<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.49 2010/08/17 04:37:21 petere Exp $ -->

 <sect1 id="release-9-0">
  <title>Release 9.0</title>

  <note>
   <title>Release date</title>
   <simpara>2010-??-??</simpara>
  </note>

  <para>CURRENT AS OF 2010-07-29</para>

  <sect2>
   <title>Overview</title>

   <para>
    Based on overwhelming user demand, this release of
    <productname>PostgreSQL</> adds features that have been requested
    for years, like easy-to-use replication, a mass permission
    facility, and anonymous blocks. While past major releases have
    been conservative in their scope, this release shows a
    bold new desire to provide facilities that new and existing
    users of <productname>PostgreSQL</> will embrace. This has all
    been done with few incompatibilities. Major enhancements are:
   </para>

   <itemizedlist>

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

    <listitem>

     <para>
      Built-in, binary, log-based replication.  This advance consists of two
      features: Hot Standby allows continuous archive standby database servers
      to accept read-only queries, and Streaming Replication allows continuous
      archive (<acronym>WAL</>) files to be streamed over a network port to a
      standby database server.
     </para>
    </listitem>

    <listitem>
     <para>
      Easier database object permissions management. <link
      linkend="SQL-GRANT"><command>GRANT</>/<command>REVOKE
      IN SCHEMA</></link> supports mass permissions changes, and
      the <link linkend="SQL-ALTERDEFAULTPRIVILEGES"><command>ALTER
      DEFAULT PRIVILEGES</></link> command controls privileges
      of all newly-created objects.  Large object permissions now
      support <command>GRANT</>/<command>REVOKE</> as well.
     </para>
    </listitem>

    <listitem>
     <para>
      Add support for compiling on <link
      linkend="install-win32-full">64-bit
      <productname>Windows</></link> and running in 64-bit
      mode.
     </para>
    </listitem>

    <listitem>
     <para>
      Broadly enhanced stored procedure support.
      The <link linkend="SQL-DO"><command>DO</></link> statement permits
      anonymous code blocks.  Functions can now be called using named
      parameters.  PL/pgSQL is now installed by default, and PL/Perl and
      PL/Python have been enhanced in several ways, including support for
      Python3.
     </para>
    </listitem>

    <listitem>
     <para>
      More advanced reporting queries with additional windowing functions
      (PRECEDING and FOLLOWING) and the ability to ORDER BY inside aggregate
      functions.
     </para>
    </listitem>

    <listitem>
     <para>
      Triggers now support two new features,
      SQL-compliant <link
      linkend="SQL-CREATETRIGGER">per-column triggers</link>, and
      conditional trigger execution.
     </para>
    </listitem>

    <listitem>
     <para>
      <link linkend="SQL-CREATETABLE-compatibility">Deferrable
      unique constraints</link>. Mass updates to unique keys are now possible
      without trickery.
     </para>
    </listitem>

    <listitem>
     <para>
      New and enhanced security features, including RADIUS authentication,
      LDAP authentication improvements, and the new <filename>checkpassword</> optional module
      for testing password strength.
     </para>
    </listitem>

    <listitem>
     <para>
      The <link linkend="SQL-LISTEN"><command>LISTEN</></link>/<link
      linkend="SQL-NOTIFY"><command>NOTIFY</></link>
      feature has been overhauled to make it into
      a high-performance event queuing system.  It now stores
      events in a memory-based queue, and it now allows delivery
      of a string payload to listeners with each event.
     </para>
    </listitem>

    <listitem>
     <para>
      Add <link linkend="pgupgrade"><filename>contrib/pg_upgrade</></link>
      to support in-place upgrades from 8.3 or 8.4 to 9.0.
     </para>
    </listitem>

    <listitem>
     <para>
      Multiple performance enhancements for specific types of queries,
      including join elimination, which optimizes automatically generated
      queries, such as those produced by object-relational mappers (ORMs).
     </para>
    </listitem>

    <listitem>
     <para>
      Exclusion constraints let database designers define uniqueness
      based on complex criteria, including for non-scalar data such
      as time periods, ranges and arrays.
     </para>
    </listitem>

    <listitem>
     <para>
      As part of our decade-long effort to eliminate the pain of VACUUM,
      <command>VACUUM FULL</> is now substantially faster by
      rewriting the entire table and
      indexes, rather than moving around single rows to compact space.
     </para>
    </listitem>

    <listitem>
     <para>
      <command>EXPLAIN</> plans are now available in JSON, XML, and YAML format, and include
      buffer utilization and other data not previously available.
     </para>
    </listitem>

    <listitem>
     <para>
      The <filename>hstore</> optional module has been improved with new functions and greater
      data capacity to make it a high-performance key-value store.
     </para>
    </listitem>

   </itemizedlist>

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

  </sect2>

  <sect2>

  <title>Migration to Version 9.0</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 9.0 contains a number of changes which selectively break backwards
   compatibility in order to support new features and code quality
   improvements.  Particularly, users who make extensive use of PL/pgSQL
   and/or PITR and Warm Standby should test their solutions for breakage.
   Observe the following incompatibilities:
  </para>

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

   <itemizedlist>

    <listitem>
     <para>
      Remove server variable <varname>add_missing_from</>, which was
      defaulted to off for many years (Tom Lane)
     </para>
    </listitem>

    <listitem>
     <para>
      Remove server variable <varname>regex_flavor</>, which
      was defaulted to <link
      linkend="posix-syntax-details"><literal>advanced</></link>
      (i.e., Perl compatible) for many years. (Tom Lane)
     </para>
    </listitem>

    <listitem>
     <para>
      It is now necessary to set <link
      linkend="guc-wal-level"><varname>wal_level</></link> to
      <literal>archive</> to do continuous archiving.
      (Heikki Linnakangas)
     </para>
    </listitem>

    <listitem>
     <para>
      Adjust <link
      linkend="guc-log-temp-files"><varname>log_temp_files</></link> to
      use default file size units of kilobytes (Robert Haas)
     </para>
    </listitem>

   </itemizedlist>

  </sect3>

  <sect3>
   <title>Queries</title>
   <itemizedlist>

   <listitem>
    <para>
     When querying a <link linkend="ddl-inherit">parent table</link>,
     do not do additional permission checks on child tables
     returned as part of the query (Peter Eisentraut)
    </para>

    <para>
     The SQL standard specifies this behavior.
    </para>
   </listitem>

   <listitem>
    <para>
     Have fractional seconds conversion truncate rather than
     round when using float-based dates/times (Tom Lane)
    </para>
   </listitem>

   </itemizedlist>

  </sect3>

  <sect3>
   <title>String Handling</title>
   <itemizedlist>

   <listitem>
    <para>
     Improve standards compliance of <link
     linkend="functions-similarto-regexp"><literal>SIMILAR TO</></link>
     patterns and SQL-style <function>substring()</> patterns (Tom Lane)
    </para>

    <para>
     This includes treating <literal>?</> and <literal>{...}</> as
     pattern metacharacters, while they were simple literal characters
     before; that corresponds to new features added in SQL:2008.
     Also, <literal>^</> and <literal>$</> are now treated as simple
     literal characters; formerly they were treated as metacharacters,
     as if the pattern were following POSIX rather than SQL rules.
     Also, in SQL-standard <function>substring()</>, use of parentheses
     for nesting no longer interferes with capturing of a substring.
     Also, processing of bracket expressions (character classes) is
     now more standards-compliant.
    </para>
   </listitem>

   <listitem>
    <para>
     Reject negative length values in 3-parameter <link
     linkend="functions-string-sql"><function>substring()</></link>
     for bit strings, per the SQL standard (Tom Lane)
    </para>
   </listitem>

  </itemizedlist>

  </sect3>

  <sect3>
   <title>Object Renaming</title>
   <itemizedlist>

    <listitem>
     <para>
      Tighten enforcement of column renaming when a child table inherits
      the renamed column from an unrelated parent (KaiGai Kohei)
     </para>
    </listitem>

    <listitem>
     <para>
      No longer rename index names and index column names when table
      columns are renamed (Tom Lane)
     </para>

     <para>
      Administrators still can rename such columns manually.  This change
      will require an update of the JDBC driver and possibly other drivers
      so that unique indexes are correctly recognized.
     </para>
    </listitem>

    <listitem>
     <para>
      <command>CREATE OR REPLACE FUNCTION</command> can no longer change
      the declared names of function parameters (Pavel Stehule)
     </para>

     <para>
      In order to support named-parameter calls, it is
      no longer allowed to change the aliases for input variables
      in the declaration of an existing function.  You now have to
      <command>DROP</command> and recreate the function.
     </para>
    </listitem>

   </itemizedlist>

  </sect3>

  <sect3>
   <title>PL/pgSQL</title>
   <itemizedlist>

    <listitem>
     <para>
      PL/pgSQL now throws an error if a variable name conflicts with a
      column name used in a query (Tom Lane)
     </para>

     <para>
      The former behavior was to bind to variable names in preference to
      query column names, which often resulted in surprising misbehavior.
      Throwing an error allows easy detection of ambiguous situations.
      Although it's recommended that functions encountering this type of
      error be modified to remove the conflict, the old behavior can be
      restored if necessary via the configuration parameter <link
      linkend="plpgsql-var-subst"><varname>plpgsql.variable_conflict</></link>,
      or via the per-function option <literal>#variable_conflict</>.
     </para>
    </listitem>

    <listitem>
     <para>
      PL/pgSQL no longer allows variable names that match SQL
      reserved words (Tom Lane)
     </para>

     <para>
      This is a consequence of aligning the PL/pgSQL parser to match the
      core SQL parser more closely.  If necessary,
      variable names can be double-quoted to avoid this restriction.
     </para>
    </listitem>

    <listitem>
     <para>
      PL/pgSQL now requires columns of composite results to match the
      expected type modifier as well as base type (Pavel Stehule, Tom Lane)
     </para>

     <para>
      For example, if a column of the result type is declared as
      <literal>NUMERIC(30,2)</>, it is no longer acceptable to return a
      <literal>NUMERIC</> of some other precision in that column.  Previous
      versions neglected to check the type modifier and would thus allow
      result rows that didn't actually conform to the declared restrictions.
     </para>
    </listitem>

    <listitem>
     <para>
      Remove PL/pgSQL's <literal>RENAME</> declaration option (Tom Lane)
     </para>

     <para>
      Instead of <literal>RENAME</>, use <link
      linkend="plpgsql-declaration-alias"><literal>ALIAS</></link>,
      which can now alias any variable, not just dollar sign
      parameter names (such as <literal>$1</>).
     </para>
    </listitem>
   </itemizedlist>

  </sect3>

  <sect3>
   <title>Other Incompatibilities</title>
   <itemizedlist>
    <listitem>
     <para>
      Remove support for platforms that don't have a working 64-bit
      integer data type (Tom Lane)
     </para>

     <para>
      It is believed all still-supported platforms have working 64-bit
      integer data types.
     </para>
    </listitem>

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

 <sect2>
  <title>Changes</title>
   <para>
    Version 9.0 has an unprecedented number of new major features,
    and over 200 enhancements, improvements, new commands,
    new functions, and other changes.
   </para>

  <sect3>
   <title>Server</title>

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

    <para>
     PostgreSQL's native standby capability has been expanded both to
     support read-only queries on standby slaves and to greatly reduce
     the lag between master and standby servers.  For many users, this
     will be a useful and low-administration form of replication, either
     for high availability or for horizontal scalability.
    </para>

    <itemizedlist>
     <listitem>
      <para>
       Allow a standby system to accept read-only queries
       (Simon Riggs, Heikki Linnakangas)
      </para>

      <para>
       This feature is called Hot Standby. There are new
       <filename>postgresql.conf</> and <filename>recovery.conf</>
       settings to enable this feature, as well as extensive
       <link linkend="hot-standby">documentation</link>.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow write-ahead log (<acronym>WAL</>) files to be streamed to a
       standby system (Fujii Masao, Heikki Linnakangas)
      </para>

      <para>
       This feature is called Streaming Replication.
       Previously <acronym>WAL</> files could be sent to standby systems only
       as 16 megabytes files; Streaming Replication allows master changes to be sent to the
       standby with very little delay. There are new <filename>postgresql.conf</>
       and <filename>recovery.conf</> settings to enable this
       feature, as well as extensive <link
       linkend="streaming-replication">documentation</link>.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link
       linkend="functions-recovery-info-table"><function>pg_last_xlog_receive_location()</></link>
       and <function>pg_last_xlog_replay_location()</>, which
       can be used to monitor standby server <acronym>WAL</>
       activity (Simon Riggs, Fujii Masao, Heikki Linnakangas)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Performance</title>

    <para>
     Version 9.0 also contains several performance and optimizer enhancements
     to improve specific uses of PostgreSQL and remedy certain poor-performing
     cases.
    </para>

    <itemizedlist>

     <listitem>
      <para>
       Improve performance of finding inherited child tables (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow per-tablespace sequential and random page cost variables
       (<varname>seq_page_cost</>/<varname>random_page_cost</>) via
       <link linkend="SQL-ALTERTABLESPACE"><command>ALTER TABLESPACE
       ... SET/RESET</></link> (Robert Haas)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve performance of <link
       linkend="SQL-TRUNCATE"><command>TRUNCATE</></link> when
       used in the same transaction as table creation (Tom Lane)
      </para>
     </listitem>

     </itemizedlist>

   </sect4>

   <sect4>
    <title>Optimizer</title>

    <itemizedlist>

     <listitem>
      <para>
       Remove unnecessary <link linkend="queries-join">outer
       joins</link> (Robert Haas)
      </para>

      <para>
       Outer joins where the inner side is unique and not referenced in
       the query are unnecessary and are therefore now removed.  This will
       accelerate many automatically generated queries, such as those created
       by object-relational mappers (ORM).
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <literal>IS NOT NULL</> restrictions to use indexes (Tom Lane)
      </para>

      <para>
       This is particularly useful for finding
       <function>MAX()</>/<function>MIN()</> values in indexes that also
       contain null values.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve optimizer equivalence detection of &lt;&gt; <type>boolean</>
       tests (Tom Lane)
      </para>
     </listitem>
    </itemizedlist>
   </sect4>

   <sect4>
    <title><link linkend="geqo">GEQO</link></title>
    <itemizedlist>

     <listitem>
      <para>
       Use the same random seed every time GEQO plans a query (Andres
       Freund)
      </para>

      <para>
       While the Genetic Query Optimizer (GEQO) still selects
       random plans, it now selects the same random plans for
       identical queries. You can modify <link
       linkend="guc-geqo-seed"><varname>geqo_seed</></link> to randomize
       the starting value of the random plan generator.
      </para>

      <para>
       This gives GEQO query response times and resource usage
       repeatability and predictability.
      </para>

     </listitem>

     <listitem>
      <para>
       Improve GEQO plan selection (Tom Lane).
      </para>

      <para>
       This avoids the rare error, "failed to make a valid plan".
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Optimizer Statistics</title>
    <itemizedlist>

     <listitem>
      <para>
       Improve <link linkend="SQL-ANALYZE"><command>ANALYZE</></link>
       to support inheritance-tree statistics (Tom Lane)
      </para>

      <para>
       This is particularly useful for partitioned tables.  However,
       autovacuum does not yet properly analyze parent tables based on
       child table changes.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve <link linkend="routine-vacuuming">autovacuum</link>
       detection of when re-analyze is necessary (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve optimizer statistics for greater/less-than comparisons
       (Tom Lane)
      </para>

      <para>
       When looking up optimizer statistics for greater/less-than comparisons,
       if the comparison value is in the first or last histogram bucket,
       use an index to generate the actual statistics. This is particularly
       useful for columns that are always increasing, and hence often have
       inaccurate statistics.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow setting of distinct statistics using <link
       linkend="SQL-ALTERTABLE"><command>ALTER TABLE</></link>
       (Robert Haas)
      </para>

      <para>
       This allows user-override of the number or percentage of distinct
       values for a column and optionally its child tables. This value
       is normally computed by <command>ANALYZE</>.  Database administrators
       can use this feature to fix some poor statistics, especially on
       tables with millions or billions of rows.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Authentication</title>
    <para>
     Version 9.0 further extends PostgreSQL's support for multiple
     authentication methods, including RADIUS and improved LDAP support.
    </para>

    <itemizedlist>

     <listitem>
      <para>
       Add support for <link
       linkend="auth-radius"><acronym>RADIUS</></link> (Remote
       Authentication Dial In User Service) authentication
       (Magnus Hagander)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <link linkend="auth-ldap"><acronym>LDAP</></link>
       (Lightweight Directory Access Protocol) authentication
       to operate in "search/bind" mode (Robert Fleming, Magnus)
      </para>

      <para>
       This allows the user to be looked up first, then the system uses
       the <acronym>DN</> (Distinguished Name) returned for that user.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link
       linkend="auth-pg-hba-conf"><literal>samehost</></link>
       and <literal>samenet</> designations to
       <filename>pg_hba.conf</> (Stef Walter)
      </para>

      <para>
       These match the server's <acronym>IP</> address and network address
       respectively.
      </para>
     </listitem>

     <listitem>
      <para>
       Pass trusted SSL root certificate names to the client so the client
       can return an appropriate client certificate (Craig Ringer)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Monitoring</title>
    <para>
     With increased use of PostgreSQL in high-end production systems,
     users need increased monitoring.  PostgreSQL 9.0 continues to add
     more ways to monitor PostgreSQL applications.
    </para>

    <itemizedlist>

     <listitem>
      <para>
       Add the ability for clients to set an <link
       linkend="libpq-connect-application-name">application
       name</link>, which is displayed in
       <structname>pg_stat_activity</> (Dave Page)
      </para>

      <para>
       This allows DBAs to characterize database traffic
       and troubleshoot problems by source application.
      </para>
     </listitem>

     <listitem>
      <para>
       Add an SQL state option (<literal>%e</>) to <link
       linkend="guc-log-line-prefix"><varname>log_line_prefix</></link>
       (Guillaume Smet)
      </para>

      <para>
       This allows users to compile statistics on errors and messages
       by type.
      </para>

     </listitem>

     <listitem>
      <para>
       Write to the Windows event log in <acronym>UTF16</> encoding
       (Itagaki Takahiro)
      </para>

      <para>
       Now there is true multilingual support for PostgreSQL log messages
       on Windows.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Statistics Counters</title>
    <itemizedlist>

     <listitem>
      <para>
       Add <link
       linkend="monitoring-stats-funcs-table"><function>pg_stat_reset_shared('bgwriter')</></link>
       to reset the cluster-wide shared statistics of the
       background writer (Greg Smith)
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link
       linkend="monitoring-stats-funcs-table"><function>pg_stat_reset_single_table_counters()</></link>
       and <function>pg_stat_reset_single_function_counters()</>
       to allow the resetting of statistics counters for individual
       tables and indexes (Magnus Hagander)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Allow setting of configuration variables based on <link
       linkend="sql-alterrole">database/role</link>
       combinations (Alvaro Herrera)
      </para>

      <para>
       Previously only per-database and per-role setting were possible,
       not combinations. All role and database settings are now stored
       in the new <structname>pg_db_role_setting</> system table. A new
       <application>psql</> <literal>\drds</> command shows these settings.
       Backwards-compatible system views do not show this information.
       The primary use of this feature is setting schema
       <link linkend="guc-search-path"><varname>search_path</varname></link>.
      </para>

     </listitem>

     <listitem>
      <para>
       Add Boolean variable <link
       linkend="guc-bonjour"><varname>bonjour</></link>, which
       controls whether a Bonjour-enabled binary advertises
       itself via <productname>Bonjour</> (Tom Lane)
      </para>

      <para>
       The default is off, meaning it does not advertise.
      </para>
     </listitem>

     <listitem>
      <para>
       Add Boolean variable <link
       linkend="guc-enable-material"><varname>enable_material</></link>, which
       controls the use of materialize nodes in the optimizer
       (Robert Haas)
      </para>

      <para>
       The default is on.
      </para>
     </listitem>

     <listitem>
      <para>
       Log changed parameter values when <filename>postgresql.conf</> is
       reloaded (Peter Eisentraut)
      </para>

      <para>
       This lets DBAs and security staff audit when database settings
       were changed.
      </para>

     </listitem>

     <listitem>
      <para>
       Add proper permissions for custom variables (Tom Lane)
      </para>

      <para>
       Custom variables can now only be created by super-users,
       but can be modified by ordinary users if variable
       permissions allow it. This makes custom variables
       appropriate for security settings. Previously, any user
       could create or modify custom variables.
      </para>
     </listitem>

    <listitem>
     <para>
      Adjust <link
      linkend="guc-log-temp-files"><varname>log_temp_files</></link> to
      use default file sizes units of kilobytes (Robert Haas)
     </para>

     <para>
      Previously this setting defaulted to bytes if no units were
      specified.
     </para>
    </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

  <sect3>
   <title>Queries</title>
   <itemizedlist>

    <listitem>
     <para>
      Do <link linkend="SQL-FOR-UPDATE-SHARE"><command>SELECT
      FOR UPDATE</>/<literal>SHARE</></link> processing after
      applying <literal>LIMIT</>, so the number of rows returned
      is always predictable (Tom Lane)
     </para>

     <para>
      Previously, concurrent transactions could potentially cause
      <command>SELECT</> to return fewer rows than specified by
      <literal>LIMIT</>. <literal>FOR UPDATE</> can still affect
      <literal>ORDER BY</> ordering, but this can be corrected by using
      <literal>FOR UPDATE</> in a subquery.
     </para>
    </listitem>

    <listitem>
     <para>
      Allow mixing of traditional and SQL-standard <link
      linkend="SQL-LIMIT"><literal>LIMIT</>/<literal>OFFSET</></link>
      syntax in the same query (Tom Lane)
     </para>
    </listitem>

    <listitem>
     <para>
      Increase the supported frame options in <link
      linkend="SQL-WINDOW">window functions</link> (Hitoshi
      Harada)
     </para>

     <para>
      This allows frames (<literal>RANGE</> or <literal>ROWS</>) to start
      with <literal>CURRENT ROW</>, and to use the <literal>ROWS n
      PRECEDING</>/<literal>FOLLOWING</> clause.
     </para>
    </listitem>

    <listitem>
     <para>
      Have <command>SELECT</> and <command>CREATE TABLE AS</> return
      row counts to the client
      (Boszormenyi Zoltan)
     </para>

     <para>
      For drivers that support this feature, this saves an entire
      round-trip to the client, allowing result counts and pagination
      to be calculated without a second <command>COUNT</command> query.
     </para>

     <para>
      <application>psql</> does not display these counts.
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title>Unicode Strings</title>
    <itemizedlist>

     <listitem>
      <para>
       Add Unicode surrogate pair (dual 16-bit) support to
       <link
       linkend="sql-syntax-strings-uescape"><literal>U&amp;</></link>
       strings and identifiers (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow Unicode escapes in <link
       linkend="sql-syntax-strings-escape"><literal>E'...'</></link>
       strings (Marko Kreen)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

    <listitem>
     <para>
      Speed up <link linkend="SQL-CREATEDATABASE"><command>CREATE
      DATABASE</></link> by deferring flushes to disk (Andres
      Freund, Greg Stark)
     </para>
    </listitem>

    <listitem>
     <para>
      Allow <link linkend="SQL-COMMENT">comments</link> on
      columns only of tables, views, and composite types, not other
      objects like indexes and <acronym>TOAST</> tables (Tom Lane)
     </para>
    </listitem>

    <listitem>
     <para>
      Allow the creation of <link
      linkend="SQL-CREATETYPE-enum">enumerate types</link> with
      no labels (Bruce Momjian)
     </para>

     <para>
      This is useful for supporting binary upgrades.
     </para>
    </listitem>

    <listitem>
     <para>
      Have columns defined with storage type <literal>MAIN</> remain on
      the main heap page unless it cannot fit (Kevin Grittner)
     </para>

     <para>
      Previously <literal>MAIN</> values were forced to <acronym>TOAST</>
      tables until the row size was one-quarter of the page size.
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title><command>ALTER</></title>
    <itemizedlist>

     <listitem>
      <para>
       Add <link linkend="SQL-ALTERDEFAULTPRIVILEGES"><command>ALTER
       DEFAULT PRIVILEGES</></link> command to control privileges
       of newly-created objects (Petr Jelinek)
      </para>

      <para>
       This greatly simplifies the assignment of object privileges in
       a complex database application.  Defaults currently support tables,
       views, sequences, and functions. Defaults may be assigned on a
       per-schema basis or database-wide.
      </para>
     </listitem>

     <listitem>
      <para>
       Implement <literal>IF EXISTS</> for <literal>DROP COLUMN</> and
       <literal>DROP CONSTRAINT </> (Andres Freund)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <command>ALTER TABLE</> commands which rewrite tables to skip
       <acronym>WAL</> logging (Itagaki Takahiro)
      </para>

      <para>
       Such operations either complete fully or are rolled back, so
       <acronym>WAL</> archiving can be skipped, unless running in continuous
       archiving mode.  This reduces I/O overhead and improves performance.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add support for copying <literal>COMMENTS</> and <literal>STORAGE</>
       to the <command>CREATE TABLE ... LIKE INCLUDING</> command (Itagaki
       Takahiro)
      </para>
     </listitem>

     <listitem>
      <para>
       Add support for copying all attributes to the <command>CREATE
       TABLE LIKE INCLUDING</> command (Itagaki Takahiro)
      </para>
     </listitem>

     <listitem>
      <para>
       Add the SQL-standard <command>CREATE TABLE ... OF type</> command
       (Peter Eisentraut)
      </para>

      <para>
       This allows the creation of a table to match an existing composite
       type. Additional constraints and defaults can be specified in the
       command.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Constraints</title>
    <itemizedlist>

     <listitem>
      <para>
       Add <link linkend="SQL-CREATETABLE-compatibility">deferrable
       unique constraints</link> (Dean Rasheed)
      </para>

      <para>
       This allows <command>UPDATE tab SET col = col + 1</> to work reliably
       on columns that have unique indexes or are marked as primary keys.
       If the constraint is specified as <literal>DEFERRABLE</> it will be
       checked at the end of the statement, rather than after each row is
       updated. The constraint check may also be deferred until the end of the
       current transaction, allowing updates to be spread over multiple SQL
       commands.
      </para>
     </listitem>

     <listitem>
      <para>
       Exclusion Constraints: generalize uniqueness constraints by allowing arbitrary operator
       comparisons, not just equality (Jeff Davis)
      </para>

      <para>
       This is enabled with the <link
       linkend="SQL-CREATETABLE-EXCLUDE"><command>CREATE
       TABLE CONSTRAINT ... EXCLUDE</></link> clause. While
       uniqueness checks could be specified using this syntax,
       the real value of this feature is in using complex
       operators that do not have built-in constraints.
      </para>

      <para>
       The primary use of exclusion constraints is to allow defining
       non-overlapping uniqueness, such as for time periods, arrays
       or ranges of values. This supports data integrity at the
       table level for calendaring, time-management, and scientific
       applications.
      </para>

     </listitem>

     <listitem>
      <para>
       Improve the constraint violation error message to report the values
       causing the failure (Itagaki Takahiro)
      </para>

      <para>
       For example, a uniqueness constraint violation now reports <literal>Key
       (x)=(2) already exists</>.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add the ability to make mass permission changes per
       schema using the new <link
       linkend="SQL-GRANT"><command>GRANT</>/<command>REVOKE
       IN SCHEMA</></link> clause (Petr Jelinek)
      </para>

      <para>
       This simplifies the assignment of object permissions
       and makes it easier to utilize database roles for application
       data security.
      </para>

     </listitem>

     <listitem>
      <para>
       Add the ability to control large object permissions with
       <command>GRANT</>/<command>REVOKE</> (KaiGai Kohei)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

   <itemizedlist>

    <listitem>
     <para>
      Have <link linkend="SQL-LISTEN"><command>LISTEN</></link>/<link
      linkend="SQL-NOTIFY"><command>NOTIFY</></link> store events
      in a memory queue, rather than a system table (Joachim
      Wieland)
     </para>

     <para>
      LISTEN/NOTIFY may now be used as a full-featured, high-performance
      event queue system for PostgreSQL, with transactional support
      and guaranteed delivery.
     </para>
    </listitem>

    <listitem>
     <para>
      Allow <link linkend="SQL-NOTIFY"><command>NOTIFY</></link>
      to pass an optional string to listeners (Joachim Wieland)
     </para>
    </listitem>

    <listitem>
     <para>
      Allow <link linkend="SQL-CLUSTER"><command>CLUSTER</></link>
      on all system tables (Tom Lane)
     </para>

     <para>
      Global system tables still cannot be clustered.
     </para>
    </listitem>

   </itemizedlist>

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

     <listitem>
      <para>
       Allow <literal>*</> as a parameter in <literal>FORCE QUOTE</> for
       <literal>COPY CSV</> (Itagaki Takahiro)
      </para>

      <para>
       This forces quotes for all <acronym>CSV</> output columns.
      </para>
     </listitem>

     <listitem>
      <para>
       Add new <command>COPY</> syntax that allows parameters to be
       specified in parentheses (Robert Haas, Emmanuel Cecchet)
      </para>

      <para>
       This allows greater flexibility for future <command>COPY</> options.
       The old syntax is still supported.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Allow <command>EXPLAIN</> output in <acronym>XML</>, <acronym>JSON</>,
       and <acronym>YAML</> formats (Robert Haas, Greg Sabino Mullane)
      </para>

      <para>
       The new output formats will support the development of new tools
       for analysis of EXPLAIN output.
      </para>
     </listitem>

     <listitem>
      <para>
       Add new <command>EXPLAIN (BUFFERS)</> to report query buffer
       activity (Itagaki Takahiro)
      </para>

      <para>
       This allows better query profiling for individual queries.
       log_*_stats log output, e.g. <link
       linkend="runtime-config-statistics-monitor">log_statement_stats</link>,
       no longer shows this information.
      </para>
     </listitem>

     <listitem>
      <para>
       Add hash usage information to <command>EXPLAIN</> output (Robert
       Haas)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <command>EXPLAIN</> options to be specified inside parentheses
       (Robert Haas)
      </para>

      <para>
       This allows for the expansion of <command>EXPLAIN</> options. The
       old syntax is still supported.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Change <command>VACUUM FULL</> to rewrite the entire table and
       indexes, rather than moving around single rows to compact space
       (Itagaki Takahiro, Tom Lane)
      </para>

      <para>
       The previous method was usually slower and caused index bloat.
       Note that the new method may use more disk space during VACUUM
       FULL.
      </para>

     </listitem>

     <listitem>
      <para>
       Add new <command>VACUUM</> syntax that allows parameters to be
       specified in parentheses (Itagaki Takahiro)
      </para>

      <para>
       This allows greater flexibility for future <command>VACUUM</>
       options. The old syntax is still supported.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Indexes</title>
    <itemizedlist>

     <listitem>
      <para>
       Allow an index to be auto-named by not supplying an index name to
       <link linkend="SQL-CREATEINDEX"><command>CREATE INDEX</></link> (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <link linkend="SQL-REINDEX"><command>REINDEX</></link>
       on system indexes (Tom Lane)
      </para>

      <para>
       WAS THIS POSSIBLE ON ANY SYSTEM TABLE BEFORE? NON-HARDWIRED ONES?
      </para>
     </listitem>

     <listitem>
      <para>
       Add <literal>point_ops</> operator class for GiST (Teodor Sigaev)
      </para>

      <para>
       This feature supports GiST indexing of point operations on polygons,
       circles, and other points, such as "point is in polygon".  Previously
       indexing only worked for bounding boxes.  This should make many
       PostGIS queries faster.
      </para>
     </listitem>

     <listitem>
      <para>
       Use red-black trees for <acronym>GIN</> index creation
       (Teodor Sigaev)
      </para>

      <para>
       Red-black trees are self-balanced.  This means much faster
       GIN index creation.
      </para>

     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

    <listitem>
     <para>
      Allow hex values to be specified in <link
      linkend="datatype-binary"><type>bytea</></link> strings
      (Peter Eisentraut)
     </para>

     <para>
      The variable <link
      linkend="guc-bytea-output"><varname>bytea_output</></link> controls
      if hex (default) or octal escapes are used for <type>bytea</>
      output. (SWITCH DEFAULT FOR BETA? PETER) Libpq's
      <function>PQescapeByteaConn()</> now uses the hex format
      for <productname>PostgreSQL</> 9.0 servers.
     </para>

     <para>
      The new hex format will be directly compatible with more applications
      which use binary data, allowing them to store and retrieve
      it without conversion.
     </para>

    </listitem>

    <listitem>
     <para>
      Allow <link
      linkend="guc-extra-float-digits">extra_float_digits</link>
      to be increased to <literal>3</> (Tom Lane)
     </para>

     <para>
      The previous maximum <varname>extra_float_digits</> was <literal>2</>.
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title><link linkend="textsearch">Full Text Search</link></title>
    <itemizedlist>

     <listitem>
      <para>
       Add prefix support for the full text search synonym dictionary
       (Teodor Sigaev)
      </para>
     </listitem>

     <listitem>
      <para>
       Add full text search filtering dictionaries (Teodor Sigaev)
      </para>

      <para>
       Filtering dictionaries allow tokens to be modified and passed to
       subsequent dictionaries.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow underscores in full text email addresses (Teodor Sigaev)
      </para>
     </listitem>

     <listitem>
      <para>
       Use more standards-compliant rules for <acronym>URL</>
       parsing (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

  <sect3>
   <title>Functions</title>
   <itemizedlist>

    <listitem>
     <para>
      Allow case-insensitive <link
      linkend="functions-posix-regexp">regular expression</link>
      matching with <acronym>UTF-8</> server encodings.
     </para>

     <para>
      Previously, only <acronym>ASCII</> characters and single-byte
      encodings worked properly. Multibyte encodings other than <acronym>UTF-8</>
      are still broken for case-insensitive regular expression
      matching.
     </para>
    </listitem>

    <listitem>
     <para>
      Allow function calls to supply parameter names and match them to named
      parameters in the function definition (Pavel Stehule)
     </para>

     <para>
      For example, if a function is defined to take parameters <literal>a</>
      and <literal>b</>, it can be called with <literal>func(a := 7, b
      := 12)</> or <literal>func(b := 12, a := 7)</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Add support for <link
      linkend="functions-formatting"><function>to_char()</></link>
      scientific notation output (<link
      linkend="functions-formatting-numeric-table"><literal>'EEEE'</></link>)
      (Pavel Stehule, Brendan Jurd)
     </para>
    </listitem>

    <listitem>
     <para>
      Have <function>to_char()</> honor <link
      linkend="functions-formatting-datetimemod-table"><literal>'FM'</></link>
      (fill mode) in <literal>'Y'</>, <literal>'YY'</>, and
      <literal>'YYY'</> specifications (Bruce Momjian, Tom Lane)
     </para>

     <para>
      It was already honored by <literal>'YYYY'</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Fix <function>to_char()</> to output the proper localized
      numeric and monetary characters on <productname>Windows</>
      (Hiroshi Inoue, Itagaki Takahir, Bruce Momjian)
     </para>
    </listitem>

    <listitem>
     <para>
      Correct calculations of <link
      linkend="functions-geometry-op-table">"overlap"</link>
      and "contains" operations over polygons (Teodor Sigaev)
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title>Aggregates</title>
    <itemizedlist>

     <listitem>
      <para>
       Allow aggregate functions to use <literal>ORDER BY</> (Andrew
       Gierth)
      </para>

      <para>
       For example, this is now supported, <literal>array_agg(a ORDER BY
       b)</>. This is useful for aggregates where the order of values is
       significant, and eliminates the need to have a subquery for
       the ordering.
      </para>
     </listitem>

     <listitem>
      <para>
       Add the <link
       linkend="functions-aggregate-table"><function>string_agg()</></link>
       aggregate function which aggregates values into a single
       string (Pavel Stehule)
      </para>

      <para>
       An optional second argument allows specification of a delimiter.
      </para>
     </listitem>

     <listitem>
      <para>
       Aggregate functions that are called with <literal>DISTINCT</> are
       now passed NULL values if the aggregate transition function is
       not marked as <literal>STRICT</> (Andrew Gierth)
      </para>

      <para>
       For example, <literal>agg(DISTINCT x)</> might pass NULL <literal>x</>
       values to <function>agg()</>.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Bit Strings</title>
    <itemizedlist>

     <listitem>
      <para>
       Add <link
       linkend="functions-binarystring-other"><function>get_bit()</></link>
       and <function>set_bit()</> functions for <type>bit</>
       strings, mirroring those for <type>bytea</> (Leonardo
       F)
      </para>
     </listitem>

     <listitem>
      <para>
       Implement <link
       linkend="functions-string-sql"><function>OVERLAY()</></link>
       (replace) for <type>bit</> strings and <type>bytea</>
       (Leonardo F)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add <link
       linkend="functions-admin-dbsize"><function>pg_table_size()</></link>
       and <function>pg_indexes_size()</> to provide a more
       user-friendly interface to the <function>pg_relation_size()</>
       function (Bernd Helmle)
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link
       linkend="functions-info-access-table"><function>has_sequence_privilege()</></link>
       for sequence permission checking (Abhijit Menon-Sen)
      </para>
     </listitem>

     <listitem>
      <para>
       Have <link linkend="information-schema">information
       schema</link> properly display date type octet lengths
       (Peter Eisentraut)
      </para>

      <para>
       The reported length is now the maximum octet length; previously,
       a huge value was reported.
      </para>
     </listitem>

     <listitem>
      <para>
       Speed up information schema privilege views (Joachim Wieland)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Implement anonymous functions using the <link
       linkend="SQL-DO"><command>DO</></link> statement, a.k.a anonymous
       blocks (Petr Jelinek, Joshua Tolley, Hannu Valtonen)
      </para>

      <para>
       This allows execution of server-side code without the need to create
       a new function and execute it.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow SQL-compliant <link
       linkend="SQL-CREATETRIGGER">per-column triggers</link>
       (Itagaki Takahiro)
      </para>

      <para>
       Such triggers are fired only if the specified columns are affected
       by the query, e.g. in <command>UPDATE</>'s <literal>SET</> list.
       information_schema now also shows this information.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <literal>WHEN</> clause to <link
       linkend="SQL-CREATETRIGGER"><command>CREATE TRIGGER</></link>
       to allow control over whether a trigger is fired (Takahiro
       Itagaki)
      </para>

      <para>
       While a check can be performed inside the trigger, doing it in an
       external <literal>WHEN</> clause has performance benefits.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

   <itemizedlist>

    <listitem>
     <para>
      Add the <literal>OR REPLACE</> clause to <link
      linkend="SQL-CREATELANGUAGE"><command>CREATE LANGUAGE</></link>
      (Tom Lane)
     </para>

     <para>
      This is helpful to optionally install a language if it does not
      already exist, and is particularly helpful now that PL/pgSQL is
      installed by default.
     </para>
    </listitem>

    </itemizedlist>

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

    <itemizedlist>

     <listitem>
      <para>
       Install PL/pgSQL by default (Bruce Momjian)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve PL/pgSQL's ability to handle row types with dropped columns
       (Pavel Stehule)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow input parameters to be assigned values within
       PL/pgSQL functions (Steve Prentice)
      </para>

      <para>
       Formerly, input parameters were treated as being declared
       <literal>CONST</>.  This restriction has been removed to simplify
       porting of functions from other DBMSes that do not impose the
       equivalent restriction.  An input parameter now acts like a local
       variable initialized to the passed-in value.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve error location reporting in PL/pgSQL (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Make PL/pgSQL use the main lexer, rather than its own version
       (Tom Lane)
      </para>

      <para>
       This ensures accurate tracking of the main system's behavior for details
       such as string escaping.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <replaceable>count</> and <literal>ALL</> options to <command>MOVE
       FORWARD</>/<literal>BACKWARD</> in PL/pgSQL (Pavel Stehule)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow PL/pgSQL's <literal>WHERE CURRENT OF</> to use a cursor
       variable (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow PL/pgSQL's <command>OPEN <replaceable>cursor</> FOR EXECUTE</> to
       use parameters (Pavel Stehule, Itagaki Takahiro)
      </para>

      <para>
       This is accomplished with a new <literal>USING</> clause.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add new PL/Perl functions: <link
       linkend="plperl-utility-functions"><function>quote_literal()</></link>,
       <function>quote_nullable()</>, <function>quote_ident()</>,
       <function>encode_bytea()</>, <function>decode_bytea()</>,
       <function>looks_like_number()</>,
       <function>encode_array_literal()</>,
       <function>encode_array_constructor()</> (Tim Bunce)
      </para>
     </listitem>

     <listitem>
      <para>
       Add server variable <link
       linkend="guc-plperl-on-init"><varname>plperl.on_init</></link> to
       specify a PL/Perl Perl initialization function (Tim
       Bunce)
      </para>

      <para>
       <link
       linkend="guc-plperl-on-plperl-init"><varname>plperl.on_plperl_init</></link>
       and <varname>plperl.on_plperlu_init</> are also available
       for trusted/untrusted-specific initialization.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve error context support in PL/Perl (Alexey Klyukin)
      </para>
     </listitem>

     <listitem>
      <para>
       Support <command>END</> blocks in PL/Perl (Tim Bunce)
      </para>

      <para>
       <command>END</> blocks do not currently allow database access.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <command>use strict</> in PL/Perl (Tim Bunce)
      </para>

      <para>
       This can be globally enabled with the server variable <link
       linkend="guc-plperl-use-strict"><varname>plperl.use_strict</></link>.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <command>require</> in PL/Perl (Tim Bunce)
      </para>

      <para>
       This basically tests to see if the module is loaded, and if not,
       generates an error.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <command>use feature</> in PL/Perl if Perl version 5.10 or
       later is used (Tim Bunce)
      </para>
     </listitem>

     <listitem>
      <para>
       Verify that PL/Perl return values are valid in the server encoding
       (Andrew Dunstan)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve PL/Perl code structure (Tim Bunce)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add Unicode support in PL/Python (Peter Eisentraut)
      </para>

      <para>
       Strings are automatically converted from/to the server encoding as
       necessary.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve <type>bytea</> support in PL/Python (Caleb Welton)
      </para>

      <para>
       <type>Bytea</> values passed into PL/Python now are represented as
       binary, rather than the PostgreSQL <type>bytea</> text format. Null
       bytes are now also output properly from PL/Python. <type>boolean</>
       and <type>numeric</> value passing in PL/Python was also improved.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="plpython-arrays">array parameter/return
       support</link> to PL/Python (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve mapping of domains to Python base types in PL/Python (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Add <application>Python</> 3 support to PL/Python (Peter Eisentraut)
      </para>

      <para>
       The new server-side language is called <link
       linkend="plpython-python23"><literal>plpython3u</></link>.  This
       cannot be used in the same backend with the usual
       <application>Python</> 2 server-side language.
      </para>
     </listitem>

     <listitem>
      <para>
       Improve error location and exception reporting in PL/Python (Peter Eisentraut)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

    <listitem>
    <para>
     Add <link linkend="APP-VACUUMDB"><command>vacuumdb</></link>
     <option>--analyze-only</> option to only analyze (Bruce Momjian)
     </para>
    </listitem>

   </itemizedlist>

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

     <listitem>
      <para>
       Properly escape <application>psql</> <link
       linkend="APP-PSQL-variables">variables</link> and
       identifiers (Pavel Stehule, Robert Haas)
      </para>

      <para>
       For example, <literal>:'var'</> will be escaped as a literal string, and
       <literal>:"var"</> will be escaped as an SQL identifier.
      </para>
     </listitem>

     <listitem>
      <para>
       Ignore leading UTF-8-encoded Unicode byte-order marker in
       <application>psql</> (Itagaki Takahiro)
      </para>

      <para>
       This is enabled when the client encoding is <acronym>UTF-8</>.
      </para>
     </listitem>

     <listitem>
      <para>
       Fix <command>psql --file -</> to properly honor <link
       linkend="R1-APP-PSQL-3"><option>--single-transaction</></link>
       (Bruce Momjian)
      </para>
     </listitem>

     <listitem>
      <para>
       Prevent overwriting of <application>psql</>'s command-line history
       if two <application>psql</> sessions are run simultaneously (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Improve <application>psql</>'s tab completion support (Itagaki
       Takahiro)
      </para>
     </listitem>

     <listitem>
      <para>
       Show <literal>\timing</> output when enabled, regardless of
       <quote>quiet</> mode (Peter Eisentraut)
      </para>
     </listitem>

    </itemizedlist>

    <sect5>
    <title><application>psql</> Display</title>
     <itemizedlist>

      <listitem>
       <para>
        Allow <application>psql</> to use fancy Unicode line-drawing
        characters via <command>\pset linestyle unicode</> (Roger Leigh)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve display of wrapped columns in <application>psql</> (Roger
        Leigh)
       </para>

       <para>
        The previous format is available by using <command>\pset linestyle
        old-ascii</>.
       </para>
      </listitem>

     </itemizedlist>

    </sect5>

    <sect5>
     <title><application>psql</> <link
     linkend="APP-PSQL-meta-commands"><command>\d</></link>
     Commands</title>
     <itemizedlist>

      <listitem>
       <para>
        Have <command>\d</> show child tables that inherit from the specified
        parent (Damien Clochard)
       </para>

       <para>
        <command>\d</> shows only the number of child tables, while
        <command>\d+</> shows the names of all child tables.
       </para>
      </listitem>

      <listitem>
       <para>
        Show definition of indexes in <command>\d index_name</> (Khee Chin)
       </para>

       <para>
        The definition is useful for expression indexes.
       </para>
      </listitem>

      <listitem>
       <para>
        In <application>psql</>, show the view definition only with <command>\d+</>,
        not with <command>\d</> (Peter Eisentraut)
       </para>
      </listitem>

     </itemizedlist>

    </sect5>
   </sect4>

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

     <listitem>
      <para>
       Have <application>pg_dump</>/<application>pg_restore</>
       <link linkend="pg-dump-options"><option>--clean</></link>
       also remove large objects (Itagaki Takahiro)
      </para>
     </listitem>

     <listitem>
      <para>
       Fix <application>pg_dump</> to properly dump large objects if
       standard_conforming_strings is enabled (Tom Lane)
      </para>

      <para>
       Large objects dumps now use hex format for output. (SWITCH DEFAULT
       FOR BETA? TOM)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <application>pg_dump</> to dump comments attached to columns
       of composite types (Taro Minowa (Higepon))
      </para>
     </listitem>

     <listitem>
      <para>
       Have <application>pg_dump</> <link
       linkend="pg-dump-options"><option>--verbose</></link>
       output the <application>pg_dump</> and server versions
       in text output mode (Jim Cox, Tom Lane)
      </para>

      <para>
       These were already present in custom output mode.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title><link
    linkend="app-pg-ctl"><application>pg_ctl</></link></title>
    <itemizedlist>

     <listitem>
      <para>
       Allow <application>pg_ctl</> to be safely used to start the
       <application>postmaster</> at boot-time (Tom Lane)
      </para>

      <para>
       Previously the <application>pg_ctl</> process could have been mistakenly
       identified as a running <application>postmaster</> based on a stale
       <application>postmaster</> lock file.
      </para>
     </listitem>

     <listitem>
      <para>
       Give <application>pg_ctl</> the ability to initialize the database
       (like <application>initdb</>) (Zdenek Kotala)
      </para>
     </listitem>


    </itemizedlist>

   </sect4>

  </sect3>

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

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

    <itemizedlist>

     <listitem>
      <para>
       Add new <application>libpq</> functions
       <link
       linkend="libpq-connect"><function>PQconnectdbParams()</></link>
       and <function>PQconnectStartParams()</> (Guillaume
       Lelarge)
      </para>

      <para>
       These functions are similar to <function>PQconnectdb()</> and
       <function>PQconnectStart()</> except they allow a null-terminated
       array of connection options, rather than requiring all options to
       be sent in a single string.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <application>libpq</> functions <link
       linkend="libpq-exec-escape-string"><function>PQescapeLiteral()</></link>
       and <function>PQescapeIdentifier()</> (Robert Haas)
      </para>

      <para>
       These functions return appropriately quoted and escaped literal
       strings and identifiers. The caller is not required to pre-allocate
       the string result, as is required by <function>PQescapeStringConn()</>.
      </para>
     </listitem>

     <listitem>
      <para>
       Add checking for a per-user service file (<link
       linkend="libpq-pgservice"><filename>.pg_service.conf</></link>),
       which is checked before the site-wide service file
       (Peter Eisentraut)
      </para>

      <para>
       The file <filename>.pg_service.conf</> is assumed to be in the
       user's home directory.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="libpq-keepalives">keepalive settings</link>
       in libpq (Tollef Fog Heen, Fujii Masao, Robert Haas)
      </para>

      <para>
       Keepalive settings were already supported on the server end of
       TCP connections.
      </para>
     </listitem>

     <listitem>
      <para>
       Properly report an error if the specified <application>libpq</> service
       cannot be found (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Issue a warning if the <link
       linkend="libpq-pgpass"><filename>.pgpass</></link>-retrieved
       password fails (Bruce Momjian)
      </para>
     </listitem>

     <listitem>
      <para>
       Load SSL certificate chains (Tom Lane)
      </para>

      <para>
       This improves handling of indirectly-signed SSL client
       certificates.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add <link linkend="ecpg-descriptors"><acronym>SQLDA</></link>
       (SQL Descriptor Area) support to <application>ecpg</>
       (Boszormenyi Zoltan)
      </para>
     </listitem>

     <listitem>
      <para>
       Add the <link linkend="ecpg-descriptors"><command>DESCRIBE</>
       [<literal>OUTPUT</>]</link> statement to <application>ecpg</>
       (Boszormenyi Zoltan)
      </para>
     </listitem>

     <listitem>
      <para>
       Add an <application>ecpg</> <link
       linkend="ecpg-library">function</link> to return the
       current transaction status (Bernd Helmle)
      </para>
     </listitem>

     <listitem>
      <para>
       Add the <literal>string</> data type in <application>ecpg</>
       Informix-compatibility mode (Boszormenyi Zoltan)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <application>ecpg</> to use <literal>new</> and <literal>old</>
       variable names without restriction (Michael Meskes)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow <application>ecpg</> to use variable names in
       <function>free()</>(Michael Meskes)
      </para>
     </listitem>

     <listitem>
      <para>
       Have <application>ecpg</> return zero for non-SQL3 data types
       (Michael Meskes))
      </para>

      <para>
       Previously it returned the negative of the data type <type>oid</>.
      </para>
     </listitem>

     <listitem>
      <para>
       Support <type>long long</> types on platforms that already have 64-bit
       <type>long</>s (Michael Meskes))
      </para>
     </listitem>

     </itemizedlist>

     <sect5>
      <title><application>ecpg</> Cursors</title>
      <itemizedlist>

      <listitem>
       <para>
        Add <application>ecpg</> out-of-scope cursor support in native mode
        (Boszormenyi Zoltan)
       </para>

       <para>
        This allows <command>DECLARE</> to use variables that are not in
        scope when <command>OPEN</> is called. This facility already existed
        in <application>ecpg</> Informix-compatibility mode.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow dynamic <application>ecpg</> cursor names (Boszormenyi Zoltan)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <application>ecpg</> to use noise words <literal>FROM</> and
        <literal>IN</> in <command>FETCH</> and <command>MOVE</> (Boszormenyi
        Zoltan)
       </para>
      </listitem>

     </itemizedlist>

    </sect5>

   </sect4>

  </sect3>

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

    <listitem>
     <para>
      Enable client thread safety by default (Bruce Momjian)
     </para>

     <para>
      Thread-safe builds can be disabled with <link
      linkend="configure"><application>configure</></link>
      <option>--disable-thread-safety</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Add a compile-time option to allow the Linux out-of-memory killer
      to kill backends (Alex Hunsaker, Tom Lane)
     </para>

     <para>
      Now that <filename>/proc/self/oom_adj</> allows disabling
      of the <productname>Linux</> out-of-memory (<acronym>OOM</>)
      killer for the postmaster and its children, the new
      compile-time option <link
      linkend="linux-memory-overcommit"><literal>-DLINUX_OOM_ADJ=0</></link>
      allows the killer to be enabled for <application>postmaster</>
      children. <application>pg_config</> shows if this flag
      was used during compilation.
     </para>
    </listitem>

    <listitem>
     <para>
      Use <productname>DocBook</> <acronym>XSL</> stylesheets for man page
      building (Peter Eisentraut)
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title>Makefiles</title>
    <itemizedlist>

     <listitem>
      <para>
       New <filename>Makefile</> targets <link
       linkend="build"><literal>world</></link>,
       <literal>install-world</>, and <literal>installcheck-world</>
       (Andrew Dunstan)
      </para>

      <para>
       These are similar to the existing <literal>all</>, <literal>install</>,
       and <literal>installcheck</> targets, but they build <acronym>HTML</>
       documentation, build and test <filename>contrib</>, and test
       server-side languages and <application>ecpg</>.
      </para>
     </listitem>

     <listitem>
      <para>
       Add data and documentation location control to <link
       linkend="xfunc-c-pgxs"><acronym>PGXS</></link> Makefiles
       (Mark Cave-Ayland)
      </para>
     </listitem>

     <listitem>
      <para>
       Restructure the <acronym>HTML</> documentation build
       <filename>Makefile</> rules (Peter Eisentraut)
      </para>
     </listitem>

    <listitem>
     <para>
      Add a Makefile rule to build documentation as a single text file
      (Bruce Momjian)
     </para>
    </listitem>

    <listitem>
     <para>
      Restructure use of <literal>LDFLAGS</> to be more consistent
      across platforms (Tom Lane)
     </para>
    </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>New Requirements</title>
    <itemizedlist>

     <listitem>
      <para>
       Require <application>Autoconf</> 2.63 for building from source (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
      <para>
       Require <application>Flex</> 2.5.31 or later to build from source
       (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Require <application>Perl</> version 5.8 or greater to build the server
       from a <acronym>CVS</> copy (John Naylor, Andrew Dunstan)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Windows</title>
    <itemizedlist>

     <listitem>
      <para>
       Add support for compiling on <link
       linkend="install-win32-full">64-bit
       <productname>Windows</></link> and running in 64-bit
       mode (Tsutomu Yamada, Magnus)
      </para>

      <para>
       This allows for large shared memory sizes on <productname>Windows</>.
      </para>
     </listitem>

     <listitem>
      <para>
       Allow server builds using <link
       linkend="install-win32-full"><productname>Visual Studio
       2008</></link> (Magnus Hagander)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow multiprocessor compilation using <productname>Microsoft Visual
       C</> (Magnus Hagander)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

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

    <listitem>
     <para>
      Distribute documentation in a proper directory tree, rather than
      as tar archive files inside the main distribution tarball (Peter Eisentraut)
     </para>

     <para>
      For example, the <acronym>HTML</> documentation is now in
      <filename>doc/src/sgml/html</>; the manual pages are packaged
      similarly.
     </para>
    </listitem>

    <listitem>
     <para>
      Enable the server's lexer to be reentrant (Tom Lane)
     </para>

     <para>
      This was needed for use of the lexer by PL/pgSQL.
     </para>
    </listitem>

    <listitem>
     <para>
      Improve speed of memory allocation (Tom Lane, Greg Stark)
     </para>
    </listitem>

    <listitem>
     <para>
      Add system columns to better document the use of indexes for constraint
      enforcement (Tom Lane)
     </para>
    </listitem>

    <listitem>
     <para>
      Allow multiple actions to be communicated using the same operating
      system signal (Fujii Masao)
     </para>

     <para>
      This allows improved backend communication as new features are
      added.
     </para>
    </listitem>

    <listitem>
     <para>
      Improve source code test coverage, including <filename>contrib</>, PL/Python,
      and PL/Perl (Peter Eisentraut, Andrew Dunstan)
     </para>
    </listitem>

    <listitem>
     <para>
      Remove the use of flat files for system table bootstrapping
      (Tom Lane, Alvaro Herrera)
     </para>

     <para>
      This also improves performance when using millions of users and
      databases.
     </para>
    </listitem>

    <listitem>
     <para>
      Improve the ability to translate <application>psql</> strings
      (Peter Eisentraut)
     </para>
    </listitem>

    <listitem>
     <para>
      Reduce the length of some file names so file paths are less than
      100 characters (Tom Lane)
     </para>

     <para>
      Some decompression programs have problems with long file names.
     </para>
    </listitem>

    <listitem>
     <para>
      Tighten input requirements for <type>int2</> vector input (Caleb
      Welton)
     </para>
    </listitem>

    <listitem>
     <para>
      Add a new <link
      linkend="errcodes-table"><literal>ERRCODE_INVALID_PASSWORD</></link>
      <literal>SQLSTATE</> error code (Bruce Momjian)
     </para>
    </listitem>

    <listitem>
     <para>
      Properly remove the few remaining personal source code copyright
      entries (Bruce Momjian)
     </para>

     <para>
      The personal copyright notices were insignificant but the community
      occasionally had to answer questions about them.
     </para>
    </listitem>

    <listitem>
     <para>
      New documentation <link linkend="non-durability">section</link>
      about running <productname>PostgreSQL</> in non-durable mode,
      to improve performance  (Bruce Momjian)
     </para>
    </listitem>

   </itemizedlist>

   <sect4>
    <title>Feature Support</title>
    <itemizedlist>

     <listitem>
      <para>
       Use a more modern <acronym>API</> for <application>Bonjour</> (Tom Lane)
      </para>

      <para>
       Bonjour now requires <productname>OS X</> 10.3 or later.
      </para>
     </listitem>

     <listitem>
      <para>
       Add processor test-and-test lock support for the <productname>SuperH</>
       architecture (Nobuhiro Iwamatsu)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow non-<application>GCC</> compilers to use inline functions if
       they support them (Kurt Harriman)
      </para>
     </listitem>

     <listitem>
      <para>
       Remove support for platforms that don't have a working 64-bit
       integer data types (Tom Lane)
      </para>

      <para>
       It is believed all supported platforms have working 64-bit integer
       data types.
      </para>
     </listitem>


    </itemizedlist>

   </sect4>

   <sect4>
    <title>Server Programming</title>
    <itemizedlist>

     <listitem>
      <para>
       Simplify use of <productname>C++</> functions in backend code (Kurt
       Harriman, Peter Eisentraut)
      </para>

      <para>
       While this removes keyword conflicts that previously made
       <productname>C++</> usage difficult in backend code, there are
       still other complexities when using <productname>C++</> for backend
       functions. <literal>extern "C" { }</> is still necessary in
       appropriate places.
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link
       linkend="xaggr"><function>AggCheckCallContext()</></link>
       for use in detecting if a <productname>C</> function is
       being called as an aggregate (Hitoshi Harada)
      </para>
     </listitem>

     <listitem>
      <para>
       Require <function>fastgetattr()</> and <function>heap_getattr()</>
       backend macros to use a non-NULL fourth argument (Robert Haas)
       KEEP?
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

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

     <listitem>
      <para>
       Add parser hooks to access column and parameter references in
       queries (Tom Lane)
      </para>
     </listitem>

     <listitem>
      <para>
       Add a hook so loadable modules can control utility commands (Itagaki
       Takahiro)
      </para>
     </listitem>

     <listitem>
      <para>
       Allow the calling of parser hooks from <acronym>SPI</> and cached
       plans (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

   <sect4>
    <title>Binary Upgrade Support</title>
    <itemizedlist>

    <listitem>
     <para>
      Add <link linkend="pgupgrade"><filename>contrib/pg_upgrade</></link>
      to support in-place upgrades (Bruce Momjian)
     </para>

     <para>
      This avoids the requirement of dumping/reloading the database when
      upgrading to a new major release of PostgreSQL and speeds up offline
      upgrades by orders of magnitude. It supports upgrades to 9.0
      from PostgreSQL 8.3 and 8.4.
     </para>
    </listitem>

     <listitem>
      <para>
       Add support for preservation of all <link
       linkend="catalog-pg-class"><structname>relfilenodes</></link>,
       for use during binary upgrades (Bruce Momjian)
      </para>
     </listitem>

     <listitem>
      <para>
       Add support for binary upgrades to preserve <structname>pg_type</>
       and <structname>pg_enum</> <type>oids</> (Bruce Momjian)
      </para>

      <para>
       This is needed to allow binary upgrades of user-defined composite
       types, arrays, and enums (enumerated types).
      </para>
     </listitem>

     <listitem>
      <para>
       Move tablespace data directories into their own
       <productname>PostgreSQL</> version-specific subdirectory (Bruce Momjian)
      </para>

      <para>
       This simplifies binary upgrades.
      </para>
     </listitem>

    </itemizedlist>

   </sect4>

  </sect3>

  <sect3>
   <title>Contrib</title>
   <itemizedlist>

    <listitem>
     <para>
      Add multithreaded option (<option>-j</>) to <link
      linkend="pgbench"><filename>contrib/pgbench</></link>
      (Itagaki Takahiro)
     </para>

     <para>
      This allows multiple <acronym>CPU</>s to be used for pgbench tests.
     </para>
    </listitem>

    <listitem>
     <para>
      Add <command>\shell</> and <command>\setshell</> meta
      commands to <link
      linkend="pgbench"><filename>contrib/pgbench</></link>
      (Michael Paquier)
     </para>
    </listitem>

    <listitem>
     <para>
      New features for <link
      linkend="dict-xsyn"><filename>contrib/dict_xsyn</></link>
      (Sergey Karpov)
     </para>

     <para>
      The new options are <literal>matchorig</>, <literal>matchsynonyms</>,
      and <literal>keepsynonyms</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Add full text dictionary <link
      linkend="unaccent"><filename>contrib/unaccent</></link>
      (Teodor Sigaev)
     </para>

     <para>
      This filter dictionary removes accents from letters, which
      makes full-text searches over multiple languages much easier.
     </para>
    </listitem>

    <listitem>
     <para>
      Add <link
      linkend="CONTRIB-DBLINK-GET-NOTIFY"><function>dblink_get_notify()</></link>
      to <filename>contrib/dblink</> (Marcus Kempe)
     </para>

     <para>
      This allows asynchronous notifications in <productname>dblink</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Improve <filename>contrib/dblink</>s handling of dropped columns
      (Tom Lane)
     </para>

     <para>
      This affects <link
      linkend="CONTRIB-DBLINK-BUILD-SQL-INSERT"><function>dblink_build_sql_insert()</></link>
      and related functions.
     </para>
    </listitem>

    <listitem>
     <para>
      Greatly increase <link
      linkend="hstore"><filename>contrib/hstore</></link>'s
      length limit and add B-tree and hash abilities so <literal>GROUP
      BY</> and <literal>DISTINCT</> operations are possible
      (Andrew Gierth)
     </para>

     <para>
      New functions and operators were also added.  These improvements
      make hstore a full-functional key-value store embedded in PostgreSQL.
     </para>
    </listitem>

    <listitem>
     <para>
      Add <link
      linkend="passwordcheck"><filename>contrib/passwordcheck</></link>
      which can check the strength of assigned passwords (Laurenz
      Albe)
     </para>

     <para>
      The source code of this module should be modified to implement
      site-specific password policies.
     </para>
    </listitem>

    <listitem>
     <para>
      Add <link
      linkend="pgarchivecleanup"><filename>contrib/pg_archivecleanup</></link>
      tool (Simon Riggs)
     </para>

     <para>
      This is designed to be used by the <literal>archive_cleanup_command</literal>
      setting to remove unnecessary archive files.
     </para>
    </listitem>

    <listitem>
     <para>
      Add query text to <link
      linkend="auto-explain"><filename>contrib/auto_explain</></link>
      output (Andrew Dunstan)
     </para>
    </listitem>

    <listitem>
     <para>
      Add buffer access counters to <link
      linkend="pgstatstatements"><filename>contrib/pg_stat_statements</></link>
      (Itagaki Takahiro)
     </para>
    </listitem>

    <listitem>
     <para>
      Update <link
      linkend="server-start"><filename>contrib/start-scripts/linux</></link>
      to use <filename>/proc/self/oom_adj</> to disable the
      <link linkend="linux-memory-overcommit"><productname>Linux</>
      out-of-memory</link> (<acronym>OOM</>) killer (Alex
      Hunsaker, Tom Lane)
     </para>
    </listitem>

   </itemizedlist>

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