<!-- doc/src/sgml/release-12.sgml -->
<!-- See header comment in release.sgml about typical markup -->

 <sect1 id="release-12">
  <title>Release 12</title>

  <formalpara>
   <title>Release date:</title>
   <para>2019-??-?? AS OF 2019-05-09</para>
  </formalpara>

  <sect2>
   <title>Overview</title>

   <para>
    Major enhancements in <productname>PostgreSQL</productname> 12 include:
   </para>

   <!-- Items in this list summarize one or more items below -->

   <itemizedlist>

    <listitem>
     <para>big item</para>
    </listitem>

   </itemizedlist>

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

  </sect2>

  <sect2>

  <title>Migration to Version 12</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 12 contains a number of changes that may affect compatibility
    with previous releases.  Observe the following incompatibilities:
   </para>

   <itemizedlist>

    <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-11-20 [578b22971] Remove WITH OIDS support, change oid catalog column visi
-->

     <para>
      Remove the special behavior of <link
      linkend="datatype-oid">OID</link> columns (Andres Freund,
      John Naylor)
     </para>

     <para>
      Previously, a normally-invisible <type>OID</type> column could be
      specified during table creation using <literal>WITH OIDS</literal>;
      that ability has been removed.  Columns can still be explicitly
      specified as type <type>OID</type>.  Operations on tables that
      have columns named <type>OID</type> (created using <literal>WITH
      OIDS</literal>) will need adjustment.  <command>SELECT *</command>
      will now output those columns for the many system tables which
      have them.  Previously, the columns had to be selected explicitly.
     </para>
    </listitem>

    <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-10-11 [cda6a8d01] Remove deprecated abstime, reltime, tinterval datatypes.
-->

     <para>
      Remove data types <type>abstime</type>, <type>reltime</type>,
      and <type>tinterval</type> (Andres Freund)
     </para>
    </listitem>

    <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-10-11 [2d10defa7] Remove timetravel extension.
-->

     <para>
      Remove the <productname>timetravel</productname> extension
      (Andres Freund)
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-25 [2dedf4d9a] Integrate recovery.conf into postgresql.conf
-->

     <para>
      Move <filename>recovery.conf</filename> settings into <link
      linkend="runtime-config-wal-archive-recovery"><filename>postgresql.conf</filename></link>
      (Fujii Masao, Simon Riggs, Abhijit Menon-Sen, Sergei Kornilov)
     </para>

     <para>
      <filename>recovery.conf</filename> is no longer used,
      and the server will not start if the file exists.  <link
      linkend="runtime-config-wal-archive-recovery">recovery.signal</link>
      and standby.signal are now used to switch into non-primary
      mode.  <varname>trigger_file</varname> has been renamed
      to <xref linkend="guc-promote-trigger-file"/>.  The
      <varname>standby_mode</varname> setting has been removed.
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-28 [f2cbffc7a] Only allow one recovery target setting
-->

     <para>
      Do not allow multiple conflicting <link
      linkend="runtime-config-wal-recovery-target"><varname>recovery_target</varname>*</link>
      specifications (Peter Eisentraut)
     </para>

     <para>
      Specifically, only allow one of <xref
      linkend="guc-recovery-target"/>, <xref
      linkend="guc-recovery-target-lsn"/>,
      <xref linkend="guc-recovery-target-name"/>,
      <xref linkend="guc-recovery-target-time"/>, <xref
      linkend="guc-recovery-target-xid"/>.  Previously, multiple different
      instances of the variables above could be specified, and the last one
      was honored.  Now, only one can be specified, though the same one can
      be specified multiple times and the last specification is honored.
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-01-13 [0acb3bc33] Change default of recovery_target_timeline to <literal>latest</literal>
-->

     <para>
      Cause recovery to advance to the latest timeline by default
      (Peter Eisentraut)
     </para>

     <para>
      Specifically, <xref linkend="guc-recovery-target-time"/> now
      defaults to <literal>latest</literal>.  Previously, it defaulted
      to <literal>current</literal>.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2018-07-29 [a7dc63d90] Refactor geometric functions and operators
-->

     <para>
      Refactor <link linkend="functions-geometry">geometric
      functions</link> and operators (Emre Hasegeli)
     </para>

     <para>
      This could lead to more accurate, but slightly different, results
      from previous releases.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2018-08-16 [c4c340088] Use the built-in float datatypes to implement geometric 
-->

     <para>
      Restructure <link linkend="datatype-geometric">geometric
      types</link> to handle NaN, underflow, overflow and division by
      zero more consistently (Emre Hasegeli)
     </para>
    </listitem>

    <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2018-09-26 [2e2a392de] Fix problems in handling the line data type
-->

     <para>
      Improve behavior and error reporting for the <link
      linkend="datatype-geometric">line data type</link> (Emre Hasegeli)
     </para>
    </listitem>

    <listitem>
<!--
Author: Andrew Gierth <rhodiumtoad@postgresql.org>
2019-02-13 [02ddd4993] Change floating-point output format for improved perform
-->

     <para>
      Improve performance by changing the default number of trailing digits
      output for <link linkend="datatype-float"><type>REAL</type></link>
      and <type>DOUBLE PRECISION</type> values (Andrew Gierth)
     </para>

     <para>
      Previously, float values were output rounded to 6 or 15 decimals
      by default.  Now, only the number of digits required to preserve
      the exact binary value is output.  The previous  behavior can be
      restored by setting <xref linkend="guc-extra-float-digits"/> to zero.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-04-23 [c06e3550d] Don't request pretty-printed output from xmlNodeDump().
-->

     <para>
      Change <link linkend="functions-xml"><acronym>XML</acronym></link>
      functions like <function>xpath()</function> to never pretty-print
      their output (Tom Lane)
     </para>

     <para>
      Previously, this happened in some rare cases.  ACCURATE?  HOW TO
      GET PRETTY PRINT OUTPUT?
     </para>
    </listitem>

    <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-03-13 [6dd263cfa] Rename pg_verify_checksums to pg_checksums
-->

     <para>
      Rename command-line tool
      <application>pg_verify_checksums</application> to <xref
      linkend="app-pgchecksums"/> (Michaël Paquier)
     </para>
    </listitem>

    <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-04 [413ccaa74] pg_restore: Require -f - to mean stdout
-->

     <para>
      Require specification of <xref linkend="app-pgrestore"/>
      <literal>-f -</literal> to send the dump contents to stdout
      (Euler Taveira)
     </para>

     <para>
      The previous behavior was considered confusing.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-14 [eaf746a5b] Make psql's "\pset format" command reject non-unique abb
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-26 [a7eece4fc] Fix breakage of "\pset format latex".
-->

     <para>
      Disallow <application>psql</application>'s <command>\pset
      format</command> command from using non-unique abbreviations
      (Daniel Vérité)
     </para>

     <para>
      Previously, <command>\pset format a</command> chose
      <literal>aligned</literal>;  it will now error.
     </para>
    </listitem>

    <listitem>
<!--
This is caused by adding the tid to the btree entry, as listed later.
-->

     <para>
      The maximum btree index length is now reduced by eight bytes;
      a <xref linkend="sql-reindex"/> operation could potentially fail.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-19 [586b98fdf] Make type "name" collation-aware.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-04-05 [478cacb50] Ensure consistent name matching behavior in processSQLNa
-->

     <para>
      Allow data type <link
      linkend="datatype-character-special-table">name</link> to use
      non-C collations (Tom Lane, Daniel Vérité)
     </para>

     <para>
      It still uses the "C" collation by default, rather than defaulting
      to the database collation.  Regular expression operations on
      data type name columns will now use the "C" collation;  you will
      need to override the collation if you want to use locale-specific
      regular expression patterns, e.g., <command>\w</command>.
     </para>
    </listitem>

    <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-21 [bfb456c1b] Improve error reporting for DROP FUNCTION/PROCEDURE/AGGR
-->

     <para>
      Cause <link linkend="sql-dropfunction"><command>DROP IF EXISTS
      FUNCTION</command></link>/<literal>PROCEDURE</literal>/<literal>AGGREGATE</literal>/<literal>ROUTINE</literal>
      to generate an error if no arguments are supplied and there are
      multiple matching objects (David Rowley)
     </para>

     <para>
      Also improve the error message in such cases.
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-01 [96b00c433] Remove obsolete <structname>pg_constraint</structname>.consrc column
-->

     <para>
      Remove obsolete <link
      linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link>.<structfield>consrc</structfield>
      column (Peter Eisentraut)
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-01 [fe5038236] Remove obsolete pg_attrdef.adsrc column
-->

     <para>
      Remove obsolete <link
      linkend="catalog-pg-attrdef"><structname>pg_attrdef</structname></link>.<structfield>adsrc</structfield>
      column (Peter Eisentraut)
     </para>
    </listitem>

    <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-07-10 [bcbd94080] Remove dynamic_shared_memory_type=none
-->

     <para>
      Remove the ability to disable dynamic shared memory (Kyotaro
      Horiguchi)
     </para>

     <para>
      Specifically, <xref linkend="guc-dynamic-shared-memory-type"/>
      can no longer be set to <literal>none</literal>.
     </para>
    </listitem>

   </itemizedlist>

  </sect2>

  <sect2>
   <title>Changes</title>

    <para>
     Below you will find a detailed account of the changes between
     <productname>PostgreSQL</productname> 12 and the previous
     major release.
    </para>

   <sect3>
    <title>Server</title>

    <sect4>
     <title><link linkend="ddl-partitioning">Partitioning</link></title>

     <itemizedlist>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-07 [c6e4133fa] Postpone calculating total_table_pages until after pruni
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-15 [34c9e455d] Improve performance of partition pruning remapping a lit
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2018-11-16 [3f2393ede] Redesign initialization of partition routing structures
Author: Robert Haas <rhaas@postgresql.org>
2019-02-21 [9eefba181] Delay lock acquisition for partitions until we route a t
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-30 [428b260f8] Speed up planning when partitions can be pruned at plan 
-->

       <para>
        Improve performance of many operations on partitioned tables
        (Amit Langote, David Rowley, Tom Lane, Álvaro Herrera)
       </para>

       <para>
        Allow tables with thousands of child partitions to be processed
        efficiently by operations that only affect a small number of
        partitions.
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-03 [f56f8f8da] Support foreign keys that reference partitioned tables
-->

       <para>
        Allow <link linkend="ddl-constraints-fk">foreign keys</link>
        to reference partitioned tables (Álvaro Herrera)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-08-01 [0d5f05cde] Allow multi-inserts during COPY into a partitioned table
-->

       <para>
        Improve speed of <command>COPY</command> into partitioned tables
        (David Rowley)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-01-25 [7c079d741] Allow generalized expression syntax for partition bounds
-->

       <para>
        Allow partitions bounds to be any expression (Kyotaro Horiguchi,
        Tom Lane, Amit Langote)
       </para>

       <para>
        Expressions are evaluated at partitioned table creation time.
        Previously, only constants were allowed as partitions bounds.
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2018-12-17 [ca4103025] Fix tablespace handling for partitioned tables
-->

       <para>
        Allow <command>CREATE TABLE</command>'s tablespace specification
        for a partitioned table to affect the tablespace of its children
        (David Rowley, Álvaro Herrera)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-04-05 [959d00e9d] Use Append rather than MergeAppend for scanning ordered 
-->

       <para>
        Avoid sorting when partitions are already being scanned in the
        necessary order (David Rowley)
       </para>
      </listitem>

      <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-03-07 [898e5e329] Allow ATTACH PARTITION with only ShareUpdateExclusiveLoc
-->

       <para>
        <link linkend="sql-altertable"><command>ATTACH
        PARTITION</command></link> is now performed with reduced locking
        requirements (Robert Haas)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-02-08 [3677a0b26] Add pg_partition_root to display top-most parent of a pa
-->

       <para>
        Add function <link
        linkend="functions-info-partition"><function>pg_partition_root()</function></link>
        to return top-most parent of a partition tree (Michaël Paquier)
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-04 [b96f6b194] pg_partition_ancestors
-->

       <para>
        Add function <link
        linkend="functions-info-partition"><function>pg_partition_ancestors()</function></link>
        to report all ancestors of a partition (Álvaro Herrera)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-10-30 [d5eec4eef] Add pg_partition_tree to display information about parti
-->

       <para>
        Add function <link
        linkend="functions-info-partition"><function>pg_partition_tree()</function></link>
        to display information about partitions (Amit Langote)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-12-18 [f94cec644] Include partitioned indexes to system view pg_indexes
-->

       <para>
        Include partitioned indexes in the system view <link
        linkend="view-pg-indexes"><structname>pg_indexes</structname></link>
        (Suraj Kharage)
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-07 [1c5d9270e] psql \dP: list partitioned tables and indexes
-->

       <para>
        Add <application>psql</application> command <command>\dP</command>
        to list partitioned tables and indexes (Pavel Stěhule)
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2018-11-19 [d56e0fde8] psql: Describe partitioned tables/indexes as such
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-26 [1af25ca0c] Improve psql's \d display of foreign key constraints
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-17 [b036982db] psql: display tablespace for partitioned indexes
-->

       <para>
        Improve <application>psql</application> <command>\d</command>
        and <command>\z</command> display of partitioned tables (Pavel
        Stěhule, Michaël Paquier, Álvaro Herrera)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-02-11 [1d92a0c9f] Redesign the partition dependency mechanism.
-->

       <para>
        Fix bugs that could cause <command>ALTER TABLE DETACH
        PARTITION</command> to not drop objects that should be dropped,
        such as automatically-created child indexes (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Indexes</title>

     <itemizedlist>

      <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2018-07-28 [d2086b08b] Reduce path length for locking leaf B-tree pages during 
Author: Peter Geoghegan <pg@bowt.ie>
2019-03-25 [f21668f32] Add "split after new tuple" nbtree optimization.
-->

       <para>
        Improve speed of btree index insertions (Peter Geoghegan,
        Alexander Korotkov)
       </para>

       <para>
        The new code improves the space-efficiency of page splits,
        reduces locking overhead, and gives better performance for
        <command>UPDATE</command>s and <command>DELETE</command>s on
        indexes with many duplicates.
       </para>
      </listitem>

      <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2019-03-10 [f2e403803] Support for INCLUDE attributes in GiST indexes
-->

       <para>
        Support <link
        linkend="sql-createindex"><literal>INCLUDE</literal></link> columns
        in <link linkend="gist">GiST</link> indexes (Andrey Borodin)
       </para>
      </listitem>

      <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2018-09-19 [2a6368343] Add support for nearest-neighbor (KNN) searches to SP-Gi
-->

       <para>
        Add support for nearest-neighbor (<acronym>KNN</acronym>) searches
        of <link linkend="spgist">SP-GiST</link> indexes (Nikita Glukhov,
        Alexander Korotkov, Vlad Sterzhanov)
       </para>

      </listitem>

      <listitem>
<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2019-04-03 [9155580fd] Generate less WAL during GiST, GIN and SP-GiST index bui
-->

       <para>
        Reduce the <acronym>WAL</acronym> write overhead
        of <acronym>GiST</acronym>, <acronym>GIN</acronym> and
        <acronym>SP-GiST</acronym> index creation (Anastasia Lubennikova,
        Andrey V. Lepikhov)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-03 [80b9e9c46] Improve performance of index-only scans with many index 
-->

       <para>
        Allow index-only scans to be more efficient on indexes with many
        columns (Konstantin Knizhnik)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Geoghegan <pg@bowt.ie>
2019-03-20 [dd299df81] Make heap TID a tiebreaker nbtree index column.
Author: Peter Geoghegan <pg@bowt.ie>
2019-03-20 [fab250243] Consider secondary factors during nbtree splits.
-->

       <para>
        Have new btree indexes sort duplicate index entries in heap-storage
        order (Peter Geoghegan, Heikki Linnakangas)
       </para>

       <para>
        Indexes <application>pg_upgraded</application> from previous
        releases will not have this ordering.
       </para>
      </listitem>

      <listitem>
<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2019-03-05 [fe280694d] Scan GiST indexes in physical order during VACUUM.
-->

       <para>
        Improve the performance of vacuum scans of GiST indexes (Andrey
        Borodin, Konstantin Kuznetsov, Heikki Linnakangas)
       </para>
      </listitem>

      <listitem>
<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2019-03-22 [7df159a62] Delete empty pages during GiST VACUUM.
-->

       <para>
        Delete empty leaf pages during <acronym>GiST</acronym>
        <command>VACUUM</command> (Andrey Borodin)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-14 [1b5d797cd] Lower lock level for renaming indexes
-->

       <para>
        Reduce locking requirements for index renaming (Peter Eisentraut)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Optimizer</title>

     <itemizedlist>

      <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2019-03-27 [7300a6995] Add support for multivariate MCV lists
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2019-03-27 [a63b29a1d] Minor improvements for the multivariate MCV lists
-->

       <para>
        Allow <xref linkend="sql-createstatistics"/> to create
        most-common-value statistics for multiple columns (Tomas Vondra)
       </para>

       <para>
        This improves optimization for columns with non-uniform
        distributions that often appear in <literal>WHERE</literal>
        clauses.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-02-16 [608b167f9] Allow user control of CTE materialization, and change th
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-04-09 [947613127] Prevent inlining of multiply-referenced CTEs with outer 
-->

       <para>
        Allow <link linkend="queries-with">common table expressions</link>
        (<acronym>CTE</acronym>) to be inlined in later parts of the query
        (Andreas Karlsson, Andrew Gierth, David Fetter, Tom Lane)
       </para>

       <para>
        Specifically, <acronym>CTE</acronym>s are inlined
        if they are not recursive and are referenced only
        once later in the query.  Inlining can be prevented by
        specifying <literal>MATERIALIZED</literal>, and forced by
        specifying <literal>NOT MATERIALIZED</literal>.  Previously,
        <acronym>CTE</acronym>s were never inlined and were always
        evaluated before the rest of the query.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-07-16 [f7cb2842b] Add plan_cache_mode setting
-->

       <para>
        Allow control over when generic plans are used for prepared
        statements (Pavel Stěhule)
       </para>

       <para>
        This is controlled by the <xref linkend="guc-plan-cache_mode"/>
        server variable.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-30 [b5415e3c2] Support parameterized TidPaths.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-30 [0a6ea4001] Add a hash opclass for type "tid".
-->

       <para>
        Improve optimization of self-joins (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-13 [04fe805a1] Drop no-op CoerceToDomain nodes from expressions at plan
-->

       <para>
        Improve optimizations for <link
        linkend="sql-createdomain">domains</link> that have no check
        constraints (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-30 [6f19a8c41] Teach eval_const_expressions to constant-fold LEAST/GREA
-->

       <para>
        Inline calls to <link
        linkend="functions-greatest-least"><literal>LEAST</literal></link>
        and <literal>GREATEST</literal> to improve optimization (Vik
        Fearing)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-02-20 [e04a3905e] Improve planner's understanding of strictness of type co
-->

       <para>
        Allow <literal>IS NOT NULL</literal> with mis-matching types to
        use partial indexes more frequently (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-01 [65ce07e02] Teach optimizer's predtest.c more things about ScalarArr
-->

       <para>
        Allow IN comparisons with arrays to use <literal>IS NOT
        NULL</literal> partial indexes more frequently (James Coleman)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-14 [5e0928005] Make pg_statistic and related code account more honestly
-->

       <para>
        Store statistics using the collation defined for each column
        (Tom Lane)
       </para>

       <para>
        Previously, the default collation was used for all statistics
        storage.  This potentially gives better optimizer behavior for
        columns with non-default collations.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-25 [f7111f72d] Improve planner's selectivity estimates for inequalities
-->

       <para>
        Improve optimizer estimates for <link
        linkend="datatype-oid"><type>tid</type></link> inequality
        comparisons (Edmund Horner)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-07-11 [39a96512b] Mark built-in btree comparison functions as leakproof wh
-->

       <para>
        Fix the btree leakproof designation of some functions (Tom Lane)
       </para>

       <para>
        This allows for more complex optimizations.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

      <listitem>
<!--
Author: Bruce Momjian <bruce@momjian.us>
2018-09-21 [1f7fc7670] doc:  JIT is enabled by default in PG 12
-->

       <para>
        Enable <link linkend="jit">Just-in-Time</link>
        (<acronym>JIT</acronym>) compilation by default (Andres Freund)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2019-01-29 [36a1281f8] Separate per-batch and per-tuple memory contexts in COPY
Author: Andres Freund <andres@anarazel.de>
2019-01-26 [a9c35cf85] Change function call information to be variable length.
-->

       <para>
        Greatly reduce memory consumption of <xref linkend="sql-copy"/>
        and function calls (Andres Freund, Tomas Vondra, Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-01-06 [afb0d0712] Replace the data structure used for keyword lookup.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-01-09 [c64d0cd5c] Use perfect hashing, instead of binary search, for keywo
-->

       <para>
        Speed up keyword lookup (John Naylor, Joerg Sonnenberger, Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2019-01-25 [9556aa01c] Use single-byte Boyer-Moore-Horspool search even with mu
-->

       <para>
        Improve search performance for multi-byte characters (Heikki
        Linnakangas)
       </para>
      </listitem>

      <listitem>
<!--
Author: Stephen Frost <sfrost@snowman.net>
2019-04-02 [4d0e994ee] Add support for partial TOAST decompression
-->

       <para>
        Allow <link linkend="storage-toast"><literal>TOAST</literal></link>
        values to be minimally decompressed (Paul Ramsey)
       </para>

       <para>
        This is useful for routines that only look at values at the start
        of the <literal>TOAST</literal> field.
       </para>
      </listitem>

      <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-03-13 [bbb96c370] Allow ALTER TABLE .. SET NOT NULL to skip provably unnec
-->

       <para>
        Allow <link linkend="sql-altertable"><command>ALTER TABLE .. SET
        NOT NULL</command></link> to avoid unnecessary checking (Sergei
        Kornilov)
       </para>

       <para>
        This can happen if column constraints already prevent nulls.
       </para>
      </listitem>

      <listitem>
<!--
Author: Noah Misch <noah@leadboat.com>
2019-03-08 [3c5926301] Avoid some table rewrites for ALTER TABLE .. SET DATA TY
-->

       <para>
        Allow <command>ALTER TABLE .. SET DATA TYPE</command>
        <type>timestamp/timestamptz</type> to avoid a table rewrite when
        the session time zone is <acronym>UTC</acronym> (Noah Misch)
       </para>

       <para>
        In the <acronym>UTC</acronym> time zone, the data types are
        binary compatible.
       </para>
      </listitem>

      <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-07-22 [86eaf208e] Hand code string to integer conversion for performance.
-->

       <para>
        Improve speed in converting strings to
        <type>int2</type>/<type>int4</type> integers (Andres Freund)
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2019-03-15 [bb16aba50] Enable parallel query with SERIALIZABLE isolation.
-->

       <para>
        Allow parallelized queries when in <link
        linkend="sql-set-transaction"><literal>SERIALIZABLE</literal></link>
        isolation mode (Thomas Munro)
       </para>

       <para>
        Previously, parallelism was disabled when in this mode.
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2018-11-07 [3fd2a7932] Provide pg_pread() and pg_pwrite() for random I/O.
Author: Thomas Munro <tmunro@postgresql.org>
2018-11-07 [c24dcd0cf] Use pg_pread() and pg_pwrite() for data files and WAL.
-->

       <para>
        Use <function>pread()</function> and <function>pwrite()</function>
        for random I/O (Oskari Saarenmaa, Thomas Munro)
       </para>

       <para>
        This reduces the number of system calls required.

       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2018-07-24 [1bc180cd2] Use setproctitle_fast() to update the ps status, if avai
-->

       <para>
        Improve the speed of setting the <link
        linkend="guc-update-process-title">process title</link> on
        <systemitem class="osname">FreeBSD</systemitem> (Thomas Munro)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Monitoring</title>

     <itemizedlist>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2018-11-29 [88bdbd3f7] Add log_statement_sample_rate parameter
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-03 [799e22034] Log all statements from a sample of transactions
-->

       <para>
        Allow logging of only a percentage of statements and transactions
        meeting <xref linkend="guc-log-min-duration-statement"/> criteria
        (Adrien Nayrat)
       </para>

       <para>
        The parameters <xref linkend="guc-log-statement-sample-rate"/>
        and <xref linkend="guc-log-transaction-sample-rate"/> control this.
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-02 [ab0dfc961] Report progress of CREATE INDEX operations
Author: Peter Eisentraut <peter@eisentraut.org>
2019-04-07 [03f9e5cba] Report progress of REINDEX operations
-->

       <para>
        Report progress of <command>CREATE INDEX</command> and
        <command>REINDEX</command> operations (Álvaro Herrera, Peter
        Eisentraut)
       </para>

       <para>
        Progress is reported in the <link
        linkend="progress-reporting"><structname>pg_stat_progress_create_index</structname></link>
        system view
       </para>
      </listitem>

      <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-03-25 [6f97457e0] Add progress reporting for CLUSTER and VACUUM FULL.
-->

       <para>
        Add progress reporting to <command>CLUSTER</command> and
        <command>VACUUM FULL</command> (Tatsuro Yamada)
       </para>

       <para>
        Progress is reported in the <link
        linkend="vacuum-progress-reporting"><structname>pg_stat_progress_cluster</structname></link>
        system view.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-04-02 [280e5f140] Add progress reporting to pg_checksums
-->

       <para>
        Add progress reporting to <xref linkend="app-pgchecksums"/>
        (Michael Banck, Bernd Helmle)
       </para>

       <para>
        This is enabled with the option <option>--progress</option>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Magnus Hagander <magnus@hagander.net>
2019-03-09 [6b9e875f7] Track block level checksum failures in pg_stat_database
-->

       <para>
        Add counter of checksum failures to
        <structname>pg_stat_database</structname> (Magnus Hagander)
       </para>
      </listitem>

      <listitem>
<!--
Author: Magnus Hagander <magnus@hagander.net>
2019-04-12 [77bd49adb] Show shared object statistics in pg_stat_database
-->

       <para>
        Add tracking of global objects in system view
        <structname>pg_stat_database</structname> (Julien Rouhaud)
       </para>

       <para>
        Global objects have a <link
        linkend="pg-stat-database-view"><structname>pg_stat_database</structname></link>.<structfield>datoid</structfield>
        value of zero.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-10-09 [c48101620] Add pg_ls_archive_statusdir function
-->

       <para>
        Add the ability to list the contents of the archive directory
        (Christoph Moench-Tegeder)
       </para>

       <para>
        The function is <link
        linkend="functions-admin-genfile-table"><function>pg_ls_archive_statusdir()</function></link>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-10-05 [9cd92d1a3] Add pg_ls_tmpdir function
-->

       <para>
        Add the ability to list the contents of temporary directories
        (Nathan Bossart)
       </para>

       <para>
        The function, <link
        linkend="functions-admin-genfile-table"><function>pg_ls_tmpdir()</function></link>,
        optionally allows specification of a tablespace.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-02-01 [f60a0e967] Add more columns to pg_stat_ssl
-->

       <para>
        Add information about the client certificate to the system view
        <structname>pg_stat_ssl</structname> (Peter Eisentraut)
       </para>

       <para>
        The new columns are <structfield>client_serial</structfield>
        and <structfield>issuer_dn</structfield>.  Column
        <structfield>clientdn</structfield> has been renamed to
        <structfield>client_dn</structfield>, for clarity.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-02-21 [f9692a769] Hide other user's pg_stat_ssl rows
-->

       <para>
        Restrict visibility of rows in <link
        linkend="pg-stat-ssl-view"><structname>pg_stat_ssl</structname></link>
        by unprivileged users (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-01-30 [689d15e95] Log PostgreSQL version number on startup
-->

       <para>
        Add the version number to the server startup log message
        (Christoph Berg)
       </para>
      </listitem>

      <listitem>
<!--
Author: Andrew Dunstan <andrew@dunslane.net>
2019-03-06 [342cb650e] Don't log incomplete startup packet if it's empty
-->

       <para>
        Prevent logging of empty "incomplete" startup packets (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Stephen Frost <sfrost@snowman.net>
2018-09-28 [8bddc8640] Add application_name to connection authorized msg
-->

       <para>
        Unconditionally include <xref linkend="guc-application-name"/>
        in server log authentication messages (Don Seiler)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-02-27 [6ae578a91] Set fallback_application_name for a walreceiver to clust
-->

       <para>
        Have the walreceiver set its application name to the cluster name,
        if set (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-12-09 [7fee252f6] Add timestamp of last received message from standby to p
-->

       <para>
        Add the timestamp of the last received standby message to <link
        linkend="pg-stat-replication-view"><structname>pg_stat_replication</structname></link>
        (Lim MyungKyu)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-07-02 [c55de5e51] Add wait event for fsync of WAL segments
-->

       <para>
        Add <link linkend="wait-event-table">wait event</link> for fsync
        of <acronym>WAL</acronym> segments (Konstantin Knizhnik)
       </para>
      </listitem>

     </itemizedlist>

     <sect5>
      <title><link linkend="infoschema-tables">Information Schema</link></title>

      <itemizedlist>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-20 [7c15cef86] Base information_schema.sql_identifier domain on name, n
-->

       <para>
        Allow more use of indexes for text comparisons with
        <structname>information_schema</structname> columns (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-18 [6b0faf723] Make collation-aware system catalog columns use "C" coll
-->

       <para>
        Use "C" collation for <structname>information_schema</structname>
        and the system tables (Tom Lane)
       </para>

       <para>
        This will produce more consistent behavior in databases with
        different collations, but will also cause these tables to produce
        results in "C" collation ordering, rather than the default
        collation for the database.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-20 [5bbee34d9] Avoid producing over-length specific_name outputs in inf
-->

       <para>
        Force <structname>information_schema</structname> outputs to honor
        the system-defined maximum 63-byte identifier length (Tom Lane)
       </para>
      </listitem>

      </itemizedlist>

     </sect5>
    </sect4>

    <sect4>
     <title><acronym>Authentication</acronym></title>

     <itemizedlist>

      <listitem>
<!--
Author: Stephen Frost <sfrost@snowman.net>
2019-04-03 [b0b39f72b] GSSAPI encryption support
-->

       <para>
        Add <link linkend="gssapi-auth"><acronym>GSSAPI</acronym></link>
        client and server-side encryption support (Robbie Harwood,
        Stephen Frost)
       </para>

       <para>
        Add <link
        linkend="auth-pg-hba-conf"><filename>pg_hba.conf</filename></link>
        <link
        linkend="auth-pg-hba-conf"><literal>hostgssenc</literal></link>
        and <literal>hostnogssenc</literal> record types.  This would
        typically use the <literal>gss</literal> authentication method.
        This also adds a libpq <xref linkend="libpq-connect-gssencmode"/>
        option, and a <xref linkend="pg-stat-gssapi-view"/> system view.
       </para>
      </listitem>

      <listitem>
<!--
Author: Magnus Hagander <magnus@hagander.net>
2019-03-09 [0516c61b7] Add new clientcert hba option verify-full
-->

       <para>
        Allow the <link
        linkend="auth-cert"><literal>clientcert</literal></link>
        <filename>pg_hba.conf</filename> option to check that the database
        user name matches the certificate common name (Julian Markwort,
        Marius Timmer)
       </para>

       <para>
        The new check is enabled with
        <literal>clientcert=verify-full</literal>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2019-03-21 [0f086f84a] Add DNS SRV support for LDAP server discovery.
-->

       <para>
        Allow discovery of the <link
        linkend="auth-ldap"><acronym>LDAP</acronym></link> server using
        <acronym>DNS SRV</acronym> records (Thomas Munro)
       </para>

       <para>
        This avoids the requirement of specifying
        <literal>ldapserver</literal>, and is only supported if
        <productname>PostgreSQL</productname> is compiled with
        <productname>OpenLDAP</productname>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-08-10 [f841ceb26] Improve TRUNCATE by avoiding early lock queue
-->

       <para>
        Prevent <xref linkend="sql-truncate"/> from requesting a lock on
        tables for which the user lacks permission (Michaël Paquier)
       </para>

       <para>
        This prevents unauthorized locking delays.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-08-27 [a556549d7] Improve VACUUM and ANALYZE by avoiding early lock queue
-->

       <para>
        Prevent <command>VACUUM</command> and <command>ANALYZE</command>
        from requesting a lock on tables for which it lacks permission
        (Michaël Paquier)
       </para>

       <para>
        This prevents unauthorized locking delays.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Server Configuration</title>

     <itemizedlist>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-03-23 [ed308d783] Add options to enable and disable checksums in pg_checks
-->

       <para>
        Add ability to enable/disable cluster checksums using <xref
        linkend="app-pgchecksums"/> (Michael Banck, Michaël Paquier)
       </para>

       <para>
        The cluster must be offline for these operations.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-10 [cbccac371] Reduce the default value of autovacuum_vacuum_cost_delay
-->

       <para>
        Reduce the default value of <xref
        linkend="guc-autovacuum-vacuum-cost-delay"/> to 2ms (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi
-->

       <para>
        Allow <xref linkend="guc-vacuum-cost-delay"/> to specify
        sub-millisecond delays (Tom Lane)
       </para>

       <para>
        Floating-point values can also now be specified.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi
-->

       <para>
        Allow time-based server variables to use <link
        linkend="config-setting">micro-seconds</link> (us) (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-11 [1a83a80a2] Allow fractional input values for integer GUCs, and impr
-->

       <para>
        Allow fractional input for integer server variables (Tom Lane)
       </para>

       <para>
        For example, <command>SET work_mem = '30.1GB'</command>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-10 [caf626b2c] Convert [autovacuum_]vacuum_cost_delay into floating-poi
-->

       <para>
        Allow units to be specified for floating-point server variables
        (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2019-04-02 [475861b26] Add wal_recycle and wal_init_zero GUCs.
-->

       <para>
        Add <xref linkend="guc-wal-recycle"/> and <xref
        linkend="guc-wal-init-zero"/> server variables to avoid
        <acronym>WAL</acronym> file recycling (Jerry Jelinek)
       </para>

       <para>
        This can be beneficial on copy-on-write file systems like
        <productname>ZFS</productname>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-04-06 [249d64999] Add support TCP user timeout in libpq and the backend se
-->

       <para>
        Add parameter to control the server <acronym>TCP</acronym> timeout
        (Ryohei Nagaura)
       </para>

       <para>
        The parameter is <xref linkend="guc-tcp-user-timeout"/>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-20 [e73e67c71] Add settings to control SSL/TLS protocol version
-->

       <para>
        Allow control of the minimum and maximum <acronym>SSL</acronym>>
        protocol versions (Peter Eisentraut)
       </para>

       <para>
        The server settings are <xref
        linkend="guc-ssl-min-protocol-version"/> and <xref
        linkend="guc-ssl-max-protocol-version"/>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-07-30 [98efa76fe] Add ssl_library preset parameter
-->

       <para>
        Add server variable <xref linkend="guc-ssl-library"/> to report
        the <acronym>SSL</acronym> library version used by the server
        (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2019-02-03 [f1bebef60] Add shared_memory_type GUC.
-->

       <para>
        Add server variable to control the type of shared memory to use
        (Andres Freund)
       </para>

       <para>
        The variable is <xref linkend="guc-shared-memory-type"/>.
        Its purpose is to allow selection of <productname>System
        V</productname> shared memory, if desired.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-02-07 [13b89f96d] Allow some recovery parameters to be changed with reload
-->

      <para>
       Allow some recovery parameters to be changed with reload (Peter
       Eisentraut)
      </para>

      <para>
       These parameters are <xref linkend="guc-archive-cleanup-command"/>,
       <xref linkend="guc-promote-trigger-file"/>, <xref
       linkend="guc-recovery-end-command"/>, and <xref
       linkend="guc-recovery-min-apply-delay"/>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-09-22 [db361db2f] Make GUC wal_sender_timeout user-settable
-->

      <para>
       Allow the streaming replication timeout (<xref
       linkend="guc-wal-sender-timeout"/>) to be set per connection
       (Tsunakawa Takayuki)
      </para>

      <para>
       Previously, this could only be set cluster-wide.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-10-25 [10074651e] Add pg_promote function
Author: Michael Paquier <michael@paquier.xyz>
2018-11-06 [8f045e242] Switch pg_promote to be parallel-safe
-->

      <para>
       Add function <link
       linkend="functions-recovery-control"><function>pg_promote()</function></link>
       to promote standbys to primaries (Laurenz Albe, Michaël Paquier)
      </para>

      <para>
       Previously, this operation was only possible by using <xref
       linkend="app-pg-ctl"/> or creating a trigger file.
      </para>
     </listitem>

     <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-04-05 [9f06d79ef] Add facility to copy replication slots
-->

      <para>
       Allow replication slots to be copied (Masahiko Sawada)
      </para>

      <para>
       The functions are <link
       linkend="functions-replication-table"><function>pg_copy_physical_replication_slot()</function></link>
       and <function>pg_copy_logical_replication_slot()</function>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-02-12 [ea92368cd] Move max_wal_senders out of max_connections for connecti
-->

      <para>
       Have <xref linkend="guc-max-wal-senders"/> not count as part of
       <xref linkend="guc-max-connections"/> (Alexander Kukushkin)
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-01-11 [ff8530605] Add value 'current' for recovery_target_timeline
-->

      <para>
       Add an explicit value of <literal>current</literal> for <xref
       linkend="guc-recovery-target-time"/> (Peter Eisentraut)
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-09-07 [8582b4d04] Improve handling of corrupted two-phase state files at r
-->

      <para>
       Have recovery fail if a <link
       linkend="sql-prepare-transaction">two-phase transaction</link>
       status file is corrupt (Michaël Paquier)
      </para>

      <para>
       Previously, only a warning was issued in the logs and recovery
       continued.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-29 [5dc92b844] REINDEX CONCURRENTLY
-->

      <para>
       Add <xref linkend="sql-reindex"/> <literal>CONCURRENTLY</literal>
       to allow reindexing concurrently (Michaël Paquier, Andreas
       Karlsson, Peter Eisentraut)
      </para>

      <para>
       This is also controlled by the <xref linkend="app-reindexdb"/>
       <option>--concurrently</option> option.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-30 [fc22b6623] Generated columns
-->

      <para>
       Add support for <link linkend="sql-createtable">generated
       columns</link> (Peter Eisentraut)
      </para>

      <para>
       The content of generated columns are computed from expressions
       (including references to other columns in the same table)
       rather than being specified by <command>INSERT</command> or
       <command>UPDATE</command> commands.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2019-01-20 [31f381740] Allow COPY FROM to filter data using WHERE conditions
-->

      <para>
       Add a <literal>WHERE</literal> clause to <command>COPY
       FROM</command> which controls which rows are output (Surafel
       Temesgen)
      </para>
     </listitem>

     <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2018-10-09 [212fab992] Relax transactional restrictions on ALTER TYPE ... ADD V
-->

      <para>
       Allow enumerated values to be added in more transaction types
       (Andrew Dunstan, Tom Lane, Thomas Munro)
      </para>

      <para>
       Previously, <link linkend="sql-altertype"><command>ALTER
       TYPE ... ADD VALUE</command></link> could only be called in
       a transaction that created the enumerated type.  Now, the only
       restriction is that the new enumerated value cannot be referenced
       until the transaction commits.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-24 [280a408b4] Transaction chaining
-->

      <para>
       Add command to end a transaction and start a new one (Peter
       Eisentraut)
      </para>

      <para>
       The commands are <link linkend="sql-commit"><command>COMMIT AND
       CHAIN</command></link> and <command>ROLLBACK AND CHAIN</command>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-22 [5e1963fb7] Collations with nondeterministic comparison
-->

      <para>
       Allow the creation of <link
       linkend="sql-createcollation">collations</link> that report
       string equality for strings that are not byte-wise equal (Peter
       Eisentraut)
      </para>

      <para>
       This allows case and accent-agnostic equality comparisons using
       "nondeterministic" collations.  This is only supported for
       <acronym>ICU</acronym> collations.  MENTION ITS AFFECT ON ORDERING?
      </para>
     </listitem>

     <listitem>
<!--
Author: Fujii Masao <fujii@postgresql.org>
2019-04-08 [119dcfad9] Add vacuum_truncate reloption.
Author: Fujii Masao <fujii@postgresql.org>
2019-05-08 [b84dbc8eb] Add TRUNCATE parameter to VACUUM.
-->

      <para>
       Add <xref linkend="sql-vacuum"/> and <command>CREATE
       TABLE</command> options to prevent <command>VACUUM</command>
       from truncating trailing empty pages (Tsunakawa Takayuki)
      </para>

      <para>
       The options are <varname>vacuum_truncate</varname> and
       <varname>toast.vacuum_truncate</varname>.  This reduces vacuum
       locking requirements.
      </para>
     </listitem>

     <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-04-04 [a96c41fee] Allow VACUUM to be run with index cleanup disabled.
-->

      <para>
       Allow vacuum to avoid index cleanup with the
       <literal>INDEX_CLEANUP</literal> option (Masahiko Sawada)
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-10-04 [803b1301e] Add option SKIP_LOCKED to VACUUM and ANALYZE
-->

      <para>
       Add the ability to skip <command>VACUUM</command> and
       <command>ANALYZE</command> operations on tables that cannot be
       immediately locked (Nathan Bossart)
      </para>

      <para>
       This option is called <literal>SKIP_LOCKED</literal>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-03-29 [41b54ba78] Allow existing VACUUM options to take a Boolean argument
-->

      <para>
       Allow <command>VACUUM</command> and <command>ANALYZE</command>
       to take optional boolean argument specifications (Masahiko Sawada)
      </para>
     </listitem>

     <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2019-04-04 [ea569d64a] Add SETTINGS option to EXPLAIN, to print modified settin
-->

      <para>
       Add <xref linkend="sql-explain"/> option
       <literal>SETTINGS</literal> to output non-default optimizer
       settings (Tomas Vondra)
      </para>

      <para>
       This can also be output in auto-explain via <xref
       linkend="auto-explain"/>.<literal>log_settings</literal>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Andrew Gierth <rhodiumtoad@postgresql.org>
2019-03-19 [01bde4fa4] Implement OR REPLACE option for CREATE AGGREGATE.
-->

      <para>
       Allow aggregates to be replaced (Andrew Gierth)
      </para>

      <para>
       The command is <link linkend="sql-createaggregate"><command>CREATE
       OR REPLACE AGGREGATE</command></link>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-19 [590a87025] Ignore attempts to add TOAST table to shared or catalog 
-->

      <para>
       Allow modifications of system table options using <xref
       linkend="sql-altertable"/> (Peter Eisentraut)
      </para>

      <para>
       This allows modifications of <literal>reloptions</literal> and
       autovacuum settings.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-01-30 [5f5c01459] Allow RECORD and RECORD[] to be specified in function co
-->

      <para>
       Allow <type>RECORD</type> and <type>RECORD[]</type> to be used
       as column types in a query's column definition list for a <link
       linkend="sql-createfunction">table function</link> that is declared
       to return <type>RECORD</type> (Elvis Pranskevichus)
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-13 [f177660ab] Include all columns in default names for foreign key con
-->

      <para>
       Use all column names when creating default foreign key constraint
       names (Peter Eisentraut)
      </para>

      <para>
       Previously, only the first column name was used.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-24 [fd582317e] Sync our Snowball stemmer dictionaries with current upst
-->

      <para>
       Update Snowball stemmer dictionaries with support for new languages
       (Arthur Zakirov)
      </para>

      <para>
       This adds additional stemming languages to <link
       linkend="textsearch">full text search</link>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-17 [b8f9a2a69] Add support for collation attributes on older ICU versio
-->

      <para>
       Add support for <acronym>ICU</acronym> collation customization
       attributes (Peter Eisentraut)
      </para>

      <para>
       This allow modification of the collation rules.  DETAILS?
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-19 [2ece7c07d] Add text-vs-name cross-type operators, and unify name_op
-->

      <para>
       Allow data type <link linkend="datatype-oid">name</link> to more
       seamlessly be compared to other text types (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Functions</title>

    <itemizedlist>

     <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2019-03-16 [72b646033] Partial implementation of SQL/JSON path language
Author: Alexander Korotkov <akorotkov@postgresql.org>
2019-03-16 [16d489b0f] Numeric error suppression in jsonpath
Author: Alexander Korotkov <akorotkov@postgresql.org>
2019-04-01 [0a02e2ae0] GIN support for @@ and @? jsonpath operators
-->

      <para>
       Add support for the <acronym>SQL/JSON</acronym> <link
       linkend="functions-json-processing-table">path</link> language
       (Nikita Glukhov, Teodor Sigaev, Alexander Korotkov, Oleg Bartunov,
       Liudmila Mantrova)
      </para>

      <para>
       This allows execution of complex queries on <type>JSON</type>
       values using an <acronym>SQL</acronym>-standard language.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-03-12 [f1d85aa98] Add support for hyperbolic functions, as well as log10()
-->

      <para>
       Add support for <link linkend="functions-math-hyp-table">hyperbolic
       functions</link> (Lætitia Avrot)
      </para>

      <para>
       Also add <function>log10()</function> as alias for
       <function>log()</function>, for standards compliance.
      </para>
     </listitem>

     <listitem>
<!--
Author: Dean Rasheed <dean.a.rasheed@gmail.com>
2018-10-06 [e954a727f] Improve the accuracy of floating point statistical aggre
-->
      <para>
       Improve the accuracy of statistical aggregates like <link
       linkend="functions-aggregate-statistics-table"><function>variance()</function></link>
       by using more precise algorithms (Dean Rasheed)
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-14 [600b04d6b] Add a timezone-specific variant of date_trunc().
-->

      <para>
       Allow <link
       linkend="functions-datetime-table"><function>date_trunc()</function></link>
       to have an additional argument to control the time zone (Vik
       Fearing, Tom Lane)
      </para>

      <para>
       This is faster and simpler than using the <literal>AT TIME
       ZONE</literal> clause.
      </para>
     </listitem>

     <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2018-09-09 [cf9846724] Improve behavior of to_timestamp()/to_date() functions
-->

      <para>
       Adjust <link
       linkend="functions-formatting-table"><function>to_timestamp()</function></link>/<function>to_date()</function>
       functions to be more forgiving of template mismatches (Artur
       Zakirov, Alexander Korotkov, Liudmila Mantrova)
      </para>

      <para>
       This new behavior more closely matches the
       <productname>Oracle</productname> functions of the same name.
       DETAILS?
      </para>
     </listitem>

     <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-07 [251cf2e27] Fix minor deficiencies in XMLTABLE, xpath(), xmlexists()
-->

      <para>
       Improve node detection and escaping of <link
       linkend="functions-xml"><acronym>XML</acronym> functions</link>
       (Pavel Stěhule, Markus Winand, Chapman Flack)
      </para>

      <para>
       Specifically, in <literal>XMLTABLE</literal>,
       <function>xpath()</function>, and <function>xmlexists()</function>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-07 [eaaa5986a] Fix the BY {REF,VALUE} clause of XMLEXISTS/XMLTABLE
-->

      <para>
       Allow the <literal>XML BY VALUE</literal> clause (Chapman Flack)
      </para>

      <para>
       The clause has no effect.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-03-27 [5bde1651b] Switch function current_schema[s]() to be parallel-unsaf
-->

      <para>
       Prevent <link
       linkend="functions-info-session-table"><function>current_schema()</function></link>
       and <function>current_schemas()</function> from being run by
       parallel workers (Michaël Paquier)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title><link linkend="plpgsql">PL/pgSQL</link></title>

    <itemizedlist>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-01-04 [4879a5172] Support plpgsql variable names that conflict with unrese
-->

      <para>
       Allow commands and variables with the same name as commands to
       be used in the same PL/pgSQL function (Tom Lane)
      </para>

      <para>
       For example, allow a variable called comment to exist in the same
       function that calls the comment <acronym>SQL</acronym> command.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2018-07-25 [167075be3] Add strict_multi_assignment and too_many_rows plpgsql ch
-->

      <para>
       Add new optional warning and error checks to PL/pgSQL (Pavel
       Stěhule)
      </para>

      <para>
       The new checks allow for run-time validation of
       <literal>INTO</literal> column counts and single-row results.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Client Interfaces</title>

    <itemizedlist>

     <listitem>
<!--
Author: Michael Meskes <meskes@postgresql.org>
2019-02-18 [050710b36] Add bytea datatype to ECPG.
-->

      <para>
       Allow <xref linkend="app-ecpg"/> to create variables of data type
       bytea (Ryo Matsumura)
      </para>

      <para>
       This allows to interaction with <type>bytea</type> data directly,
       rather than using a binary encoding.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Meskes <meskes@postgresql.org>
2019-02-16 [bd7c95f0c] Add DECLARE STATEMENT support to ECPG.
-->

      <para>
       Add <command>DECLARE STATEMENT</command> support to
       <productname>ECPG</productname> (Takeshi Ideriha, Hayato Kuroda)
      </para>

      <para>
       This allows statements to be associated with named connections,
       so future operations like cursors don't need to re-reference the
       connection name.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-04-06 [249d64999] Add support TCP user timeout in libpq and the backend se
-->

      <para>
       Add parameter to control libpq's <acronym>TCP</acronym> timeout
       (Ryohei Nagaura)
      </para>

      <para>
       The parameter is <xref linkend="libpq-tcp-user-timeout"/>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-04-04 [7bac3acab] Add a "SQLSTATE-only" error verbosity option to libpq an
-->

      <para>
       Allow libpq to report the <literal>SQLSTATE</literal> to output
       only this value (Didier Gautheron)
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-11 [2970afa6c] Add PQresultMemorySize function to report allocated size
-->

      <para>
       Add libpq function to report the memory size of the query result
       (Lars Kanis, Tom Lane)
      </para>

      <para>
       The function is <link
       linkend="libpq-pqresultmemorysize"><function>PQresultMemorySize()</function></link>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-09-07 [1fea1e325] libpq: Change "options" dispchar to normal
-->

      <para>
       Remove the no-display/debug flag from the libpq
       <literal>options</literal> parameter (Peter Eisentraut)
      </para>

      <para>
       This allows the option to be used by
       <application>postgres_fdw</application>.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-04-01 [cc8d41511] Unified logging system for command-line programs
-->

      <para>
       Add colorization to the output of command-line utilities (Peter
       Eisentraut)
      </para>

      <para>
       This is enabled with by setting environment variable
       <envar>PG_COLORS</envar>.  EXAMPLE?
      </para>
     </listitem>

     </itemizedlist>

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

     <itemizedlist>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-26 [aa2ba50c2] Add CSV table output mode in psql.
-->

       <para>
        Add <acronym>CSV</acronym> table output mode in
        <application>psql</application> (Daniel Vérité)
       </para>

       <para>
        This is controlled by <command>\pset format csv</command> or the
        command-line <option>--csv</option> option.
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-11 [27f3dea64] psql: Add documentation URL to \help output
-->

       <para>
        Show the manual page <acronym>URL</acronym> in
        <application>psql</application>'s <command>\help</command> output
        (Peter Eisentraut)
       </para>
      </listitem>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2018-11-19 [6e5f8d489] psql: Show IP address in \conninfo
-->

       <para>
        Display the <acronym>IP</acronym> address in
        <application>psql</application>'s <command>\conninfo</command>
        (Fabien Coelho)
       </para>
      </listitem>

      <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-12-23 [11a60d496] Add completion for storage parameters after CREATE TABLE
Author: Michael Paquier <michael@paquier.xyz>
2018-10-26 [5953c9969] Improve tab completion of CREATE EVENT TRIGGER in psql
Author: Michael Paquier <michael@paquier.xyz>
2018-10-26 [292ef6e27] Add tab completion of EXECUTE FUNCTION for CREATE TRIGGE
Author: Michael Paquier <michael@paquier.xyz>
2019-01-28 [23349b18d] Add tab completion for ALTER INDEX ALTER COLUMN in psql
Author: Michael Paquier <michael@paquier.xyz>
2018-12-20 [4cba9c2a3] Add more tab completion for CREATE TABLE in psql
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-20 [a7c4dad1a] Fix psql's tab completion for ALTER DATABASE ... SET TAB
Author: Michael Paquier <michael@paquier.xyz>
2018-12-25 [f89ae34ab] Improve tab completion of ALTER INDEX/TABLE with SET STA
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-20 [c9a8a401f] Fix psql's tab completion for TABLE.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-21 [121213d9d] Improve tab completion for ANALYZE, EXPLAIN, and VACUUM.
-->

       <para>
        Improve tab completion of <command>CREATE TABLE, CREATE TRIGGER,
        CREATE EVENT TRIGGER, ANALYZE, EXPLAIN, VACUUM, ALTER TABLE,
        ALTER INDEX, ALTER DATABASE, ALTER INDEX ALTER COLUMN</command>
        (Dagfinn Ilmari Mannsåker, Tatsuro Yamada, Michaël Paquier,
        Tom Lane, Justin Pryzby)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-01-10 [6260cc550] pgbench: add \cset and \gset commands
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-25 [25ee70511] pgbench: Remove \cset
-->

       <para>
        Allow values produced by queries to be assigned to pgbench
        variables (Fabien Coelho, Álvaro Herrera)
       </para>

       <para>
        The commands is <command>\gset</command>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-25 [5b7e03670] Avoid unnecessary precision loss for pgbench's - -rate ta
-->

       <para>
        Improve precision of pgbench's <option>--rate</option>
        option (Tom Lane)
       </para>
      </listitem>

      <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-10-15 [5b75a4f82] pgbench: Report errors during run better
-->
       <para>
        Improve pgbench error reporting with clearer messages and return
        codes (Peter Eisentraut)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Server Applications</title>

    <itemizedlist>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-01-31 [00d1e88d3] Add - -min-xid-age and - -min-mxid-age options to vacuumdb
-->

      <para>
       Allow <xref linkend="app-vacuumdb"/> to select tables for vacuum
       based on their wraparound horizon (Nathan Bossart)
      </para>

      <para>
       The options are <option>--min-xid-age</option> and
       <option>--min-mxid-age</option>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-01-08 [354e95d1f] Add - -disable-page-skipping and - -skip-locked to vacuumd
-->

      <para>
       Add vacuumdb to disable waiting for locks or skipping all-visible
       pages (Nathan Bossart)
      </para>

      <para>
       The options are <option>--skip-locked</option> and
       <option>--disable-page-skipping</option>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2018-09-01 [ec7436993] Implement "pg_ctl logrotate" command
-->

      <para>
       Allow control of log file rotation via <xref linkend="app-pg-ctl"/>
       (Kyotaro Horiguchi, Alexander Kuzmenkov, Alexander Korotkov)
      </para>

      <para>
       Previously, this was only possible via an <acronym>SQL</acronym>
       function or a process signal.
      </para>
     </listitem>

     <listitem>
<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2019-01-14 [bb24439ce] Detach postmaster process from pg_ctl's session at serve
-->

      <para>
       Properly detach the server on <application>pg_ctl</application>
       start (Paul Guo)
      </para>

      <para>
       This prevents later shell activity from interfering with the
       postmaster.
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter_e@gmx.net>
2018-11-07 [3a769d823] pg_upgrade: Allow use of file cloning
-->

      <para>
       Allow <xref linkend="pgupgrade"/> to use the file system cloning
       feature (Peter Eisentraut)
      </para>

      <para>
       The <option>--clone</option> option has the advantages of
       <option>--link</option>, while preventing the old cluster from
       being changed after the new cluster has started.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-12-01 [2d34ad843] Add a - -socketdir option to pg_upgrade.
-->

      <para>
       Allow specification of the <application>pg_upgrade</application>
       socket directory (Daniel Gustafsson)
      </para>

      <para>
       This is controlled by <option>--socketdir</option>;  the default
       is the current directory.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-13 [23bd3cec6] Attempt to identify system timezone by reading /etc/loca
-->

      <para>
       Have <xref linkend="app-initdb"/> determine the local timezone
       from the <filename>/etc/localtime</filename> symbolic link,
       if it exists (Tom Lane)
      </para>

      <para>
       This is more likely to produce the desired time zone string when
       multiple identical time zones exist.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-03-23 [e0090c869] Add option -N/- -no-sync to pg_checksums
-->

      <para>
       Allow <xref linkend="app-pgchecksums"/> to disable fsync operations
       (Michaël Paquier)
      </para>

      <para>
       This is controlled by the <option>--no-sync</option> option.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-07-10 [8a00b96aa] Add pg_rewind - -no-sync
-->

      <para>
       Allow <xref linkend="app-pgrewind"/> to disable fsync operations
       (Michaël Paquier)
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="app-pgdump"><application>pg_dump</application></link>,
     <link linkend="app-pg-dumpall"><application>pg_dumpall</application></link>,
     <link linkend="app-pgrestore"><application>pg_restore</application></link></title>

     <itemizedlist>

      <listitem>
<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2019-03-07 [7e413a0f8] pg_dump: allow multiple rows per insert
-->

       <para>
        Allow control over the number of rows each
        <application>pg_dump</application> <command>INSERT</command>
        statement uses (Surafel Temesgen, David Rowley)
       </para>

       <para>
        The option is <option>--rows-per-insert</option>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Andrew Dunstan <andrew@dunslane.net>
2019-03-01 [f092de050] Add - -exclude-database option to pg_dumpall
-->

       <para>
        Add <option>--exclude-database</option> option to
        <application>pg_dumpall</application> (Andrew Dunstan)
       </para>
      </listitem>

      <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2018-07-13 [387a5cfb9] Add pg_dump - -on-conflict-do-nothing option.
-->

       <para>
        Allow pg_dump to emit <command>INSERT ... ON CONFLICT DO
        NOTHING</command> (Surafel Temesgen)
       </para>

       <para>
        This avoids conflict failures during restore.
        The <application>pg_dump</application> option is
        <option>--on-conflict-do-nothing</option>.
       </para>
      </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-14 [548e50976] Improve parallel scheduling logic in pg_dump/pg_restore.
-->

       <para>
        Decouple the order of parallel <application>pg_dump</application>
        from the order used by <application>pg_restore</application>
        (Tom Lane)
       </para>

       <para>
        This allows <application>pg_restore</application> to perform more
        efficient parallel restores.
       </para>
      </listitem>

      <listitem>
<!--
Author: Andrew Dunstan <andrew@dunslane.net>
2019-02-18 [af25bc03e] Provide an extra-float-digits setting for pg_dump / pg_d
-->

       <para>
        Allow the number of float digits to be specified
        for <application>pg_dump</application> and
        <application>pg_dumpall</application> (Andrew Dunstan)
       </para>

       <para>
        This allows the float digit output to match previous dumps.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-11-16 [4da597edf] Make TupleTableSlots extensible, finish split of
Author: Andres Freund <andres@anarazel.de>
2019-03-06 [8586bf7ed] tableam: introduce table AM infrastructure.
Author: Andres Freund <andres@anarazel.de>
2019-03-06 [3b925e905] tableam: Add pg_dump support.
Author: Andres Freund <andres@anarazel.de>
2019-03-11 [c2fe139c2] tableam: Add and use scan APIs.
Author: Andres Freund <andres@anarazel.de>
2019-03-23 [5db6df0c0] tableam: Add tuple_{insert, delete, update, lock} and us
Author: Andres Freund <andres@anarazel.de>
2019-03-28 [d25f51910] tableam: relation creation, VACUUM FULL/CLUSTER, SET TAB
Author: Andres Freund <andres@anarazel.de>
2019-03-29 [d3a5fc17e] Show table access methods as such in psql's \dA.
Author: Andres Freund <andres@anarazel.de>
2019-03-31 [73c954d24] tableam: sample scan.
Author: Andres Freund <andres@anarazel.de>
2019-03-31 [bfbcad478] tableam: bitmap table scan.
existin
-->

      <para>
       Add <xref linkend="sql-create-access-method"/> command to create
       new table types (Andres Freund, Haribabu Kommi, Álvaro Herrera,
       Alexander Korotkov, Dimitri Golgov)
      </para>

      <para>
       This enables the development of new <link linkend="tableam">table
       access methods</link>, which can optimize storage for different
       use-cases.  The existing <literal>heap</literal> access method
       remains the default.
      </para>
     </listitem>

      <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-02-09 [1fb57af92] Create the infrastructure for planner support functions.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2019-02-09 [a391ff3c3] Build out the planner support function infrastructure.
-->

       <para>
        Add support function capability to improve optimizer estimates,
        inlining, and indexing for functions (Tom Lane)
       </para>

       <para>
        This allows extensions to create planner support functions that
        can provide function-specific selectivity, cost, and row-count
        estimates that can depend on the function's arguments.  Support
        functions can also supply simplified representations and index
        conditions, greatly expanding optimization possibilities.
       </para>
      </listitem>

     <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-12-13 [09568ec3d] Create a separate oid range for oids assigned by genbki.
-->

      <para>
       Reserve a range of oids (9000-9999) to be used for external
       extensions (Andres Freund)
      </para>
     </listitem>

     <listitem>
<!--
Author: Andrew Dunstan <andrew@dunslane.net>
2018-10-02 [a33245a85] Don't build static libraries on Cygwin
-->

      <para>
       Build <productname>Cygwin</productname> binaries using dynamic
       instead of static libraries (Marco Atzeri)
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-01-01 [1707a0d2a] Remove configure switch - -disable-strong-random
-->

      <para>
       Remove <application>configure</application> switch
       <option>--disable-strong-random</option> (Michaël Paquier)
      </para>

      <para>
       A strong random source is now required.
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-09-26 [26e9d4d4e] Convert elog.c's useful_strerror() into a globally-used 
-->

      <para>
       Properly report Winsock errors on
       <productname>Windows</productname> (Tom Lane)
      </para>
     </listitem>

     <listitem>
<!--
Author: Andres Freund <andres@anarazel.de>
2018-08-23 [d9dd406fe] Require C99 (and thus MSCV 2013 upwards).
-->

      <para>
       Require a C99-supported compiler, and <acronym>MSVC</acronym>
       2013 or later on <productname>Windows</productname> (Andres Freund)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Documentation</title>

    <itemizedlist>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-03-27 [ea55aec0a] doc: Add some images
-->

      <para>
       Add images to the <productname>PostgreSQL</productname>
       documentation (Jürgen Purtz)
      </para>
     </listitem>

     <listitem>
<!--
Author: Robert Haas <rhaas@postgresql.org>
2019-03-29 [c900c1526] Warn more strongly about the dangers of exclusive backup
-->

      <para>
       More clearly document the problems of server failure during <link
       linkend="backup-lowlevel-base-backup-exclusive">exclusive base
       backups</link> (David Steele, Robert Haas)
      </para>
     </listitem>

     <listitem>
<!--
Author: Greg Stark <stark@mit.edu>
2018-10-09 [36e9d413a] Add "B" suffix for bytes to docs
-->

      <para>
       Document that the <literal>B</literal>/bytes units can be specified
       for <link linkend="config-setting">server variables</link>
       (Greg Stark)
      </para>
     </listitem>

     <listitem>
<!--
Author: Joe Conway <mail@joeconway.com>
2018-09-24 [c62dd80cd] Document aclitem functions and operators
-->

      <para>
       Add <link linkend="functions-aclitem-op-table">documentation</link>
       for <type>aclitem</type> functions and operators (Fabien Coelho,
       John Naylor)
      </para>
     </listitem>

     <listitem>
<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2019-04-26 [60bbf0753] doc: Update section on NFS
-->

      <para>
       Update documentation on the use of <link
       linkend="creating-cluster-nfs"><acronym>NFS</acronym></link>
       (Peter Eisentraut)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

     <listitem>
<!--
Author: Etsuro Fujita <efujita@postgresql.org>
2019-04-02 [ffab494a4] postgres_fdw: Perform the (ORDERED, NULL) upperrel opera
Author: Etsuro Fujita <efujita@postgresql.org>
2019-04-02 [d50d172e5] postgres_fdw: Perform the (FINAL, NULL) upperrel operati
-->

      <para>
       Allow more <literal>ORDER BY</literal> sorts and
       <literal>LIMIT</literal> clauses to be pushed to
       <application>postgres_fdw</application> foreign tables (Etsuro
       Fujita)
      </para>
     </listitem>

     <listitem>
<!--
Author: Etsuro Fujita <efujita@postgresql.org>
2018-12-04 [f8f6e4467] postgres_fdw: Improve cost and size estimation for aggre
Author: Etsuro Fujita <efujita@postgresql.org>
2019-01-24 [fd1afdbaf] postgres_fdw: Account for tlist eval costs in estimate_p
Author: Etsuro Fujita <efujita@postgresql.org>
2019-05-09 [edbcbe277] postgres_fdw: Fix cost estimation for aggregate pushdown
-->

      <para>
       Improve optimizer cost accounting for pushdown of aggregates to
       <xref linkend="postgres-fdw"/> tables (Etsuro Fujita)
      </para>

      <para>
       This release also improves costing of
       <application>postgres_fdw</application> target list generation.
      </para>
     </listitem>

     <listitem>
<!--
Author: Jeff Davis <jdavis@postgresql.org>
2018-07-08 [a45adc747] Fix WITH CHECK OPTION on views referencing postgres_fdw 
-->

      <para>
       Properly honor <literal>WITH CHECK OPTION</literal> on views
       that reference <application>postgres_fdw</application> tables
       (Etsuro Fujita)
      </para>

      <para>
       While <literal>CHECK OPTION</literal>s on
       <application>postgres_fdw</application> tables are ignored (because
       the reference is foreign), views on such tables are considered
       local, so this release enforces <literal>CHECK OPTION</literal>s
       on them.  Previously, only <command>INSERT</command>s and
       <command>UPDATE</command>s with <literal>RETURNING</literal>
       clauses that returned <literal>CHECK OPTION</literal> values
       were validated.
      </para>
     </listitem>

     <listitem>
<!--
Author: Amit Kapila <akapila@postgresql.org>
2019-01-11 [43cbedab8] Extend pg_stat_statements_reset to reset statistics spec
-->

      <para>
       Allow <link
       linkend="pgstatstatements"><function>pg_stat_statements_reset()</function></link>
       to be more granular (Haribabu Kommi, Amit Kapila)
      </para>

      <para>
       The function now allows reset of statistics for specific databases,
       users, and queries.
      </para>
     </listitem>

     <listitem>
<!--
Author: Andrew Dunstan <andrew@dunslane.net>
2018-07-31 [2d36a5e9d] Provide a log_level setting for auto_explain
-->

      <para>
       Allow control of the <xref linkend="auto-explain"/> log level
       (Tom Dunstan, Andrew Dunstan)
      </para>

      <para>
       The default is <literal>LOG</literal>.
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2019-01-10 [e1c1d5444] Update unaccent rules with release 34 of CLDR for Latin-
-->

      <para>
       Update <application>unaccent</application> rules with new
       punctuation and symbols (Hugh Ranalli, Michaël Paquier)
      </para>
     </listitem>

     <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2019-02-01 [456e3718e] Add combining characters to unaccent.rules.
-->

      <para>
       Allow <xref linkend="unaccent"/> to handle some accents encoded
       as combining characters (Hugh Ranalli)
      </para>
     </listitem>

     <listitem>
<!--
Author: Thomas Munro <tmunro@postgresql.org>
2018-09-02 [5e8d670c3] Add Greek characters to unaccent.rules.
-->

      <para>
       Allow <application>unaccent</application> to remove accents from
       Greek characters (Tasos Maschalidis)
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-23 [48c41fa97] Add a 64-bit hash function for type <type>citext</type>.
-->

      <para>
       Add 64-bit hash function to <xref linkend="citext"/> (Amul Sul)
      </para>

      <para>
       The function <function>citext_hash_extended()</function> also
       requires a seed value.  NO DOCS?
      </para>
     </listitem>

     <listitem>
<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2018-11-23 [eb6f29141] Add a 64-bit hash function for type <application>hstore</application>.
-->

      <para>
       Add 64-bit hash function to <xref linkend="hstore"/> (Amul Sul)
      </para>

      <para>
       The function <function>hstore_hash_extended()</function> also
       requires a seed value.  NO DOCS?
      </para>
     </listitem>

     <listitem>
<!--
Author: Michael Paquier <michael@paquier.xyz>
2018-08-28 [1aaf532de] Rework option set of oid2name
Author: Michael Paquier <michael@paquier.xyz>
2018-08-28 [bfea331a5] Rework option set of vacuumlo
-->

      <para>
       Improve <xref linkend="oid2name"/> and <xref linkend="vacuumlo"/>
       option handling to match other commands (Tatsuro Yamada)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

  </sect2>

  <sect2 id="release-12-acknowledgements">
   <title>Acknowledgments</title>

   <para>
    The following individuals (in alphabetical order) have contributed to this
    release as patch authors, committers, reviewers, testers, or reporters of
    issues.
   </para>

   <simplelist>
    <member></member>
   </simplelist>
  </sect2>

 </sect1>
