <para>
         Previously, they were always logged.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Log restartpoints in the same fashion as
         checkpoints</emphasis>
        </para>
        <para>
         Previously, less information was logged for restartpoints.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>By default, set wal_buffers to a reasonable value, based
         on the setting for shared_buffers</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Administration and Monitoring</title>
      <itemizedlist>

       <listitem>
        <para>
         Instrument checkpoint sync calls
        </para>
       </listitem>

       <listitem>
        <para>
         Use the same lexer for recovery.conf that has been used for
         <filename>postgresql.conf</> (Dimitri Fontaine)
        </para>

        <para>
         Among other things, this allows values in recovery.conf to be unquoted.
        </para>
       </listitem>

       <listitem>
        <para>
         Add column buffers_backend_fsync to pg_stat_bgwriter
        </para>
       </listitem>

       <listitem>
        <para>
         Add monitoring function pg_last_xact_replay_timestamp()
        </para>
       </listitem>

       <listitem>
        <para>
         Allow pg_ctl to register the service in either AUTO or DEMAND start
         type
        </para>
       </listitem>

       <listitem>
        <para>
         Support host names and host key word <literal>all</literal>
         in <filename>pg_hba.conf</filename>
        </para>
       </listitem>

       <listitem>
        <para>
         Make EXPLAIN show the function call expression of a
         FunctionScan plan node, but only in VERBOSE mode
        </para>
       </listitem>

       <listitem>
        <para>
         Make EXPLAIN print PARAM_EXEC Params as
         the referenced expressions, rather than just $N
        </para>
       </listitem>

       <listitem>
        <para>
         Add vacuum and analyze counters to pg_stat_*_tables
         views
        </para>
       </listitem>

       <listitem>
        <para>
         Add stats functions and views to provide access to a
         transaction's own statistics counts
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Implement remaining fields of
         information_schema.sequences view</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add a "conflicts" column to pg_stat_database</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>New system view pg_stat_database_conflicts</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>New system view pg_stat_replication</emphasis>
        </para>
        <para>
         This view shows which replication slaves are connected to the master,
         and reports their status and replication progress.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>When an autovacuum worker (other than one performing an
         anti-wraparound vacuum) is unable to obtain a lock on the target
         relation without blocking, skip the relation</emphasis>
        </para>
        <para>
         This avoids pinning down an autovacuum worker.  The next autovacuum
         cycle will try again. 
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Track time of last statistics reset on databases and
         bgwriter</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Security</title>
      <itemizedlist>

       <listitem>
        <para>
         Add SECURITY LABEL command
        </para>
        <para>
         This is intended as infrastructure to support integration
         with label-based mandatory access control systems such as
         SE-Linux.
        </para>
       </listitem>

       <listitem>
        <para>
         Add server authentication over Unix-domain
         sockets
        </para>
        <para>
         This adds a libpq connection parameter <literal>requirepeer</> that
         specifies the user name that the server process is expected to run
         under.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add REPLICATION privilege for ROLEs</emphasis>
        </para>
        <para>
         This makes it possible for replication to be performed by a
         non-superuser account.
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Built-in Functions</title>
      <itemizedlist>

       <listitem>
        <para>
         Add pg_read_binary_file() and whole-file-at-once
         versions of pg_read_file()
        </para>
       </listitem>

       <listitem>
        <para>
         Add new function format(), for sprintf-like string formatting
        </para>
       </listitem>

       <listitem>
        <para>
         Add pg_describe_object() function to obtain textual
         descriptions of objects as stored in pg_depend
        </para>
       </listitem>

       <listitem>
        <para>
         Accept <literal>public</literal> as a pseudo-role
         name in <literal>has_table_privilege()</literal> and friends
         to see if a particular privilege has been granted to
         <literal>PUBLIC</literal>
        </para>
       </listitem>

       <listitem>
        <para>
         Add string functions: concat(), concat_ws(), left(),
         right(), and reverse()
        </para>
       </listitem>

       <listitem>
        <para>
         Add three-parameter forms of array_to_string and
         string_to_array
        </para>
       </listitem>

       <listitem>
        <para>
         Add XMLEXISTS function
        </para>
       </listitem>

       <listitem>
        <para>
         Add xpath_exists() function
        </para>
        <para>
         This is equivalent to XMLEXISTS except that it offers support for
         namespace mapping.
        </para>
       </listitem>

       <listitem>
        <para>
         Add xml_is_well_formed, xml_is_well_formed_document,
         xml_is_well_formed_content functions to the core XML
         code
        </para>
        <para>
         These supersede a version previously offered by contrib/xml2.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Change pg_last_xlog_receive_location not to move
         backwards</emphasis>
        </para>
       </listitem>

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

       <listitem>
        <para>
         Allow numeric to use a more compact, 2-byte header in
         many cases
        </para>
       </listitem>

       <listitem>
        <para>
         Add support for dividing money by money (yielding a
         float8 result) and for casting between money and numeric
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Server Tools</title>
      <itemizedlist>

       <listitem>
        <para>
         Add options to force quoting of all
         identifiers
        </para>
        <para>
         This includes a quote_all_identifiers parameter which affects the
         behavior of the backend, and a --quote-all-identifiers argument to
         pg_dump and pg_dumpall which sets the parameter and also affects the
         quoting done internally by those applications.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add a directory output format to pg_dump</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title><application>psql</></title>
      <itemizedlist>

       <listitem>
        <para>
         Add <quote>S</quote> option to \dn command in <application>psql</>
        </para>
        <para>
         System schemas are now hidden by default by \dn.
        </para>
       </listitem>

       <listitem>
        <para>
         Add \conninfo command to <application>psql</>, to show current connection
         info
        </para>
       </listitem>

       <listitem>
        <para>
         Extend <application>psql</>'s \e and \ef commands so that a line number
         can be specified, and the editor's cursor will be initially placed
         on that line
        </para>
        <para>
         To avoid assumptions about what switch the user's editor takes for
         this purpose, there is a new <application>psql</> variable EDITOR_LINENUMBER_SWITCH
         with (at present) no default value.
        </para>
       </listitem>
       <listitem>
        <para>
         Add a \sf (show function) command to <application>psql</>, for those
         times when you need to look at a function but don't wish to fire up
         an editor
        </para>
       </listitem>

       <listitem>
        <para>
         Make <application>psql</> distinguish between unique indices and unique
         constraints in \d printout
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add a \dL command to <application>psql</>, to list procedural
         languages</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow <application>psql</> to automatically deduce the client encoding from
         the locale</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>libpq</title>
      <itemizedlist>

       <listitem>
        <para>
         Add PQlibVersion() function
        </para>
       </listitem>

       <listitem>
        <para>
         When reporting the server as not responding, if the
         hostname was supplied, also print the IP address
        </para>
        <para>
         This allows IPv4 and IPv6 failures to be distinguished.  Also
         useful when a hostname resolves to multiple IP addresses.
        </para>
       </listitem>

       <listitem>
        <para>
         Add functions PQping and PQpingParams to allow
         detection of the server's status, including a status where
         the server is running but refuses ordinary connections
        </para>
        <para>
         pg_ctl uses the new function.  This fixes the case where
         pg_ctl reports that the server is not running (cannot
         connect) but in fact it is running.
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>ecpg</title>
      <itemizedlist>
       <listitem>
        <para>
         <emphasis>Allow ecpg to accept dynamic cursor names even in WHERE
         CURRENT OF clauses</emphasis>
        </para>
       </listitem>
      </itemizedlist>
    </sect3>
    <sect3>
      <title>Procedural Languages</title>
      <sect4>
       <title>PL/pgSQL</title>
      <itemizedlist>

       <listitem>
        <para>
         Modify the handling of RAISE without parameters so that
         the error it throws can be caught in the same places that could
         catch an ordinary RAISE ERROR in the same location
        </para>
        <para>
         The previous coding insisted on throwing the error from the block
         containing the active exception handler; which is arguably more
         surprising, and definitely unlike Oracle's behavior.
        </para>
       </listitem>

       <listitem>
        <para>
         Remove ancient PL/pgSQL line numbering hack
        </para>
        <para>
         PL/pgSQL used to count the second line of the function body as
         <quote>line 1</>, if the first line was zero-length.
         While this hack arguably has some benefit in terms of making
         PL/pgsql's line numbering match the programmer's expectations, it
         also makes PL/pgsql inconsistent with the remaining PLs, making it
         difficult for clients to reliably determine where the error
         actually is.  On balance, it seems better to be consistent.
        </para>
       </listitem>

      </itemizedlist>
      </sect4>

      <sect4>
       <title>PL/Perl</title>

       <itemizedlist>
        <listitem>
         <para>
          Allow generic record arguments to PL/Perl functions
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Convert PostgreSQL arrays passed to PL/perl functions to
          Perl arrays</emphasis>
         </para>
        </listitem>
       </itemizedlist>
      </sect4>

      <sect4>
       <title>PL/Python</title>
       <itemizedlist>

        <listitem>
         <para>
          <emphasis>Fix an error when a set-returning function fails halfway
          through</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Make plpy.Fatal() raise FATAL, rather than ERROR</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Skip dropped attributes when converting Python objects to
          tuples</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Improve the handling of exceptions</emphasis>
         </para>
         <para>
          Fix the way that exceptions are handled by the plpy module for Python
          3.  Get rid of the global variable holding the error state, and
          instead arrange to report PostgreSQL errors to Python immediately.
          Call PLy_spi_execute_fetch_result inside the try/catch block, so that
          errors from fetching tuples are correct reported as errors in the
          SPI call.  Use the built-in TypeError, not SPIError, for errors
          having to do with argument counts or types.  Use SPIError, not simply
          plpy.Error, for errors in PLy_spi_execute_plan.  Do not set
          a Python exception if PyArg_ParseTuple failed, as it already sets
          the correct exception.
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Improve error reporting</emphasis>
         </para>
         <para>Better error messages for errors in compiling anonymous
          PL/Python blocks.  Avoid prefixing error messages with the string
          "PL/Python: ", which is redundant, given the error
          context.  Provide a separate exception class for each error code
          the backend defines, and make it possible to get the SQLSTATE from
          the exception object.  Report Python errors from iterators
          using PLy_elog, so that the Python exception is included in the
          exception, and to avoid setting the errcode to
          ERRCODE_DATA_EXCEPTION.
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Check PL/Python functions for syntax errors at creation
          time</emphasis>
         </para>
         <para>
          Previously, even gross syntax errors would not be detected until
          the function was executed.
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Allow Python try/catch blocks to catch exceptions arising
          from SPI calls</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Invalidate PL/python functions with composite type
          arguments when the type changes</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Add quoting functions plpy.quote_ident, plpy.quote_literal,
          and plpy.quote_nullable</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Support table functions</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Add a plpy.subtransaction() context manager</emphasis>
         </para>
        </listitem>

        <listitem>
         <para>
          <emphasis>Assorted code cleanup</emphasis>
         </para>
         <para>
          We now use HTABs instead of Python dictionary objects to cache
          procedures.  palloc is used in TopMemoryContext instead of malloc.
          Avoid use of undocumented API PyObject_NEW.  Free plan values in
          the PlyPlanObject dealloc function.  Add braces around an if block,
          for readability.  Refactor PLy_spi_prepare to save two levels of
          indentation.  Avoid palloc(0).
         </para>
        </listitem>
       </itemizedlist>
      </sect4>
    </sect3>

    <sect3>
      <title>Additional Supplied Modules</title>
      <itemizedlist>

       <listitem>
        <para>
         New module contrib/auth_delay
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>New module contrib/sepgsql, an SE-Linux integration for
         PostgreSQL</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         Updates to contrib/isn ISBN tables
        </para>
       </listitem>

       <listitem>
        <para>
         Add the ability to compute per-statement latencies (ie,
         average execution times) to pgbench
        </para>
       </listitem>

       <listitem>
        <para>
         Teach levenshtein() about multi-byte
         characters
        </para>
       </listitem>

       <listitem>
        <para>
         Add btree_gist support for searching on <quote>not
         equals</quote>
        </para>
       </listitem>

       <listitem>
        <para>
         Add ssl_cipher() and ssl_version() functions to
         contrib/sslinfo
        </para>
       </listitem>

       <listitem>
        <para>
         Remove the arbitrary (and undocumented) limit on the
         number of parameter=value pairs that can be handled by
         xslt_process()
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>New module contrib/pg_test_fsync, replacing
         src/tools/test_fsync</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>In contrib/pageinspect, fix the heap_page_item to return
         infomasks as 32 bit values</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>In contrib/btree_gist, support KNN GiST searches</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>In contrib/pg_trgm, support LIKE, ILIKE, and KNN GiST
         searches</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Several improvements to contrib/intarray</emphasis>
        </para>
        <para>
         Correct the behavior of array containment operators, so that an empty
         array is contained in any other array.  Fix bogus failures where
         operators would claim that nulls were present when they really
         weren't.  Remove arbitrary restriction to 1-D arrays.
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Fix pg_upgrade not to insist on pg_dumpall and psql in the
         old cluster, since we don't need them, but do check for pg_resetxlog
         in the old and new clusters, since we do.  Avoid a useless attempt
         to call pg_config in the old cluster.</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
    <sect3>
      <title>Source Code, Build Options</title>
      <itemizedlist>

       <listitem>
        <para>
         Rewrite the GiST insertion logic so that the
         post-recovery cleanup stage to finish incomplete inserts or
         splits is not needed anymore
        </para>
       </listitem>

       <listitem>
        <para>
         Add support for collecting <quote>minidump</quote>-style crash dumps
         on Windows
        </para>
       </listitem>

       <listitem>
        <para>
         Replace pg_class.relistemp column with relpersistence
        </para>

        <para>
         This is for upcoming work on unlogged and global temporary tables.
        </para>
       </listitem>

       <listitem>
        <para>
         GNU make 3.80 or newer is now required
        </para>
       </listitem>

       <listitem>
        <para>
         Improved support for parallel make, make -k, and make -q
        </para>
       </listitem>

       <listitem>
        <para>
         Include the backend ID in the relpath of temporary
         relations
        </para>
        <para>
         This allows us to reliably remove all leftover temporary relation
         files on cluster startup without reference to system catalogs or
         WAL; therefore, we no longer include temporary relations in
         XLOG_XACT_COMMIT and XLOG_XACT_ABORT WAL records.
        </para>
       </listitem>

       <listitem>
        <para>
         Rewrite COMMENT ON <replaceable>object</> code for better
         modularity, and add necessary locking
        </para>
       </listitem>

       <listitem>
        <para>
         Add a hook in ExecCheckRTPerms() for eventual use by
         external security-checking modules
        </para>
       </listitem>

       <listitem>
        <para>
         Standardize names and calling conventions of
         get_whatever_oid functions
        </para>
       </listitem>

       <listitem>
        <para>
         Make NestLoop plan nodes pass outer-relation variables
         into their inner relation using the general PARAM_EXEC executor
         parameter mechanism, rather than the ad-hoc kluge of passing the
         outer tuple down through ExecReScan
        </para>
       </listitem>

       <listitem>
        <para>
         Make details of the Numeric representation private to
         numeric.c
        </para>
       </listitem>

       <listitem>
        <para>
         Suppress some compiler warnings from
         <literal>clang</>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Allow make check in PL directories</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>Add a make check-world target</emphasis>
        </para>
       </listitem>

       <listitem>
        <para>
         <emphasis>PGXS support for contrib/hstore</emphasis>
        </para>
       </listitem>

      </itemizedlist>
    </sect3>
  </sect2>
 </sect1>

