<!-- doc/src/sgml/release-9.4.sgml -->
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 <sect1 id="release-9-4">
  <title>Release 9.4</title>

  <note>
   <title>Release Date</title>
   <simpara>2014-??-??</simpara>
   <simpara>Current as of 2014-11-17</simpara>
   <!-- Be sure to remove "delta from 9.4beta" items below before final! -->
  </note>

  <sect2>
   <title>Overview</title>

   <para>
    Major enhancements in <productname>PostgreSQL</> 9.4 include:
   </para>

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

   <itemizedlist>

     <listitem>
      <para>
       Allow <link linkend="rules-materializedviews">materialized views</>
       to be refreshed without blocking reads
      </para>
     </listitem>

     <listitem>
      <para>
       Add support for <link linkend="logicaldecoding">logical decoding</>
       of WAL data, to allow database changes to be streamed out in a
       customizable format
      </para>
     </listitem>

     <listitem>
      <para>
        Allow <link linkend="bgworker">background worker processes</>
        to be dynamically registered, started and terminated
      </para>
     </listitem>

     <listitem>
      <para>
       Add <link linkend="datatype-json"><type>jsonb</></link>, a more
       capable and efficient data type for storing <acronym>JSON</> data
      </para>
     </listitem>

     <listitem>
      <para>
       Add new <acronym>SQL</> command <xref linkend="SQL-ALTERSYSTEM">
       for updating <filename>postgresql.conf</> configuration file entries
      </para>
     </listitem>

     <listitem>
      <para>
       Reduce lock strength for some <xref linkend="SQL-ALTERTABLE">
       commands
      </para>
     </listitem>

   </itemizedlist>

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

  </sect2>

  <sect2>

  <title>Migration to Version 9.4</title>

   <para>
    A dump/restore using <xref linkend="app-pg-dumpall">, or use
    of <xref linkend="pgupgrade">, is required for those wishing to migrate
    data from any previous release.
   </para>

   <para>
    Version 9.4 contains a number of changes that may affect compatibility
    with previous releases.  Observe the following incompatibilities:
   </para>

   <itemizedlist>

    <!-- delta from 9.4beta2, be sure to remove before final: -->
    <listitem>
     <para>
      Change on-disk format of <type>jsonb</> data
      (Heikki Linnakangas and Tom Lane)
     </para>

     <para>
      The on-disk representation was changed after 9.4beta2 to improve
      efficiency.  <application>pg_upgrade</> will refuse to upgrade any
      9.4beta1 or 9.4beta2 database containing <type>jsonb</> columns; you
      will need to use <application>pg_dumpall</> instead to migrate such
      databases.
     </para>
    </listitem>

    <!-- delta from 9.4beta3, be sure to remove before final: -->
    <listitem>
     <para>
      Fix representation of numeric values in <type>jsonb</> GIN indexes
      (Tom Lane)
     </para>

     <para>
      Numeric items within <type>jsonb</> values are converted to strings
      for storage in GIN <literal>jsonb_ops</> indexes.  In 9.4beta3,
      trailing zeroes in such items were mishandled.  Beta testers
      should <command>REINDEX</> any such indexes after upgrading, to ensure
      that searches for numeric values will find the expected rows.  Note
      that <literal>jsonb_path_ops</> indexes were not affected by this bug.
     </para>
    </listitem>

    <listitem>
     <para>
      Tighten checks for multidimensional <link
      linkend="arrays">array</link> input (Bruce Momjian)
     </para>

     <para>
      Previously, an input array string that started with a single-element
      array dimension could later contain multidimensional segments,
      e.g. <literal>'{{1}, {2,3}}'::int[]</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Unicode escapes in <link linkend="datatype-json"><type>JSON</type></link>
      text values are no longer rendered with the backslash escaped
      (Andrew Dunstan)
     </para>

     <para>
      Previously, all backslashes in text values being formed into JSON
      were escaped. Now a backslash followed by <literal>u</> and four
      hexadecimal digits is not escaped, as this is a legal sequence in a
      JSON string value, and escaping the backslash led to some perverse
      results.
     </para>
    </listitem>

    <listitem>
     <para>
      When converting values of type <type>date</>, <type>timestamp</>
      or <type>timestamptz</>
      to <link linkend="datatype-json"><type>JSON</type></link>, render the
      values in a format compliant with ISO 8601 (Andrew Dunstan)
     </para>

     <para>
      Previously such values were rendered according to the current
      <xref linkend="guc-datestyle"> setting; but many JSON processors
      require timestamps to be in ISO 8601 format.  If necessary, the
      previous behavior can be obtained by explicitly casting the datetime
      value to <type>text</> before passing it to the JSON conversion
      function.
     </para>
    </listitem>

    <listitem>
     <para>
      The <link linkend="functions-json-op-table"><type>json</type>
      <literal>#&gt;</> <type>text[]</> path extraction operator</link> now
      returns its lefthand input, not NULL, if the array is empty (Tom Lane)
     </para>

     <para>
      This is consistent with the notion that this represents zero
      applications of the simple field/element extraction
      operator <literal>-&gt;</>.  Similarly, <type>json</type>
      <literal>#&gt;&gt;</> <type>text[]</> with an empty array merely
      coerces its lefthand input to text.
     </para>
    </listitem>

    <listitem>
     <para>
      Corner cases in
      the <link linkend="functions-json-op-table"><type>JSON</type>
      field/element/path extraction operators</link> now return NULL rather
      than raising an error (Tom Lane)
     </para>

     <para>
      For example, applying field extraction to a JSON array now yields NULL
      not an error.  This is more consistent (since some comparable cases such
      as no-such-field already returned NULL), and it makes it safe to create
      expression indexes that use these operators, since they will now not
      throw errors for any valid JSON input.
     </para>
    </listitem>

    <listitem>
     <para>
      Cause consecutive whitespace in <link
      linkend="functions-formatting-table"><function>to_timestamp()</></link>
      and <function>to_date()</> format strings to consume a corresponding
      number of characters in the input string (whitespace or not), then
      conditionally consume adjacent whitespace, if not in <literal>FX</>
      mode (Jeevan Chalke)
     </para>

     <para>
      Previously, consecutive whitespace characters in a non-<literal>FX</>
      format string behaved like a single whitespace character and consumed
      all adjacent whitespace in the input string.  For example, previously
      a format string of three spaces would consume only the first space in
      <literal>' 12'</>, but it will now consume all three characters.
     </para>
    </listitem>

    <listitem>
     <para>
      Fix <link
      linkend="textsearch-functions-table"><function>ts_rank_cd()</></link>
      to ignore stripped lexemes (Alex Hill)
     </para>

     <para>
      Previously, stripped lexemes were treated as if they had a default
      location, producing a rank of dubious usefulness.
     </para>
    </listitem>

    <listitem>
     <para>
      For functions declared to
      take <link linkend="xfunc-sql-variadic-functions"><literal>VARIADIC
      "any"</></link>, an actual parameter marked as <literal>VARIADIC</>
      must be of a determinable array type (Pavel Stehule)
     </para>

     <para>
      Such parameters can no longer be written as an undecorated string
      literal or <literal>NULL</>; a cast to an appropriate array data type
      will now be required.  Note that this does not affect parameters not
      marked <literal>VARIADIC</>.
     </para>
    </listitem>

    <listitem>
     <para>
      Ensure that whole-row variables expose the expected column names
      to functions that pay attention to column names within composite
      arguments (Tom Lane)
     </para>

     <para>
      Constructs like <literal>row_to_json(tab.*)</> now always emit column
      names that match the column aliases visible for table <literal>tab</>
      at the point of the call.  In previous releases the emitted column
      names would sometimes be the table's actual column names regardless
      of any aliases assigned in the query.
     </para>
    </listitem>

    <listitem>
     <para>
      <xref linkend="sql-discard"> now also discards sequence-related state
      (Fabr&iacute;zio de Royes Mello, Robert Haas)
     </para>
    </listitem>

    <listitem>
     <para>
      Rename <link linkend="SQL-EXPLAIN"><command>EXPLAIN
      ANALYZE</></link>'s <quote>total runtime</quote> output
      to <quote>execution time</quote> (Tom Lane)
     </para>

     <para>
      Now that planning time is also reported, the previous name was
      confusing.
     </para>
    </listitem>

    <listitem>
     <para>
      <link linkend="SQL-SHOW"><command>SHOW TIME ZONE</></link> now
      outputs simple numeric UTC offsets in <acronym>POSIX</> timezone
      format (Tom Lane)
     </para>

     <para>
      Previously, such timezone settings were displayed as <link
      linkend="datatype-interval-output"><type>interval</></link> values.
      The new output is properly interpreted by <command>SET TIME ZONE</>
      when passed as a simple string, whereas the old output required
      special treatment to be re-parsed correctly.
     </para>
    </listitem>

    <listitem>
     <para>
      Foreign data wrappers that support updating foreign tables must
      consider the possible presence of <literal>AFTER ROW</> triggers
      (Noah Misch)
     </para>

     <para>
      When an <literal>AFTER ROW</> trigger is present, all columns of the
      table must be returned by updating actions, since the trigger might
      inspect any or all of them.  Previously, foreign tables never had
      triggers, so the FDW might optimize away fetching columns not mentioned
      in the <literal>RETURNING</> clause (if any).
     </para>
    </listitem>

    <listitem>
     <para>
      Prevent <link
      linkend="ddl-constraints-check-constraints"><literal>CHECK</></link>
      constraints from referencing system columns, except
      <structfield>tableoid</> (Amit Kapila)
     </para>

     <para>
      Previously such check constraints were allowed, but they would often
      cause errors during restores.
     </para>
    </listitem>

    <listitem>
     <para>
      Use the last specified <xref linkend="recovery-target"> if multiple
      values are specified (Heikki Linnakangas)
     </para>
    </listitem>

    <listitem>
     <para>
      On Windows, automatically preserve quotes in command strings supplied
      by the user (Heikki Linnakangas)
     </para>

     <para>
      User commands that did their own quote preservation might need
      adjustment.  This is likely to be an issue for commands used in
      <xref linkend="guc-archive-command">, <xref linkend="restore-command">,
      and <link linkend="sql-copy"><command>COPY TO/FROM PROGRAM</></link>.
     </para>
    </listitem>

    <listitem>
     <para>
      Remove catalog column <link
      linkend="catalog-pg-class"><structfield>pg_class.reltoastidxid</></link>
      (Michael Paquier)
     </para>
    </listitem>

    <listitem>
     <para>
      Remove catalog column <link
      linkend="catalog-pg-rewrite"><structfield>pg_rewrite.ev_attr</></link>
      (Kevin Grittner)
     </para>

     <para>
      Per-column rules have not been supported since
      <application>PostgreSQL</> 7.3.
     </para>
    </listitem>

    <listitem>
     <para>
      Remove native support for <application>Kerberos</> authentication
      (<option>--with-krb5</>, etc)
      (Magnus Hagander)
     </para>

     <para>
      The supported way to use <application>Kerberos</> authentication is
      with <acronym>GSSAPI</>.  The native code has been deprecated since
      <productname>PostgreSQL</> 8.3.
     </para>
    </listitem>

    <listitem>
     <para>
      In <application>PL/Python</>, handle domains over arrays like the
      underlying array type (Rodolfo Campero)
     </para>

     <para>
      Previously such values were treated as strings.
     </para>
    </listitem>

    <listitem>
     <para>
      Make libpq's <link
      linkend="libpq-pqconnectdbparams"><function>PQconnectdbParams()</></link>
      and <link
      linkend="libpq-pqpingparams"><function>PQpingParams()</></link>
      functions process zero-length strings as defaults (Adrian
      Vondendriesch)
     </para>

     <para>
      Previously, these functions treated zero-length string values as
      selecting the default in only some cases.
     </para>
    </listitem>

    <listitem>
     <para>
      Change empty arrays returned by the <xref linkend="intarray"> module
      to be zero-dimensional arrays (Bruce Momjian)
     </para>

     <para>
      Previously, empty arrays were returned as zero-length one-dimensional
      arrays, whose text representation looked the same as zero-dimensional
      arrays (<literal>{}</>), but they acted differently in array
      operations.  <application>intarray</>'s behavior in this area now
      matches the built-in array operators.
     </para>
    </listitem>

    <listitem>
     <para>
      <xref linkend="pgupgrade"> now uses <option>-U</>
      or <option>--username</> to specify the user name (Bruce Momjian)
     </para>

     <para>
      Previously this option was spelled <option>-u</> or <option>--user</>,
      but that was inconsistent with other tools.
     </para>
    </listitem>

    <!-- delta from 9.4beta2, be sure to remove before final: -->
    <listitem>
     <para>
      Update time zone data files to tzdata release 2014j for DST law
      changes in Russia and elsewhere
     </para>

     <para>
      This change is more significant than most time zone updates because
      many Russian zone abbreviations are changing meaning, including IRKT,
      KRAT, MAGT, MSK, NOVT, OMST, SAKT, VLAT, YAKT, and YEKT.
      <productname>PostgreSQL</> will now associate the correct UTC offset
      with these abbreviations depending on the given date.  Also, IANA
      has formally recognized abbreviations of the form
      A<replaceable>x</>ST/A<replaceable>x</>DT for Australian timezones,
      so adopt those names as part of the <quote>Default</> abbreviation
      set in <productname>PostgreSQL</>.  The <quote>Australia</>
      abbreviation set now need be selected only if it's desired to use
      historical abbreviations that conflict with abbreviations commonly
      used elsewhere, such as EST or SAST.
     </para>
    </listitem>

   </itemizedlist>

  </sect2>

  <sect2>
   <title>Changes</title>

   <para>
    Below you will find a detailed account of the changes between
    <productname>PostgreSQL</productname> 9.4 and the previous major
    release.
   </para>

   <sect3>
    <title>Server</title>

     <itemizedlist>

      <listitem>
       <para>
        Allow <link linkend="bgworker">background worker processes</link>
        to be dynamically registered, started and terminated (Robert Haas)
       </para>

       <para>
        The <filename>contrib/worker_spi</> module shows an example of use
        of this feature.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow dynamic allocation of shared memory segments (Robert Haas,
        Amit Kapila)
       </para>

       <para>
        This feature is illustrated in <filename>contrib/test_shm_mq</filename>.
       </para>
      </listitem>

      <listitem>
       <para>
        During crash recovery or immediate shutdown, send uncatchable
        termination signals (<systemitem>SIGKILL</>) to child processes
        that do not shut down promptly (MauMau, &Aacute;lvaro Herrera)
       </para>

       <para>
        This reduces the likelihood of leaving orphaned child processes
        behind after <xref linkend="app-postmaster"> shutdown, as well
        as ensuring that crash recovery can proceed if some child processes
        have become <quote>stuck</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve randomness of the database system identifier (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="SQL-VACUUM"> properly report dead but
        not-yet-removable rows to the statistics collector (Hari Babu)
       </para>

       <para>
        Previously these were reported as live rows.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>Indexes</title>

     <itemizedlist>

      <listitem>
       <para>
        Reduce <link linkend="GIN"><acronym>GIN</></link> index size
        (Alexander Korotkov, Heikki Linnakangas)
       </para>

       <para>
        Indexes upgraded via <xref linkend="pgupgrade"> will work fine
        but will still be in the old, larger <acronym>GIN</> format.
        Use <xref linkend="SQL-REINDEX"> to recreate such an index in the
        new format.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve speed of multi-key <link
        linkend="GIN"><acronym>GIN</></link> lookups (Alexander Korotkov,
        Heikki Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="GiST"><acronym>GiST</></link> index support
        for <link linkend="datatype-inet"><type>inet</></link> and
        <link linkend="datatype-cidr"><type>cidr</></link> data types
        (Emre Hasegeli)
       </para>

       <para>
        Such indexes improve <link
        linkend="cidr-inet-operators-table">subnet and supernet</link>
        lookups and ordering comparisons.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix rare race condition in B-tree page deletion (Heikki Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Make the handling of interrupted B-tree page splits more robust
        (Heikki Linnakangas)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>General Performance</title>

     <itemizedlist>

      <listitem>
       <para>
        Allow multiple backends to insert
        into <link linkend="wal"><acronym>WAL</></link> buffers
        concurrently (Heikki Linnakangas)
       </para>

       <para>
        This improves parallel write performance.
       </para>
      </listitem>

      <listitem>
       <para>
        Conditionally write only the modified portion of updated rows to
        <link linkend="wal"><acronym>WAL</></link> (Amit Kapila)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve performance of aggregate functions used as <link
        linkend="syntax-window-functions">window functions</link>
        (David Rowley, Florian Pflug, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve speed of aggregates that
        use <link linkend="datatype-numeric"><type>numeric</></link> state
        values (Hadi Moshayedi)
       </para>
      </listitem>

      <listitem>
       <para>
        Attempt to <link linkend="vacuum-for-wraparound">freeze</link>
        tuples when tables are rewritten with <xref
        linkend="SQL-CLUSTER"> or <link
        linkend="SQL-VACUUM"><command>VACUUM FULL</></link> (Robert Haas,
        Andres Freund)
       </para>

       <para>
        This can avoid the need to freeze the tuples in the future.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve speed of <xref linkend="SQL-COPY">
        with <literal>DEFAULT</> <link
        linkend="functions-sequence-table"><function>nextval()</></link>
        columns (Simon Riggs)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve speed of accessing many different <link
        linkend="SQL-CREATESEQUENCE">sequences</link> in the same session
        (David Rowley)
       </para>
      </listitem>

      <listitem>
       <para>
        Raise hard limit on the number of tuples held in memory during sorting
        and B-tree index builds (Noah Misch)
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce memory allocated by <application>PL/pgSQL</>
        <xref linkend="SQL-DO"> blocks (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Make the planner more aggressive in extracting restriction clauses
        from mixed <literal>AND</>/<literal>OR</> clauses (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Disallow pushing volatile <literal>WHERE</> clauses down
        into <literal>DISTINCT</> subqueries (Tom Lane)
       </para>

       <para>
        Pushing down a <literal>WHERE</> clause can produce a more
        efficient plan overall, but at the cost of evaluating the clause
        more often than is implied by the text of the query; so don't do it
        if the clause contains any volatile functions.
       </para>
      </listitem>

      <listitem>
       <para>
        Auto-resize the catalog caches (Heikki Linnakangas)
       </para>

       <para>
        This reduces memory consumption for sessions accessing only a few
        tables, and improves performance for sessions accessing many tables.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Monitoring</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <xref linkend="pg-stat-archiver-view"> system view to
        report <link linkend="wal"><acronym>WAL</></link> archiver activity
        (Gabriele Bartolini)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <structfield>n_mod_since_analyze</> columns to
        <xref linkend="pg-stat-all-tables-view"> and related system views
        (Mark Kirkwood)
       </para>

       <para>
        These columns expose the system's estimate of the number of changed
        tuples since the table's last <xref linkend="sql-analyze">.  This
        estimate drives decisions about when to auto-analyze.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <structfield>backend_xid</> and <structfield>backend_xmin</>
        columns to the system view <xref linkend="pg-stat-activity-view">,
        and a <structfield>backend_xmin</> column to
        <xref linkend="pg-stat-replication-view"> (Christian Kruse)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><acronym>SSL</></title>

     <itemizedlist>

      <listitem>
       <para>
        Add support for <acronym>SSL</> <acronym>ECDH</> key exchange
        (Marko Kreen)
       </para>

       <para>
        This allows use of Elliptic Curve keys for server authentication.
        Such keys are faster and have better security than <acronym>RSA</>
        keys. The new configuration parameter
        <xref linkend="guc-ssl-ecdh-curve">
        controls which curve is used for <acronym>ECDH</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve the default <xref linkend="guc-ssl-ciphers"> setting
        (Marko Kreen)
       </para>
      </listitem>

      <listitem>
       <para>
        By default, the server not the client now controls the preference
        order of <acronym>SSL</> ciphers
        (Marko Kreen)
       </para>

       <para>
        Previously, the order specified by <xref linkend="guc-ssl-ciphers">
        was usually ignored in favor of client-side defaults, which are not
        configurable in most <productname>PostgreSQL</> clients.  If
        desired, the old behavior can be restored via the new configuration
        parameter <xref linkend="guc-ssl-prefer-server-ciphers">.
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="guc-log-connections"> show <acronym>SSL</>
        encryption information (Andreas Kunert)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve <acronym>SSL</> renegotiation handling (&Aacute;lvaro
        Herrera)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

      <listitem>
       <para>
        Add new <acronym>SQL</> command <xref linkend="SQL-ALTERSYSTEM">
        for updating <filename>postgresql.conf</> configuration file entries
        (Amit Kapila)
       </para>

       <para>
        Previously such settings could only be changed by manually
        editing <filename>postgresql.conf</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="guc-autovacuum-work-mem"> configuration parameter
        to control the amount of memory used by autovacuum workers
        (Peter Geoghegan)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="guc-huge-pages"> parameter to allow using huge
        memory pages on Linux (Christian Kruse, Richard Poole, Abhijit
        Menon-Sen)
       </para>

       <para>
        This can improve performance on large-memory systems.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="guc-max-worker-processes"> parameter
        to limit the number of background workers (Robert Haas)
       </para>

       <para>
        This is helpful in configuring a standby server to have the
        required number of worker processes (the same as the primary).
       </para>
      </listitem>

      <listitem>
       <para>
        Add superuser-only <xref linkend="guc-session-preload-libraries">
        parameter to load libraries at session start (Peter Eisentraut)
       </para>

       <para>
        In contrast to <xref linkend="guc-local-preload-libraries">, this
        parameter can load any shared library, not just those in
        the <filename>$libdir/plugins</> directory.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="guc-wal-log-hints"> parameter to enable WAL
        logging of hint-bit changes (Sawada Masahiko)
       </para>

       <para>
        Hint bit changes are not normally logged, except when checksums are
        enabled.  This is useful for external tools
        like <application>pg_rewind</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Increase the default settings of <xref linkend="guc-work-mem">
        and <xref linkend="guc-maintenance-work-mem"> by four times (Bruce
        Momjian)
       </para>

       <para>
        The new defaults are 4MB and 64MB respectively.
       </para>
      </listitem>

      <listitem>
       <para>
        Increase the default setting of <xref
        linkend="guc-effective-cache-size">
        to 4GB (Bruce Momjian, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <function>printf</function>-style space padding to be
        specified in <xref linkend="guc-log-line-prefix"> (David Rowley)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow terabyte units (<literal>TB</>) to be used when specifying
        configuration variable values (Simon Riggs)
       </para>
      </listitem>

      <listitem>
       <para>
        Show <acronym>PID</>s of lock holders and waiters and improve
        information about relations in <xref linkend="guc-log-lock-waits">
        log messages (Christian Kruse)
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce server logging level when loading shared libraries (Peter
        Geoghegan)
       </para>

       <para>
        The previous level was <literal>LOG</>, which was too verbose
        for per-session libraries.
       </para>
      </listitem>

      <listitem>
       <para>
        On Windows, make <literal>SQL_ASCII</>-encoded databases and server
        processes (e.g., <xref linkend="app-postmaster">) emit messages in
        the character encoding of the server's Windows user locale
        (Alexander Law, Noah Misch)
       </para>

       <para>
        Previously these messages were output in the Windows
        <acronym>ANSI</> code page.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="streaming-replication-slots">replication
        slots</link> to coordinate activity on streaming standbys with the
        node they are streaming from (Andres Freund, Robert Haas)
       </para>

       <para>
        Replication slots allow preservation of resources like
        <acronym>WAL</> files on the primary until they are no longer
        needed by standby servers.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="recovery-config"><filename>recovery.conf</></link>
        parameter <xref linkend="recovery-min-apply-delay">
        to delay replication (Robert Haas, Fabr&iacute;zio de Royes Mello,
        Simon Riggs)
       </para>

       <para>
        Delaying replay on standby servers can be useful for recovering
        from user errors.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="recovery-target">
        option <option>immediate</> to stop <link
        linkend="wal"><acronym>WAL</></link> recovery as soon as a
        consistent state is reached (MauMau, Heikki Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve recovery target processing (Heikki Linnakangas)
       </para>

       <para>
        The timestamp reported
        by <link linkend="functions-recovery-info-table"><function>pg_last_xact_replay_timestamp()</></link>
        now reflects already-committed records, not transactions about to
        be committed. Recovering to a restore point now replays the restore
        point, rather than stopping just before the restore point.
       </para>
      </listitem>

      <listitem>
       <para>
        <link
        linkend="functions-admin-backup-table"><function>pg_switch_xlog()</></link>
        now clears any unused trailing space in the old <acronym>WAL</> file
        (Heikki Linnakangas)
       </para>

       <para>
        This improves the compression ratio for <acronym>WAL</> files.
       </para>
      </listitem>

      <listitem>
       <para>
        Report failure return codes from <link
        linkend="archive-recovery-settings">external recovery commands</>
        (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce spinlock contention during <acronym>WAL</> replay (Heikki
        Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Write <acronym>WAL</> records of running transactions more
        frequently (Andres Freund)
       </para>

       <para>
        This allows standby servers to start faster and clean up resources
        more aggressively.
       </para>
      </listitem>

     </itemizedlist>

     <sect4>
      <title><link linkend="logicaldecoding">Logical Decoding</></title>

      <para>
       Logical decoding allows database changes to be streamed in a
       configurable format. The data is read from
       the <link linkend="wal"><acronym>WAL</></link> and transformed into the
       desired target format. To implement this feature, the following changes
       were made:
      </para>

      <itemizedlist>

       <listitem>
        <para>
         Add support for <link linkend="logicaldecoding">logical decoding</>
         of WAL data, to allow database changes to be streamed out in a
         customizable format
         (Andres Freund)
        </para>
       </listitem>

       <listitem>
        <para>
         Add new <xref linkend="guc-wal-level"> setting <option>logical</>
         to enable logical change-set encoding in <acronym>WAL</> (Andres
         Freund)
        </para>
       </listitem>

       <listitem>
        <para>
         Add table-level parameter <link
         linkend="catalog-pg-class"><literal>REPLICA IDENTITY</></link>
         to control logical replication (Andres Freund)
        </para>
       </listitem>

       <listitem>
        <para>
         Add relation option <link
         linkend="SQL-CREATETABLE-storage-parameters"><option>user_catalog_table</></link>
         to identify user-created tables involved in logical change-set
         encoding (Andres Freund)
        </para>
       </listitem>

       <listitem>
        <para>
         Add <xref linkend="app-pgrecvlogical"> application to receive
         logical-decoding data (Andres Freund)
        </para>
       </listitem>

       <listitem>
        <para>
         Add <xref linkend="test-decoding"> module to illustrate logical
         decoding at the <acronym>SQL</> level (Andres Freund)
        </para>
       </listitem>

      </itemizedlist>

     </sect4>

   </sect3>

   <sect3>
    <title>Queries</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="queries-tablefunctions"><literal>WITH
        ORDINALITY</></link> syntax to number rows returned from
        set-returning functions in the <literal>FROM</> clause
        (Andrew Gierth, David Fetter)
       </para>

       <para>
        This is particularly useful for functions like
        <function>unnest()</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="queries-tablefunctions"><literal>ROWS
        FROM()</></link> syntax to allow horizontal concatenation of
        set-returning functions in the <literal>FROM</> clause (Andrew Gierth)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <xref linkend="SQL-SELECT"> to have
        an empty target list (Tom Lane)
       </para>

       <para>
        This was added so that views that select from a table with zero
        columns can be dumped and restored correctly.
       </para>
      </listitem>

      <listitem>
       <para>
        Ensure that <link linkend="SQL-SELECT"><literal>SELECT ... FOR UPDATE
        NOWAIT</></link> does not wait in corner cases involving
        already-concurrently-updated tuples (Craig Ringer and Thomas Munro)
       </para>
      </listitem>

     </itemizedlist>

   </sect3>

   <sect3>
    <title>Utility Commands</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link linkend="SQL-DISCARD"><command>DISCARD
        SEQUENCES</></link> command to discard cached sequence-related state
        (Fabr&iacute;zio de Royes Mello, Robert Haas)
       </para>

       <para>
        <command>DISCARD ALL</> will now also discard such information.
       </para>
      </listitem>

       <listitem>
        <para>
         Add <literal>FORCE NULL</> option
         to <link linkend="SQL-COPY"><command>COPY FROM</></link>, which
         causes quoted strings matching the specified null string to be
         converted to NULLs in <literal>CSV</> mode (Ian Barwick, Michael
         Paquier)
        </para>

        <para>
         Without this option, only unquoted matching strings will be imported
         as null values.
        </para>
       </listitem>

      <listitem>
       <para>
        Issue warnings for commands used outside of transaction blocks
        when they can have no effect (Bruce Momjian)
       </para>

       <para>
        New warnings are issued for <command>SET
        LOCAL</>, <command>SET CONSTRAINTS</>, <command>SET TRANSACTION</> and
        <command>ABORT</> when used outside a transaction block.
       </para>
      </listitem>

     </itemizedlist>

     <sect4>
      <title><xref linkend="SQL-EXPLAIN"></title>

      <itemizedlist>

       <listitem>
        <para>
         Make <command>EXPLAIN ANALYZE</> show planning time (Andreas
         Karlsson)
        </para>
       </listitem>

       <listitem>
        <para>
         Make <command>EXPLAIN</> show the grouping columns in Agg and
         Group nodes (Tom Lane)
        </para>
       </listitem>

       <listitem>
        <para>
         Make <command>EXPLAIN ANALYZE</> show exact and lossy
         block counts in bitmap heap scans (Etsuro Fujita)
        </para>
       </listitem>

      </itemizedlist>

     </sect4>

     <sect4>
      <title>Views</title>

      <itemizedlist>

      <listitem>
       <para>
        Allow <link linkend="rules-materializedviews">materialized views</>
        to be refreshed without blocking reads
        (Kevin Grittner)
       </para>

       <para>
        This is done with <link
        linkend="SQL-REFRESHMATERIALIZEDVIEW"><command>REFRESH MATERIALIZED
        VIEW CONCURRENTLY</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow views to be <link
        linkend="SQL-CREATEVIEW-updatable-views">automatically
        updated</link> even if they contain some non-updatable columns
        (Dean Rasheed)
       </para>

       <para>
        Previously the presence of non-updatable output columns such as
        expressions, literals, and function calls prevented automatic
        updates.  Now <command>INSERT</>s, <command>UPDATE</>s and
        <command>DELETE</>s are supported, provided that they do not
        attempt to assign new values to any of the non-updatable columns.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow control over whether <command>INSERT</>s and
        <command>UPDATE</>s can add rows to an auto-updatable view that
        would not appear in the view (Dean Rasheed)
       </para>

       <para>
        This is controlled with the new <xref linkend="SQL-CREATEVIEW">
        clause <literal>WITH CHECK OPTION</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link linkend="rules-privileges">security barrier views</>
        to be automatically updatable (Dean Rasheed)
       </para>
      </listitem>

      </itemizedlist>

     </sect4>

   </sect3>

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

     <itemizedlist>

      <listitem>
       <para>
        Support triggers on <link linkend="SQL-CREATEFOREIGNTABLE">foreign
        tables</> (Ronan Dunklau)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow moving groups of objects from one tablespace to another
        using the <literal>ALL IN TABLESPACE ... SET TABLESPACE</> form of
        <xref linkend="SQL-ALTERTABLE">, <xref linkend="SQL-ALTERINDEX">, or
        <xref linkend="SQL-ALTERMATERIALIZEDVIEW"> (Stephen Frost)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow changing foreign key constraint deferrability
        via <xref linkend="SQL-ALTERTABLE"> ... <literal>ALTER
        CONSTRAINT</> (Simon Riggs)
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce lock strength for some <xref linkend="SQL-ALTERTABLE">
        commands
        (Simon Riggs, Noah Misch, Robert Haas)
       </para>

       <para>
        Specifically, <literal>VALIDATE CONSTRAINT</>, <literal>CLUSTER
        ON</>, <literal>SET WITHOUT CLUSTER</>, <literal>ALTER COLUMN
        SET STATISTICS</>, <literal>ALTER COLUMN</> <literal>SET</>
        <option>(attribute_option)</>, <literal>ALTER COLUMN RESET</>
        <option>(attribute_option)</> no longer require <literal>ACCESS
        EXCLUSIVE</> locks.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow tablespace options to be set
        in <xref linkend="SQL-CREATETABLESPACE"> (Vik Fearing)
       </para>

       <para>
        Formerly these options could only be set
        via <xref linkend="SQL-ALTERTABLESPACE">.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <xref linkend="SQL-CREATEAGGREGATE"> to define the estimated
        size of the aggregate's transition state data (Hadi Moshayedi)
       </para>

       <para>
        Proper use of this feature allows the planner to better estimate
        how much memory will be used by aggregates.
       </para>
      </listitem>

      <listitem>
       <para>
        Fix <command>DROP IF EXISTS</> to avoid errors for non-existent
        objects in more cases (Pavel Stehule, Dean Rasheed)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve how system relations are identified (Andres Freund,
        Robert Haas)
       </para>

       <para>
        Previously, relations once moved into the <literal>pg_catalog</>
        schema could no longer be modified or dropped.
       </para>
      </listitem>

     </itemizedlist>

   </sect3>

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

    <itemizedlist>

      <listitem>
       <para>
        Fully implement the <link
        linkend="datatype-line"><type>line</></link> data type (Peter
        Eisentraut)
       </para>

       <para>
        The line <emphasis>segment</> data type (<link
        linkend="datatype-lseg"><type>lseg</></link>) has always been
        fully supported.  The previous <type>line</> data type (enabled
        only via a compile-time option) is not binary or dump-compatible.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link linkend="datatype-pg-lsn"><type>pg_lsn</></link>
        data type to represent a <acronym>WAL</> log sequence number
        (<acronym>LSN</>) (Robert Haas, Michael Paquier)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow single-point <link
        linkend="datatype-polygon"><type>polygon</></link>s to be converted
        to <link linkend="datatype-circle"><type>circle</></link>s
        (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
        Support time zone abbreviations that change from time to time
        (Tom Lane)
       </para>

       <para>
        Previously, <productname>PostgreSQL</> assumed that the UTC offset
        associated with a time zone abbreviation (such as <literal>EST</>)
        never changes in the usage of any particular locale.  However this
        assumption fails in the real world, so introduce the ability for a
        zone abbreviation to represent a UTC offset that sometimes changes.
        Update the zone abbreviation definition files to make use of this
        feature in timezone locales that have changed the UTC offset of their
        abbreviations since 1970 (according to the IANA timezone database).
       </para>
      </listitem>

      <listitem>
       <para>
        Allow 5+ digit years for non-<acronym>ISO</> <link
        linkend="datatype-datetime"><type>timestamp</></link> and
        <type>date</> strings, where appropriate (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
        Add checks for overflow/underflow of <link
        linkend="datatype-datetime"><type>interval</></link> values
        (Bruce Momjian)
       </para>
      </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="datatype-json"><acronym>JSON</></link></title>

     <itemizedlist>

       <listitem>
        <para>
         Add <link linkend="datatype-json"><type>jsonb</></link>, a more
         capable and efficient data type for storing <acronym>JSON</> data
         (Oleg Bartunov, Teodor Sigaev, Alexander
         Korotkov, Peter Geoghegan, Andrew Dunstan)
        </para>

        <para>
         This new type allows faster access to values in a JSON
         document and faster and more useful indexing of JSON columns.
         Scalar values in <type>jsonb</> documents are stored as appropriate
         scalar SQL types, and the JSON document structure is pre-parsed
         rather than being stored as text as in the original <type>json</>
         data type.
        </para>
       </listitem>

       <listitem>
        <para>
         Add new JSON functions to allow for the construction
         of arbitrarily complex JSON trees (Andrew Dunstan, Laurence Rowe)
        </para>

        <para>
         New functions include <link
         linkend="functions-json-processing-table"><function>json_array_elements_text()</></link>,
         <function>json_build_array()</>, <function>json_object()</>,
         <function>json_object_agg()</>, <function>json_to_record()</>,
         and <function>json_to_recordset()</>.
        </para>
       </listitem>

       <listitem>
        <para>
         Add <link
         linkend="functions-json-processing-table"><function>json_typeof()</></link>
         to return the data type of a <type>json</> value (Andrew Tipton)
        </para>
       </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Functions</title>

     <itemizedlist>

      <listitem>
       <para>
        Add <link
        linkend="functions-datetime-delay"><function>pg_sleep_for(interval)</></link>
        and <function>pg_sleep_until(timestamp)</> to specify
        delays more flexibly (Vik Fearing, Julien Rouhaud)
       </para>

       <para>
        The existing <function>pg_sleep()</> function only supports delays
        specified in seconds.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <link
        linkend="array-functions-table"><function>cardinality()</></link>
        function for arrays (Marko Tiikkaja)
       </para>

       <para>
        This returns the total number of elements in the array, or zero
        for an array with no elements.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <acronym>SQL</> functions to allow <link linkend="lo-funcs">large
        object reads/writes</link> at arbitrary offsets (Pavel Stehule)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <link
        linkend="array-functions-table"><function>unnest()</></link>
        to take multiple arguments, which are individually unnested then
        horizontally concatenated (Andrew Gierth)
       </para>
      </listitem>

      <listitem>
       <para>
        Add functions to construct <type>time</>s, <type>date</>s,
        <type>timestamp</>s, <type>timestamptz</>s, and <type>interval</>s
        from individual values, rather than strings (Pavel Stehule)
       </para>

       <para>
        These functions' names are prefixed with <literal>make_</>,
        e.g. <link linkend="functions-datetime-table"><function>make_date()</></link>.
       </para>
      </listitem>

      <listitem>
       <para>
        Make <link
        linkend="functions-formatting-table"><function>to_char()</></link>'s
        <literal>TZ</> format specifier return a useful value for simple
        numeric time zone offsets (Tom Lane)
       </para>

       <para>
        Previously, <literal>to_char(CURRENT_TIMESTAMP, 'TZ')</> returned
        an empty string if the <literal>timezone</> was set to a constant
        like <literal>-4</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add timezone offset format specifier <literal>OF</> to <link
        linkend="functions-formatting-table"><function>to_char()</></link>
        (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve the random seed used for <link
        linkend="functions-math-random-table"><function>random()</></link>
        (Honza Horak)
       </para>
      </listitem>

      <listitem>
       <para>
        Tighten validity checking for Unicode code points in <link
        linkend="functions-string-other"><function>chr(int)</></link>
        (Tom Lane)
       </para>

       <para>
        This function now only accepts values that are valid UTF8 characters
        according to RFC 3629.
       </para>
      </listitem>

     </itemizedlist>

    <sect4>
     <title>System Information Functions</title>

     <itemizedlist>

      <listitem>
       <para>
        Add functions for looking up objects in <structname>pg_class</>,
        <structname>pg_proc</>, <structname>pg_type</>, and
        <structname>pg_operator</> that do not generate errors for
        non-existent objects (Yugo Nagata, Nozomi Anzai,
        Robert Haas)
       </para>

       <para>
        For example, <link
        linkend="functions-info-catalog-table"><function>to_regclass()</></link>
        does a lookup in <structname>pg_class</> similarly to
        the <type>regclass</> input function, but it returns NULL for a
        non-existent object instead of failing.
       </para>
      </listitem>

      <listitem>
       <para>
        Add function <link
        linkend="functions-admin-dblocation"><function>pg_filenode_relation()</></link>
        to allow for more efficient lookup of relation names from filenodes
        (Andres Freund)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <structfield>parameter_default</> column to <link
        linkend="infoschema-parameters"><structname>information_schema.parameters</></link>
        view (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <link
        linkend="infoschema-schemata"><structname>information_schema.schemata</></link>
        show all accessible schemas (Peter Eisentraut)
       </para>

       <para>
        Previously it only showed schemas owned by the current user.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Aggregates</title>

     <itemizedlist>

      <listitem>
       <para>
        Add control over which rows are passed
        into aggregate functions using the <link
        linkend="syntax-aggregates"><literal>FILTER</></link> clause
        (David Fetter)
       </para>
      </listitem>

      <listitem>
       <para>
        Support ordered-set (<link
        linkend="syntax-aggregates"><literal>WITHIN GROUP</></link>)
        aggregates (Atri Sharma, Andrew Gierth, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Add aggregates <link
        linkend="functions-orderedset-table"><function>percentile_cont()</></link>,
        <function>percentile_disc()</>, <function>mode()</>, <link
        linkend="functions-hypothetical-table"><function>rank()</></link>,
        <function>dense_rank()</>, <function>percent_rank()</>, and
        <function>cume_dist()</>
        (Atri Sharma, Andrew Gierth)
       </para>
      </listitem>

      <listitem>
       <para>
        Support <link
        linkend="xfunc-sql-variadic-functions"><literal>VARIADIC</></link>
        aggregate functions (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow polymorphic aggregates to have non-polymorphic state data
        types (Tom Lane)
       </para>
       <para>
        This allows proper declaration of aggregates like the built-in
        aggregate <function>array_agg()</> in SQL.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

     <listitem>
      <para>
       Add event trigger support to <link linkend="plperl">PL/Perl</>
       and <link linkend="pltcl">PL/Tcl</> (Dimitri Fontaine)
      </para>
     </listitem>

     <listitem>
      <para>
       Convert <link linkend="datatype-numeric"><type>numeric</></link>
       values to <type>decimal</> in <link linkend="plpython">PL/Python</link>
       (Szymon Guz, Ronan Dunklau)
      </para>

      <para>
       Previously such values were converted to Python <type>float</> values,
       risking loss of precision.
      </para>
     </listitem>

    </itemizedlist>

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

     <itemizedlist>

      <listitem>
       <para>
        Add ability to store the PL/PgSQL
        call stack into a variable using <link
        linkend="plpgsql-get-diagnostics-context"><literal>PG_CONTEXT</></link>
        (Pavel Stehule, Stephen Frost)
       </para>
      </listitem>

      <listitem>
       <para>
        Add option <link
        linkend="plpgsql-statements-assignment"><option>print_strict_params</></link>
        to output parameters passed to queries generating <link
        linkend="plpgsql-statements-sql-onerow"><literal>STRICT</></link>
        errors (Marko Tiikkaja)
       </para>
      </listitem>

      <listitem>
       <para>
        Add variables <link
        linkend="plpgsql-extra-checks"><varname>plpgsql.extra_warnings</></link>
        and <varname>plpgsql.extra_errors</> to enable additional PL/pgSQL
        warnings and errors (Marko Tiikkaja, Petr Jelinek)
       </para>

       <para>
        Currently only shadowed variable errors/warnings are available.
       </para>
      </listitem>

    </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title><link linkend="libpq"><application>libpq</></link></title>
     <itemizedlist>

      <listitem>
       <para>
        Make libpq's <link
        linkend="libpq-pqconndefaults"><function>PQconndefaults()</></link>
        function ignore invalid service files (Steve Singer, Bruce Momjian)
       </para>

       <para>
        Previously it returned NULL if an incorrect service file was
        encountered.
       </para>
      </listitem>

      <listitem>
       <para>
        Accept <acronym>TLS</> protocol versions beyond <literal>TLSv1</>
        in libpq (Marko Kreen)
       </para>
      </listitem>

     </itemizedlist>

   </sect3>

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

    <itemizedlist>

      <listitem>
       <para>
        Add <xref linkend="APP-CREATEUSER"> option <option>-g</>
        to specify role membership (Chistopher Browne)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <xref linkend="APP-VACUUMDB">
        option <option>--analyze-in-stages</> to analyze in stages of
        increasing granularity (Peter Eisentraut)
       </para>

       <para>
        This allows minimal statistics to be created quickly.
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="APP-PGRESETXLOG"> with option <option>-n</>
        output current and potentially changed values (Rajeev Rastogi)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="app-initdb"> throw error for incorrect locale
        settings, rather than silently falling back to a default choice
        (Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="app-pg-ctl"> return exit code <literal>4</> for
        an inaccessible data directory (Amit Kapila, Bruce Momjian)
       </para>

       <para>
        This behavior more closely matches the Linux Standard Base
        (<acronym>LSB</>) Core Specification.
       </para>
      </listitem>

      <listitem>
       <para>
        On Windows, ensure that a non-absolute <option>-D</> path
        specification is interpreted relative
        to <xref linkend="app-pg-ctl">'s current directory
        (Kumar Rajeev Rastogi)
       </para>

       <para>
        Previously it would be interpreted relative to whichever directory
        the underlying Windows service was started in.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <function>sizeof()</> in <link linkend="ecpg">ECPG</link>
        C array definitions (Michael Meskes)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <link linkend="ecpg">ECPG</link> properly handle nesting
        of C-style comments in both C and <acronym>SQL</> text
        (Michael Meskes)
       </para>
      </listitem>

    </itemizedlist>

    <sect4>
     <title><xref linkend="APP-PSQL"></title>

     <itemizedlist>

      <listitem>
       <para>
        Suppress <quote>No rows</quote> output in <application>psql</> <link
        linkend="APP-PSQL-meta-commands"><option>expanded</></link>
        mode when the footer is disabled (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow Control-C to abort <application>psql</> when hung at connection
        startup (Peter Eisentraut)
       </para>
      </listitem>

     </itemizedlist>

     <sect5>
      <title><link linkend="APP-PSQL-meta-commands">Backslash Commands</link></title>

      <itemizedlist>

       <listitem>
        <para>
         Make <application>psql</> <command>\db+</> show tablespace options
         (Magnus Hagander)
        </para>
       </listitem>

       <listitem>
        <para>
         Make <application>psql</> <command>\do+</> display the functions
         which implement the operators (Marko Tiikkaja)
        </para>
       </listitem>

       <listitem>
        <para>
         Make <application>psql</> <command>\d+</> output an
         <literal>OID</> line only if an <literal>oid</literal> column
         exists in a table (Bruce Momjian)
        </para>

        <para>
         Previously, the presence or absence of an <literal>oid</literal>
         column was always reported.
        </para>
       </listitem>

       <listitem>
        <para>
         Make <command>\d</> show disabled system triggers (Bruce
         Momjian)
        </para>

        <para>
         Previously, if you disabled all triggers, only user triggers
         would show as disabled.
        </para>
       </listitem>

       <listitem>
        <para>
         Fix <application>psql</> <command>\copy</> to no longer require
         a space between <literal>stdin</> and a semicolon (Etsuro Fujita)
        </para>
       </listitem>

       <listitem>
        <para>
         Output the row count at the end
         of <application>psql</> <command>\copy</> just
         like <xref linkend="SQL-COPY"> (Kumar Rajeev Rastogi)
        </para>
       </listitem>

       <listitem>
        <para>
         Fix <application>psql</> <command>\conninfo</> to display the
         server's <acronym>IP</> address for clients that connect using
         <literal>hostaddr</> (Fujii Masao)
        </para>

        <para>
         Previously <command>\conninfo</> could not display the server's
         <acronym>IP</> address in such cases.
        </para>
       </listitem>

       <listitem>
        <para>
         Mention the <acronym>SSL</> protocol version in
         <application>psql</>'s <command>\conninfo</> (Marko Kreen)
        </para>
       </listitem>

       <listitem>
        <para>
         Add <application>psql</> tab completion for <command>\pset</>
         (Pavel Stehule)
        </para>
       </listitem>

       <listitem>
        <para>
         Allow <application>psql</>'s <command>\pset</> with no arguments
         to show all settings (Gilles Darold)
        </para>
       </listitem>

       <listitem>
        <para>
         In <application>psql</>, display the history file name written by
         <command>\s</> without converting it to an absolute path (Tom Lane)
        </para>

        <para>
         The code previously attempted to convert a relative file name to
         an absolute path for display, but frequently got it wrong.
        </para>
       </listitem>

      </itemizedlist>

     </sect5>

    </sect4>

    <sect4>
     <title><xref linkend="APP-PGDUMP"></title>

     <itemizedlist>

      <listitem>
       <para>
        Allow <xref linkend="APP-PGRESTORE"> options
        <option>-I</>, <option>-P</>, <option>-T</> and <option>-n</>
        to be specified multiple times (Heikki Linnakangas)
       </para>

       <para>
        This allows multiple objects to be restored in one operation.
       </para>
      </listitem>

      <listitem>
       <para>
        Optionally add <literal>IF EXISTS</> clauses to the <command>DROP</>
        commands emitted when removing old objects during a restore (Pavel
        Stehule)
       </para>

       <para>
        This change prevents unnecessary errors when removing old objects.
        The new <option>--if-exists</> option
        for <xref linkend="APP-PGDUMP">, <xref linkend="APP-PG-DUMPALL">,
        and <xref linkend="APP-PGRESTORE"> is only available
        when <option>--clean</> is also specified.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><xref linkend="app-pgbasebackup"></title>

     <itemizedlist>

      <listitem>
       <para>
        Add <application>pg_basebackup</> option <option>--xlogdir</>
        to specify the <filename>pg_xlog</> directory location (Haribabu
        Kommi)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <application>pg_basebackup</> to relocate tablespaces in
        the backup copy (Steeve Lennmark)
       </para>

       <para>
        This is particularly useful for using <application>pg_basebackup</>
        on the same machine as the primary.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow network-stream base backups to be throttled (Antonin Houska)
       </para>

       <para>
        This can be controlled with the <application>pg_basebackup</>
        <option>--max-rate</> parameter.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

     <itemizedlist>

      <listitem>
       <para>
        Improve the way tuples are frozen to preserve forensic information
        (Robert Haas, Andres Freund)
       </para>

       <para>
        This change removes the main objection to freezing tuples as soon
        as possible.  Code that inspects tuple flag bits will need to be
        modified.
       </para>
      </listitem>

      <listitem>
       <para>
        No longer require function prototypes for functions marked with the
        <link linkend="xfunc-c"><function>PG_FUNCTION_INFO_V1</></link>
        macro (Peter Eisentraut)
       </para>

       <para>
        This change eliminates the need to write boilerplate prototypes.
        Note that the <function>PG_FUNCTION_INFO_V1</> macro must appear
        before the corresponding function definition to avoid compiler
        warnings.
       </para>
      </listitem>

      <listitem>
       <para>
        Remove <varname>SnapshotNow</> and
        <function>HeapTupleSatisfiesNow()</> (Robert Haas)
       </para>

       <para>
        All existing uses have been switched to more appropriate snapshot
        types.  Catalog scans now use <acronym>MVCC</> snapshots.
       </para>
      </listitem>

      <listitem>
       <para>
        Add an <acronym>API</> to allow memory allocations over one gigabyte
        (Noah Misch)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <function>psprintf()</> to simplify memory allocation during
        string composition (Peter Eisentraut, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Support <function>printf()</> size modifier <literal>z</> to
        print <type>size_t</> values (Andres Freund)
       </para>
      </listitem>

      <listitem>
       <para>
        Change <acronym>API</> of <function>appendStringInfoVA()</>
        to better use <function>vsnprintf()</> (David Rowley, Tom Lane)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow new types of external toast datums to be created (Andres
        Freund)
       </para>
      </listitem>

      <listitem>
       <para>
        Add single-reader, single-writer, lightweight shared message queue
        (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve spinlock speed on x86_64 <acronym>CPU</>s (Heikki
        Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Remove spinlock support for unsupported platforms
        <productname>SINIX</>, <productname>Sun3</>, and
        <productname>NS32K</> (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Remove <acronym>IRIX</> port (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce the number of semaphores required by
        <option>--disable-spinlocks</> builds (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Rewrite <application>duplicate_oids</> Unix shell script in
        <application>Perl</> (Andrew Dunstan)
       </para>
      </listitem>

      <listitem>
       <para>
        Add Test Anything Protocol (<acronym>TAP</>) tests for client
        programs (Peter Eisentraut)
       </para>

       <para>
        Currently, these tests are run by <literal>make check-world</>
        only if the <option>--enable-tap-tests</> option was given
        to <application>configure</>.
        This might become the default in some future release.
       </para>
      </listitem>

      <listitem>
       <para>
        Add make targets <option>check-tests</> and
        <option>installcheck-tests</>, which allow selection of individual
        tests to be run (Andrew Dunstan)
       </para>
      </listitem>

      <listitem>
       <para>
        Remove <option>maintainer-check</> makefile rule (Peter Eisentraut)
       </para>

       <para>
        The default build rules now include all the formerly-optional tests.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve support for <envar>VPATH</> builds of <acronym>PGXS</>
        modules  (C&eacute;dric Villemain, Andrew Dunstan)
       </para>
      </listitem>

      <listitem>
       <para>
        Upgrade to Autoconf 2.69 (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
       <para>
        Add a <application>configure</> flag that appends custom text to the
        <envar>PG_VERSION</> string (Oskari Saarenmaa)
       </para>

       <para>
        This is useful for packagers building custom binaries.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve DocBook <acronym>XML</> validity (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
       <para>
        Various minor security and sanity fixes reported by the
        <productname>Coverity</> scanner (Stephen Frost)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve <application>Valgrind</> detection of invalid memory usage
        (Noah Misch)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve sample <application>Emacs</> configuration file
        <filename>emacs.samples</> (Peter Eisentraut)
       </para>

       <para>
        Also add <filename>.dir-locals.el</> to the top of the source tree.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <application>pgindent</> to accept a command-line list
        of typedefs (Bruce Momjian)
       </para>

       <para>
        <application>pgindent</> is also now smarter about blank lines
        around preprocessor conditionals.
       </para>
      </listitem>

      <listitem>
       <para>
        Avoid most uses of <command>dlltool</command>
        in <productname>Cygwin</> and
        <productname>Mingw</> builds (Marco Atzeri, Hiroshi Inoue)
       </para>
      </listitem>

      <listitem>
       <para>
        Support client-only installs in <acronym>MSVC</> (Windows) builds
        (MauMau)
       </para>
      </listitem>

     </itemizedlist>

   </sect3>

   <sect3>
    <title>Additional Modules</title>

    <itemizedlist>

      <listitem>
       <para>
        Add <xref linkend="pgprewarm"> extension to preload relation data
        into the shared buffer cache at server start (Robert Haas)
       </para>

       <para>
        This allows reaching full operating performance more quickly.
       </para>
      </listitem>

      <listitem>
       <para>
        Add <acronym>UUID</> random number generator
        <function>gen_random_uuid()</> to <xref linkend="pgcrypto">
        (Oskari Saarenmaa)
       </para>

       <para>
        This allows creation of version 4 <acronym>UUID</>s without
        requiring installation of <xref linkend="uuid-ossp">.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <xref linkend="uuid-ossp"> to work with
        the <systemitem>BSD</> or <systemitem>e2fsprogs</> UUID libraries,
        not only the <systemitem>OSSP</> UUID library (Matteo Beccati)
       </para>

       <para>
        This improves the <application>uuid-ossp</> module's portability
        since it no longer has to have the increasingly-obsolete OSSP
        library.  The module's name is now rather a misnomer, but we won't
        change it.
       </para>
      </listitem>

      <listitem>
       <para>
        Add option to <xref linkend="auto-explain"> to include trigger
        execution time (Horiguchi Kyotaro)
       </para>
      </listitem>

      <listitem>
       <para>
        Fix <xref linkend="pgstattuple"> to not report rows from
        uncommitted transactions as dead (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Make <xref linkend="pgstattuple"> functions
        use <type>regclass</type>-type arguments (Satoshi Nagayasu)
       </para>

       <para>
        While <type>text</type>-type arguments are still supported, they
        may be removed in a future major release.
       </para>
      </listitem>

      <listitem>
       <para>
        Improve consistency of <xref linkend="pgrowlocks"> output to honor
        snapshot rules more consistently (Robert Haas)
       </para>
      </listitem>

      <listitem>
       <para>
        Improve <xref linkend="pgtrgm">'s choice of trigrams for indexed
        regular expression searches by discouraging the selection of
        trigrams containing whitespace (Alexander Korotkov)
       </para>
      </listitem>

      <listitem>
       <para>
        Allow <xref linkend="pgxlogdump"> to report a live log stream
        with <option>--follow</> (Heikki Linnakangas)
       </para>
      </listitem>

      <listitem>
       <para>
        Store <xref linkend="cube"> data more compactly (Stas Kelvich)
       </para>

       <para>
        Existing data must be dumped/restored to use the new format.
        The old format can still be read.
       </para>
      </listitem>

      <listitem>
       <para>
        Reduce <xref linkend="vacuumlo"> client-side memory usage by using
        a cursor (Andrew Dunstan)
       </para>
      </listitem>

      <listitem>
       <para>
        Dramatically reduce memory consumption
        in <xref linkend="pgupgrade"> (Bruce Momjian)
       </para>
      </listitem>

      <listitem>
       <para>
        Pass <xref linkend="pgupgrade"> user name (<option>-U</> option) to
        analyze scripts (Bruce Momjian)
       </para>
      </listitem>

    </itemizedlist>

    <sect4>
     <title><xref linkend="pgbench"></title>

     <itemizedlist>

      <listitem>
       <para>
        Remove line length limit for <application>pgbench</> scripts (Sawada
        Masahiko)
       </para>

       <para>
        The previous line limit was <envar>BUFSIZ</>.
       </para>
      </listitem>

      <listitem>
       <para>
        Add long option names to <application>pgbench</> (Fabien Coelho)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <application>pgbench</> option <option>--rate</> to control
        the transaction rate (Fabien Coelho)
       </para>
      </listitem>

      <listitem>
       <para>
        Add <application>pgbench</> option <option>--progress</> to
        print periodic progress reports
        (Fabien Coelho)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><xref linkend="pgstatstatements"></title>

     <itemizedlist>

      <listitem>
       <para>
        Make <application>pg_stat_statements</> use a file, rather than
        shared memory, for query text storage (Peter Geoghegan)
       </para>

       <para>
        This removes the previous limitation on query text length, and
        allows a higher number of unique statements to be tracked by default.
       </para>
      </listitem>

      <listitem>
       <para>
        Allow reporting of <application>pg_stat_statements</>'s internal
        query hash identifier (Daniel Farina, Sameer Thakur, Peter
        Geoghegan)
       </para>
      </listitem>

      <listitem>
       <para>
        Add the ability to retrieve all <application>pg_stat_statements</>
        information except the query text (Peter Geoghegan)
       </para>

       <para>
        This allows monitoring tools to fetch query text only for
        just-created entries, improving performance during repeated querying
        of the statistics.
       </para>
      </listitem>

      <listitem>
       <para>
        Make <application>pg_stat_statements</> ignore <command>DEALLOCATE</>
        commands (Fabien Coelho)
       </para>

       <para>
        It already ignored <command>PREPARE</>, as well as planning time in
        general, so this seems more consistent.
       </para>
      </listitem>

      <listitem>
       <para>
        Save the statistics file into <filename>$PGDATA/pg_stat</> at server
        shutdown, rather than <filename>$PGDATA/global</> (Fujii Masao)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

  </sect2>
 </sect1>
