 <sect1 id="release-15">
  <title>Release 15</title>

  <formalpara>
   <title>Release date:</title>
   <para>AS OF 2022-06-11</para>
  </formalpara>

  <sect2>
   <title>Overview</title>

   <para>
    <productname>PostgreSQL</productname> 15 contains many new features
    and enhancements, including:
   </para>

   <itemizedlist>
    <listitem><para></para></listitem>
   </itemizedlist>

   <para>
    The above items and other new features of
    <productname>PostgreSQL</productname> 15 are explained in more detail
    in the sections below.
   </para>

  </sect2>

  <sect2>

   <title>Migration to Version 15</title>

    <para>
     A dump/restore using <xref linkend="app-pg-dumpall"/> or use of
     <xref linkend="pgupgrade"/> or logical replication is required for
     those wishing to migrate data from any previous release.  See <xref
     linkend="upgrading"/> for general information on migrating to new
     major releases.
    </para>

    <para>
     Version 15 contains a number of changes that may affect compatibility
     with previous releases.  Observe the following incompatibilities:
    </para>

   <itemizedlist>

<!--
Author: Noah Misch <noah@leadboat.com>
2021-09-09 [b073c3ccd] Revoke PUBLIC CREATE from public schema, now owned by pg
-->

    <listitem>
     <para>
      Remove <literal>PUBLIC</literal> creation permission on the <link
      linkend="ddl-schemas-public"><literal>public</literal> schema</link>
      (Noah Misch)
     </para>

     <para>
      The new default is one of the secure schema usage patterns that <xref
      linkend="ddl-schemas-patterns"/> has recommended since the security
      release for CVE-2018-1058.  The change applies to newly-created
      databases in existing clusters and for new clusters.  Upgrading a
      cluster or restoring a database dump will preserve existing permissions.
     </para>

     <para>
      For existing databases, especially those having multiple users,
      consider revoking <literal>CREATE</literal> permission on
      the <literal>public</literal> schema to adopt this new default.
      For new databases having zero need to defend against insider threats,
      granting <literal>CREATE</literal> permission will yield the behavior
      of prior releases.
     </para>
    </listitem>

<!--
Author: Noah Misch <noah@leadboat.com>
2021-09-09 [b073c3ccd] Revoke PUBLIC CREATE from public schema, now owned by pg
-->

    <listitem>
     <para>
      Change the owner of the <literal>public</literal> schema to
      <literal>pg_database_owner</literal> (Noah Misch)
     </para>

     <para>
      Previously it was the literal user name of the bootstrap superuser.
      Databases restored from previous Postgres releases will be restored
      with their current owner specification.
     </para>
    </listitem>

<!--
Author: Stephen Frost <sfrost@snowman.net>
2022-04-06 [39969e2a1] Remove exclusive backup mode
-->

    <listitem>
     <para>
      Remove long-deprecated exclusive <link
      linkend="backup-base-backup">backup mode</link> (David Steele,
      Nathan Bossart)
     </para>

     <para>
      If the database server stops abruptly while in this mode, the
      server could fail to start.  The non-exclusive backup mode requires
      a continuous database connection during the backup.  Functions
      <function>pg_start_backup()</function>/<function>pg_stop_backup()</function>
      have been renamed to
      <function>pg_backup_start()</function>/<function>pg_backup_stop()</function>,
      and the functions <function>pg_backup_start_time()</function>
      and <function>pg_is_in_backup()</function> have been removed.
     </para>
    </listitem>

<!--
Author: Peter Geoghegan <pg@bowt.ie>
2022-02-16 [8f388f6f5] Increase hash_mem_multiplier default to 2.0.
-->

    <listitem>
     <para>
      Increase <link
      linkend="guc-hash-mem-multiplier"><varname>hash_mem_multiplier</varname></link>
      default to 2.0 (Peter Geoghegan)
     </para>

     <para>
      This allows query hash operations to use double the amount of
      <link linkend="guc-work-mem"><varname>work_mem</varname></link>
      memory as other operations.
     </para>
    </listitem>

<!--
Author: Andres Freund <andres@anarazel.de>
2022-03-07 [76a29adee] plpython: Remove plpythonu, plpython2u and associated tr
-->

    <listitem>
     <para>
      Remove server-side language <link
      linkend="plpython"><literal>plpython2u</literal></link> and generic
      Python language <literal>plpythonu</literal> (Andres Freund)
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-19 [a3d6264bb] interval_out() must be marked STABLE, not IMMUTABLE.
-->

    <listitem>
     <para>
      Mark the <link
      linkend="datatype-datetime"><type>interval</type></link> output
      function as stable, not immutable, since it depends on <link
      linkend="guc-intervalstyle"><varname>IntervalStyle</varname></link>
      (Tom Lane)
     </para>

     <para>
      This will cause the creation of indexes relying on the text output
      of <type>interval</type> values to fail.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-06 [cbe25dcff] Disallow making an empty lexeme via array_to_tsvector().
-->

    <listitem>
     <para>
      Generate an error if <link
      linkend="textsearch-functions-table"><function>array_to_tsvector()</function></link>
      is passed an empty array element (Jean-Christophe Arnu)
     </para>

     <para>
      This is prohibited because lexemes should never be empty.  Users of
      previous Postgres releases should verify that no empty lexemes
      are stored because they can lead to dump/restore failures and
      inconsistent results.
     </para>
    </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-12-06 [e9e63b702] Fix inappropriate uses of PG_GETARG_UINT32()
-->

    <listitem>
     <para>
      Generate an error when <link
      linkend="functions-string-other"><function>chr()</function></link>
      is supplied with a negative argument (Peter Eisentraut)
     </para>
    </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-01-12 [a18b6d2dc] ecpg: Catch zero-length Unicode identifiers correctly
-->

    <listitem>
     <para>
      Prevent Unicode zero-length <link
      linkend="sql-syntax-identifiers">identifiers</link>, e.g., U&amp;""
      (Peter Eisentraut)
     </para>

     <para>
      Non-Unicode zero-length identifiers were already prevented.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-15 [2a712066d] Remove pg_dump's - -no-synchronized-snapshots switch.
-->

    <listitem>
     <para>
      Remove <link
      linkend="sql-syntax-identifiers"><application>pg_dump</application></link>'s
      <option>--no-synchronized-snapshots</option> option since all
      supported server versions support synchronized snapshots (Tom Lane)
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-15 [2523928b2] Reject change of output-column collation in CREATE OR RE
-->

    <listitem>
     <para>
      Prevent <link linkend="sql-createview"><command>CREATE OR REPLACE
      VIEW</command></link> from changing the collation of an output column
      (Tom Lane)
     </para>
    </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-02-16 [2549f0661] Reject trailing junk after numeric literals
-->

    <listitem>
     <para>
      Prevent <link linkend="sql-syntax-constants-numeric">numeric
      literals</link> from having non-numeric trailing characters (Peter
      Eisentraut)
     </para>

     <para>
      Previously literals like <literal>123abc</literal> would be
      interpreted as <literal>123</literal> and <literal>abc</literal>.
     </para>
    </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-03-28 [e26114c81] Make JSON path numeric literals more correct
-->

    <listitem>
     <para>
      Adjust <link linkend="datatype-json"><acronym>JSON</acronym></link>
      numeric literal processing to match the
      <acronym>SQL</acronym>/<acronym>JSON</acronym>-standard (Peter
      Eisentraut)
     </para>

     <para>
      This accepts numeric formats like <literal>.1</literal> and
      <literal>1.</literal>, and disallows trailing junk after numeric
      literals, like <literal>1.type()</literal>.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-03 [591e088dd] Fix portability issues in datetime parsing.
-->

    <listitem>
     <para>
      Improve consistency of <link
      linkend="datatype-datetime">interval</link> parsing with trailing
      periods (Tom Lane)
     </para>

     <para>
      Some platforms disallowed trailing periods.
     </para>
    </listitem>

<!--
Author: Bruce Momjian <bruce@momjian.us>
2021-08-03 [95ab1e0a9] interval:  round values when spilling to months
-->

    <listitem>
     <para>
      When specifying fractional interval values in units greater than
      months, round to the nearest month (Bruce Momjian)
     </para>

     <para>
      For example, report <literal>1.99 years</literal> as <literal>2
      years</literal>, not <literal>1 year 11 months</literal>.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-28 [54bd1e43c] Handle integer overflow in interval justification functi
-->

    <listitem>
     <para>
      Detect integer overflow in <link
      linkend="functions-datetime-table">interval justification
      functions</link> (Joe Koshakow)
     </para>

     <para>
      Specifically, functions <function>justify_interval()</function>,
      <function>justify_hours()</function>, and
      <function>justify_days()</function> are affected.
     </para>
    </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-03-28 [79de9842a] Remove the ability of a role to administer itself.
-->

    <listitem>
     <para>
      Remove the default <link linkend="sql-createrole"><literal>ADMIN
      OPTION</literal></link> privilege a login role has on its own role
      membership (Robert Haas)
     </para>

     <para>
      Previously, login roles could add/remove members of its own role,
      even without <literal>ADMIN OPTION</literal> privilege.
     </para>
    </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2022-01-07 [a2ab9c06e] Respect permissions within logical replication.
-->

    <listitem>
     <para>
      Allow <link linkend="logical-replication">logical replication</link>
      to run as the owner of the subscription (Mark Dilger)
     </para>

     <para>
      Because row-level security policies are not checked, only superusers,
      roles with <literal>bypassrls</literal>, and table owners can
      replicate into tables with row-level security policies.
     </para>
    </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2022-01-08 [96a6f11c0] More cleanup of a2ab9c06ea.
-->

    <listitem>
     <para>
      Prevent <command>UPDATE</command> and <command>DELETE</command>
      <link linkend="logical-replication">logical replication</link>
      operations on tables where the subscription owner does not have
      <command>SELECT</command> permission on the table (Jeff Davis)
     </para>

     <para>
      <command>UPDATE</command> and <command>DELETE</command> perform
      <command>SELECT</command>, so require the subscription owner to
      have table <command>SELECT</command> permission.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-07-27 [48c5c9068] Use the "pg_temp" schema alias in EXPLAIN and related ou
-->

    <listitem>
     <para>
      When <link linkend="sql-explain"><command>EXPLAIN</command></link>
      references the temporary object schema, refer to it as
      <literal>pg_temp</literal> (Amul Sul)
     </para>

     <para>
      Previously the actual schema name was used.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-28 [2e517818f] Fix SPI's handling of errors during transaction commit.
-->

    <listitem>
     <para>
      Modify <link linkend="spi"><acronym>SPI</acronym></link>'s
      <function>SPI_commit()</function> and
      <function>SPI_commit_and_chain()</function> to automatically start
      a new transaction at completion (Peter Eisentraut, Tom Lane)
     </para>

     <para>
      BACKPATCHED?
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-03-24 [ce95c5437] Fix pg_statio_all_tables view for multiple TOAST indexes
-->

    <listitem>
     <para>
      Fix <link
      linkend="monitoring-pg-statio-all-tables-view"><structname>pg_statio_all_tables</structname></link>
      to sum values for the rare case of <acronym>TOAST</acronym> tables
      with multiple indexes (Andrei Zubkov)
     </para>

     <para>
      Previously such cases would have one row for each index.
     </para>
    </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-12-01 [75d22069e] Warning on SET of nonexisting setting with a prefix rese
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-27 [2ed8a8cc5] Rethink handling of settings with a prefix reserved by a
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-21 [88103567c] Disallow setting bogus GUCs within an extension's reserv
-->

    <listitem>
     <para>
      Disallow setting of <link linkend="config-setting">server
      variables</link> matching the prefixes of installed extension
      (Florin Irion, Tom Lane)
     </para>

     <para>
      This also deletes any matching server variables during extension
      load.
     </para>
    </listitem>

<!--
Author: Andres Freund <andres@anarazel.de>
2022-04-06 [6f0cf8787] pgstat: remove stats_temp_directory.
-->

    <listitem>
     <para>
      Remove unnecessary server variable
      <varname>stats_temp_directory</varname> (Andres Freund, Kyotaro
      Horiguchi)
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-28 [3804539e4] Replace random(), pg_erand48(), etc with a better PRNG A
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-12 [d4f109e4a] Doc: update description of random() function.
-->

    <listitem>
     <para>
      Improve the algorithm used to compute <link
      linkend="functions-math-random-table"><function>random()</function></link>
      (Fabien Coelho)
     </para>

     <para>
      This will cause <function>random()</function> to differ from what
      was emitted by prior versions for the same seed values.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-12 [f8abb0f5e] postgres_fdw: suppress casts on constants in limited cas
-->

    <listitem>
     <para>
      Reduce casting of constants in <link
      linkend="postgres-fdw">postgres_fdw</link> queries (Dian Fay)
     </para>

     <para>
      If column types were mismatched between local and remote databases,
      such casting could cause errors.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-14 [fd2abeb7c] Delete contrib/xml2's legacy implementation of xml_is_we
-->

    <listitem>
     <para>
      Remove <link linkend="xml2">xml2</link>'s function
      <function>xml_is_well_formed()</function> (Tom Lane)
     </para>

     <para>
      This function has been implemented in the core backend since
      Postgres 9.1.
     </para>
    </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-07-06 [955b3e0f9] Allow CustomScan providers to say whether they support p
-->

    <listitem>
     <para>
      Allow <link linkend="custom-scan">custom scan providers</link>
      to indicate if they support projections (Sven Klemm)
     </para>

     <para>
      The default is now that custom scan providers are assumed to not
      support projections;  those that do will need to be updated for
      this release.
     </para>
    </listitem>

   </itemizedlist>

  </sect2>

  <sect2>
   <title>Changes</title>

   <para>
    Below you will find a detailed account of the changes between
    <productname>PostgreSQL</productname> 15 and the previous major
    release.
   </para>

   <sect3>
    <title>Server</title>

    <itemizedlist>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-02-14 [37851a8b8] Database-level collation version tracking
-->

     <listitem>
      <para>
       Record and check the collation version of each <link
       linkend="sql-createdatabase">database</link> (Peter Eisentraut)
      </para>

      <para>
       This is designed to detect collation version
       mismatches to avoid data corruption.  Function
       <function>pg_database_collation_actual_version()</function>
       reports the underlying operating system collation version, and
       <command>ALTER DATABASE ...  REFRESH</command> sets the database
       to match the operating system collation version.
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-03-17 [f2553d430] Add option to use ICU as global locale provider
-->

     <listitem>
      <para>
       Allow <link linkend="locale"><acronym>ICU</acronym></link>
       collations to be set as the default for clusters and databases
       (Peter Eisentraut)
      </para>

      <para>
       Previously, only <application>libc</application>-based
       collations could be set at the cluster and database levels.
       <acronym>ICU</acronym> collations were previously limited
       to <link linkend="sql-createcollation"><command>CREATE
       COLLATION</command></link> and referenced by the
       <literal>COLLATE</literal> clause.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-03-29 [a2c84990b] Add system view pg_ident_file_mappings
-->

     <listitem>
      <para>
       Add system view <link
       linkend="view-pg-ident-file-mappings"><structname>pg_ident_file_mappings</structname></link>
       to report <filename>pg_ident.conf</filename> information (Julien
       Rouhaud)
      </para>
     </listitem>

       </itemizedlist>

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

     <itemizedlist>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-08-03 [475dbd0b7] Track a Bitmapset of non-pruned partitions in RelOptInfo
-->

      <listitem>
       <para>
        Improve planning time for queries referencing partitioned tables
        (David Rowley)
       </para>

       <para>
        Specifically this helps if only a small number of the many
        partitions are relevant.
       </para>
      </listitem>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-08-03 [db632fbca] Allow ordered partition scans in more cases
-->

      <listitem>
       <para>
        Allow ordered scans of partitions to avoid sorting in more cases
        (David Rowley)
       </para>

       <para>
        Previously, a partitioned table with a <literal>DEFAULT</literal>
        partition or a <literal>LIST</literal> partition containing
        multiple values could not be used for ordered partition scans.
        Now they can be used if these partitions are pruned.
       </para>
      </listitem>

<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2022-03-20 [ba9a7e392] Enforce foreign key correctly during cross-partition upd
-->

      <listitem>
       <para>
        Improve foreign key behavior of updates on partitioned tables
        that move rows between partitions (Amit Langote)
       </para>

       <para>
        Previously, such updates ran delete actions on the source
        partition and insert actions on the target partition.
        <productname>PostgreSQL</productname> will now run update actions
        on the referenced partition root.
       </para>
      </listitem>

<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2022-04-02 [cfdd03f45] Allow CLUSTER on partitioned tables
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2022-04-14 [3f19e176a] Have CLUSTER ignore partitions not owned by caller
-->

      <listitem>
       <para>
        Allow <link linkend="sql-cluster"><command>CLUSTER</command></link>
        on partitioned tables (Justin Pryzby)
       </para>
      </listitem>

<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2021-07-22 [80ba4bb38] Make ALTER TRIGGER RENAME consistent for partitioned tab
-->

      <listitem>
       <para>
        Fix <link linkend="sql-altertable"><command>ALTER TRIGGER
        RENAME</command></link> on partitioned tables to properly rename
        triggers an all partitions (Arne Roland, Álvaro Herrera)
       </para>

       <para>
        Also prohibit cloned triggers from being renamed.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Indexes</title>

     <itemizedlist>

<!--
Author: Peter Geoghegan <pg@bowt.ie>
2021-10-02 [2903f1404] Enable deduplication in system catalog indexes.
-->

      <listitem>
       <para>
        Allow btree indexes on system and <link
        linkend="storage-toast"><acronym>TOAST</acronym></link>
        tables to efficiently store duplicates (Peter Geoghegan)
       </para>

       <para>
        Previously de-duplication was disabled for these types of indexes.
       </para>
      </listitem>

<!--
Author: Alexander Korotkov <akorotkov@postgresql.org>
2022-02-07 [f1ea98a79] Reduce non-leaf keys overlap in GiST indexes produced by
-->

      <listitem>
       <para>
        Improve lookup performance of <link
        linkend="gist"><acronym>GiST</acronym></link> indexes built using
        sorting (Aliaksandr Kalenik, Sergei Shoulbakov, Andrey Borodin)
       </para>
      </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-02-03 [94aa7cc5f] Add UNIQUE null treatment option
-->

      <listitem>
       <para>
        Allow unique constraints and indexes to treat
        <literal>NULL</literal> values as not distinct (Peter Eisentraut)
       </para>

       <para>
        Previously <literal>NULL</literal> values were always indexed
        as distinct values, but this can now be changed by creating
        constraints and indexes using <literal>UNIQUE NULLS NOT
        DISTINCT</literal>.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-17 [a148f8bc0] Add a planner support function for starts_with().
-->

      <listitem>
       <para>
        Allow <link
        linkend="functions-string-other"><literal>^@</literal></link>
        and <function>starts_with()</function> to use btree indexes if
        using a C collation (Tom Lane)
       </para>

       <para>
        Previously these could only use <link
        linkend="spgist"><acronym>SP-GiST</acronym></link> indexes.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Optimizer</title>

     <itemizedlist>

<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2022-01-16 [269b532ae] Add stxdinherit flag to pg_statistic_ext_data
-->

      <listitem>
       <para>
        Allow <link linkend="sql-createstatistics">extended
        statistics</link> to record statistics for a parent with all its
        children (Tomas Vondra, Justin Pryzby)
       </para>

       <para>
        Regular statistics already tracked parent and parent/all-children
        statistics separately.
       </para>
      </listitem>

<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2022-03-31 [db0d67db2] Optimize order of GROUP BY keys
-->

      <listitem>
       <para>
        Allow <link linkend="queries-group"><literal>GROUP
        BY</literal></link> sorting to optimize column order (Dmitry
        Dolgov, Teodor Sigaev, Tomas Vondra)
       </para>

       <para>
        This optimization can be disabled using the server variable <link
        linkend="guc-enable-groupby-reordering"><varname>enable_group_by_reordering</varname></link>.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-03-24 [0bd7af082] Invent recursive_worktable_factor GUC to replace hard-wi
-->

      <listitem>
       <para>
        Add server variable <link
        linkend="guc-recursive-worktable-factor"><varname>recursive_worktable_factor</varname></link>
        to allow the user to specify the expected recursive query worktable
        size (Simon Riggs)
       </para>

       <para>
        WHAT IS A WORKTABLE?  NOT DEFINED.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-07-07 [29f45e299] Use a hash table to speed up NOT IN(values)
-->

      <listitem>
       <para>
        Allow hash lookup for <link
        linkend="functions-subquery-notin"><literal>NOT IN</literal></link>
        clauses with many constants (David Rowley, James Coleman)
       </para>

       <para>
        Previously the code always sequentially scanned the list of values.
       </para>
      </listitem>

<!--
Author: John Naylor <john.naylor@postgresql.org>
2021-12-20 [911588a3f] Add fast path for validating UTF-8 text
-->

      <listitem>
       <para>
        Improve validation of <acronym>UTF</acronym>-8 text (even if
        only <acronym>ASCII</acronym>) by processing 16 bytes at a time
        (John Naylor, Heikki Linnakangas)
       </para>

       <para>
        This will improve text-heavy operations like <link
        linkend="sql-copy"><command>COPY FROM</command></link>.
       </para>
      </listitem>

<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2021-10-18 [65014000b] Replace polyphase merge algorithm with a simple balanced
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2021-10-25 [166f94377] Clarify the logic in a few places in the new balanced me
-->

      <listitem>
       <para>
        Improve performance for sorts that exceed <link
        linkend="guc-work-mem"><varname>work_mem</varname></link>
        (Heikki Linnakangas)
       </para>

       <para>
        Specifically, switch to a batch sorting algorithm that uses more
        output streams internally.
       </para>
      </listitem>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-07-22 [91e9e89dc] Make nodeSort.c use Datum sorts for single column sorts
Author: David Rowley <drowley@postgresql.org>
2022-04-04 [40af10b57] Use Generation memory contexts to store tuples in sorts
Author: John Naylor <john.naylor@postgresql.org>
2022-04-02 [697492434] Specialize tuplesort routines for different kinds of abb
-->

      <listitem>
       <para>
        Improve performance and reduce memory consumption of in-memory
        sorts (Ronan Dunklau, David Rowley, Thomas Munro, John Naylor)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-06-29 [4035cd5d4] Add support for LZ4 with compression of full-page writes
Author: Michael Paquier <michael@paquier.xyz>
2022-03-11 [e9537321a] Add support for zstd with compression of full-page write
-->

      <listitem>
       <para>
        Allow <acronym>WAL</acronym> <link
        linkend="guc-full-page-writes">full page writes</link> to use
        LZ4 and Zstandard compression (Andrey Borodin, Justin Pryzby)
       </para>

       <para>
        This is controlled by the <link
        linkend="guc-wal-compression"><varname>wal_compression</varname></link>
        server setting.
       </para>
      </listitem>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2021-07-19 [2dbe89057] Support direct I/O on macOS.
-->

      <listitem>
       <para>
        Add <link linkend="guc-wal-sync-method">direct I/O</link> support
        to macOS (Thomas Munro)
       </para>

       <para>
        This only works if <literal>max_wal_senders=0</literal>
        and <literal>wal_level=minimal</literal>, and only for
        <acronym>WAL</acronym>.
       </para>
      </listitem>

<!--
Author: Peter Geoghegan <pg@bowt.ie>
2022-04-03 [0b018faba] Set relfrozenxid to oldest extant XID seen by VACUUM.
-->

      <listitem>
       <para>
        Allow <link linkend="routine-vacuuming">vacuum</link> to be more
        aggressive in setting the oldest frozen and multi transaction id
        (Peter Geoghegan)
       </para>
      </listitem>

<!--
Author: Etsuro Fujita <efujita@postgresql.org>
2022-04-06 [c2bb02bc2] Allow asynchronous execution in more cases.
-->

      <listitem>
       <para>
        Allow a query referencing multiple <link
        linkend="ddl-foreign-data">foreign tables</link> to perform
        parallel foreign table scans in more cases (Andrey Lepikhov,
        Etsuro Fujita)
       </para>
      </listitem>

<!--
Author: David Rowley <drowley@postgresql.org>
2022-04-08 [9d9c02ccd] Teach planner and executor about monotonic window funcs
-->

      <listitem>
       <para>
        Improve the performance of <link linkend="functions-window">window
        functions</link> that use <function>row_number()</function>,
        <function>rank()</function>, and <function>count()</function>
        (David Rowley)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-06 [a82a5eee3] Use ISB as a spin-delay instruction on ARM64.
-->

      <listitem>
       <para>
        Improve the performance of spinlocks on high-core-count ARM64
        systems (Geoffrey Blake)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Monitoring</title>

     <itemizedlist>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2021-12-13 [64da07c41] Default to log_checkpoints=on, log_autovacuum_min_durati
-->

      <listitem>
       <para>
        Enable default logging of checkpoints and slow autovacuum
        operations (Bharath Rupireddy)
       </para>

       <para>
        Specifically, this changes the default of <link
        linkend="guc-log-checkpoints"><varname>log_checkpoints</varname></link>
        to on and <link
        linkend="guc-log-autovacuum-min-duration"><varname>log_autovacuum_min_duration</varname></link>
        to 10 minutes.  This will cause idle servers to generate log
        output, which might cause problems on resource-constrained
        servers with insufficient log file removal.  The defaults should
        be changed in such cases.
       </para>
      </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2021-10-25 [9ce346eab] Report progress of startup operations that take a long t
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2021-11-05 [e543906e2] Document default and changeability of log_startup_progre
-->

      <listitem>
       <para>
        Generate periodic log message during slow server starts (Nitin
        Jadhav, Robert Haas)
       </para>

       <para>
        The messages report the cause of the delay.  The time interval for
        notification is controlled by the new server variable <link
        linkend="guc-log-startup-progress-interval"><varname>log_startup_progress_interval</varname></link>.
       </para>
      </listitem>

<!--
Author: Andres Freund <andres@anarazel.de>
2022-04-06 [5891c7a8e] pgstat: store statistics in shared memory.
Author: Andres Freund <andres@anarazel.de>
2022-04-07 [b3abca681] pgstat: Update docs to match the shared memory stats rea
-->

      <listitem>
       <para>
        Store <link linkend="monitoring-stats">cumulative statistics
        system</link> data in shared memory (Kyotaro Horiguchi, Andres
        Freund, Melanie Plageman)
       </para>

       <para>
        Previously this was updated via <acronym>UDP</acronym> packets,
        stored in the file system, and read by sessions.  There is no
        longer a statistics collector process.
       </para>
      </listitem>

<!--
Author: Peter Geoghegan <pg@bowt.ie>
2022-02-11 [872770fd6] Add VACUUM instrumentation for scanned pages, relfrozenx
Author: Peter Geoghegan <pg@bowt.ie>
2022-03-13 [6e20f4600] VACUUM VERBOSE: tweak scanned_pages logic.
Author: Peter Geoghegan <pg@bowt.ie>
2022-04-15 [bdb71dbe8] VACUUM VERBOSE: Show dead items for an empty table.
-->

      <listitem>
       <para>
        Add additional information to <command>VACUUM VERBOSE</command>
        and autovacuum logging messages (Peter Geoghegan)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-04-08 [efb0ef909] Track I/O timing for temporary file blocks in EXPLAIN (B
-->

      <listitem>
       <para>
        Add <link linkend="sql-explain"><command>EXPLAIN
        (BUFFERS)</command></link> output for temporary file block I/O
        (Masahiko Sawada)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-01-17 [dc686681e] Introduce log_destination=jsonlog
-->

      <listitem>
       <para>
        Allow <link linkend="guc-log-destination">log output</link> in
        <acronym>JSON</acronym> format (Sehrope Sarkuni, Michael Paquier)
       </para>

       <para>
        The new setting is <literal>log_destination=jsonlog</literal>.
       </para>
      </listitem>

<!--
Author: Fujii Masao <fujii@postgresql.org>
2021-09-02 [e04267844] Enhance pg_stat_reset_single_table_counters function.
-->

      <listitem>
       <para>
        Allow <link
        linkend="monitoring-stats-funcs-table"><function>pg_stat_reset_single_table_counters()</function></link>
        to reset the counters of relations shared across all databases
        (B Sadhu, Prasad Patro)
       </para>
      </listitem>

<!--
Author: Fujii Masao <fujii@postgresql.org>
2021-11-22 [1b06d7bac] Report wait events for local shell commands like archive
-->

      <listitem>
       <para>
        Add <link linkend="wait-event-table">wait events</link> for local
        shell commands (Fujii Masao)
       </para>

       <para>
        Specifically the new wait events are related to
        commands <varname>archive_command</varname>,
        <varname>archive_cleanup_command</varname>,
        <varname>restore_command</varname> and
        <varname>recovery_end_command</varname>.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title>Privileges</title>

     <itemizedlist>

<!--
Author: Dean Rasheed <dean.a.rasheed@gmail.com>
2022-03-22 [7faa5fc84] Add support for security invoker views.
-->

      <listitem>
       <para>
        Allow <link linkend="sql-createview">view access</link> to be
        controlled by privileges of the view user (Christoph Heiss)
       </para>

       <para>
        Previously, view access could only be based on the view owner.
       </para>
      </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-28 [7f6772317] Adjust server-side backup to depend on pg_write_server_f
-->

      <listitem>
       <para>
        Allow members of the <link
        linkend="predefined-roles-table"><literal>pg_write_server_files</literal></link>
        predefined role to perform server-side base backups (Dagfinn
        Ilmari Mannsåker)
       </para>

       <para>
        Previously only the superusers could perform such backups.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-06 [a0ffa885e] Allow granting SET and ALTER SYSTEM privileges on GUC pa
-->

      <listitem>
       <para>
        Allow <link linkend="sql-grant"><command>GRANT</command></link>
        to assign permission to change server variables via
        <command>SET</command> and <command>ALTER SYSTEM</command>
        (Mark Dilger)
       </para>

       <para>
        The new function <function>has_parameter_privilege()</function>
        reports on this privilege.
       </para>
      </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2021-11-09 [4168a4745] Add pg_checkpointer predefined role for CHECKPOINT comma
-->

      <listitem>
       <para>
        Add predefined role <link
        linkend="predefined-roles-table"><literal>pg_checkpointer</literal></link>
        that allows members to run <command>CHECKPOINT</command>
        (Jeff Davis)
       </para>

       <para>
        Previously checkpoints could only be run by superusers.
       </para>
      </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2021-10-27 [77ea4f943] Grant memory views to pg_read_all_stats.
-->

      <listitem>
       <para>
        Allow members of the <link
        linkend="predefined-roles-table"><literal>pg_read_all_stats</literal></link>
        predefined role to access the views <link
        linkend="view-pg-backend-memory-contexts"><structname>pg_backend_memory_contexts</structname></link>
        and <link
        linkend="view-pg-shmem-allocations"><structname>pg_shmem_allocations</structname></link>
        (Bharath Rupireddy)
       </para>

       <para>
        Previously these views could only be accessed by superusers.
       </para>
      </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2021-10-26 [f0b051e32] Allow GRANT on pg_log_backend_memory_contexts().
-->

      <listitem>
       <para>
        Allow <link linkend="sql-grant"><command>GRANT</command></link>
        to assign permissions on <link
        linkend="view-pg-backend-memory-contexts"><function>pg_log_backend_memory_contexts()</function></link>
        (Jeff Davis)
       </para>

       <para>
        Previously this function could only be run by superusers.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

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

     <itemizedlist>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-09-08 [bd1788051] Introduce GUC shared_memory_size
Author: Michael Paquier <michael@paquier.xyz>
2021-09-09 [3b231596c] Make shared_memory_size a preset option
-->

      <listitem>
       <para>
        Add server variable <link
        linkend="guc-shared-memory-size"><varname>shared_memory_size</varname></link>
        to report the size of allocated shared memory (Nathan Bossart)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-09-21 [43c1c4f65] Introduce GUC shared_memory_size_in_huge_pages
Author: Michael Paquier <michael@paquier.xyz>
2022-03-24 [bbd4951b7] doc: Improve postgres command for shared_memory_size_in_
-->

      <listitem>
       <para>
        Add server variable <link
        linkend="guc-shared-memory-size-in-huge-pages"><varname>shared_memory_size_in_huge_pages</varname></link>
        to report the number of huge memory pages required (Nathan Bossart)
       </para>

       <para>
        This is only supported on Linux.
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-09-16 [0c39c2920] Support "postgres -C" with runtime-computed GUCs
-->

      <listitem>
       <para>
        Allow <link linkend="app-postgres"><command>postgres
        -C</command></link> to properly report runtime-computed values
        (Nathan Bossart)
       </para>

       <para>
        Previously runtime-computed values <link
        linkend="guc-data-checksums"><varname>data_checksums</varname></link>,
        <link
        linkend="guc-wal-segment-size"><varname>wal_segment_size</varname></link>,
        and <link
        linkend="guc-data-directory-mode"><varname>data_directory_mode</varname></link>
        would report values that would not be accurate on the running
        server.  However, this does not work on a running server.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-11 [dab298471] Add suport for server-side LZ4 base backup compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-03-08 [7cf085f07] Add support for zstd base backup compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-03-30 [51c0d186d] Allow parallel zstd compression when taking a base backu
-->

     <listitem>
      <para>
       Add support for LZ4 and Zstandard compression of server-side <link
       linkend="backup-base-backup">base backups</link> (Jeevan Ladhe,
       Robert Haas)
      </para>
     </listitem>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2021-08-02 [7ff23c6d2] Run checkpointer and bgwriter in crash recovery.
-->

     <listitem>
      <para>
       Run checkpointer and bgwriter during crash recovery (Thomas Munro)
      </para>
     </listitem>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2022-04-07 [5dc0418fa] Prefetch data referenced by the WAL, take II.
-->

     <listitem>
      <para>
       Allow <acronym>WAL</acronym> processing to pre-fetch needed file
       contents (Thomas Munro)
      </para>

      <para>
       This is controlled by the server variable <link
       linkend="guc-recovery-prefetch"><varname>recovery_prefetch</varname></link>.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-03 [5ef1eefd7] Allow archiving via loadable modules.
-->

     <listitem>
      <para>
       Add server variable <link
       linkend="guc-archive-library"><varname>archive_library</varname></link>
       to specify the library to be called for archiving (Nathan Bossart)
      </para>

      <para>
       Previously only shell commands could be called to perform archiving.
      </para>
     </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2021-07-09 [8e7811e95] Eliminate replication protocol error related to IDENTIFY
-->

     <listitem>
      <para>
       No longer require <link
       linkend="protocol-replication"><literal>IDENTIFY_SYSTEM</literal></link>
       to be run before <literal>START_REPLICATION</literal> (Jeff Davis)
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="logical-replication">Logical Replication</link></title>

     <itemizedlist>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2021-10-27 [5a2832465] Allow publishing the tables of schema.
Author: Amit Kapila <akapila@postgresql.org>
2021-12-08 [1a2aaeb0d] Fix changing the ownership of ALL TABLES IN SCHEMA publi
-->

      <listitem>
       <para>
        Allow publication of all tables in a schema (Vignesh C, Hou Zhijie,
        Amit Kapila)
       </para>

       <para>
        For example, this syntax is now supported:  <link
        linkend="sql-createpublication"><command>CREATE PUBLICATION pub1
        FOR ALL TABLES IN SCHEMA s1,s2;</command></link>  <command>ALTER
        PUBLICATION</command> supports a similar syntax.  Tables added
        later to the listed schemas will also be replicated.
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2022-02-22 [52e4f0cd4] Allow specifying row filters for logical replication of
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2022-03-17 [5a0796622] Fix row filters with multiple publications
Author: Amit Kapila <akapila@postgresql.org>
2022-04-18 [676eeb6dd] Add additional documentation for row filters.
-->

      <listitem>
       <para>
        Allow publication content to be filtered using a
        <literal>WHERE</literal> clause (Hou Zhijie, Euler Taveira,
        Peter Smith, Ajin Cherian, Tomas Vondra, Amit Kapila)
       </para>
      </listitem>

<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2022-03-26 [923def9a5] Allow specifying column lists for logical replication
-->

      <listitem>
       <para>
        Allow <link linkend="sql-createpublication">publications</link> to
        be restricted to specific columns (Tomas Vondra, Álvaro Herrera,
        Rahila Syed)
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2022-03-22 [208c5d65b] Add ALTER SUBSCRIPTION ... SKIP.
-->

      <listitem>
       <para>
        Allow skipping of transactions on a subscriber using <link
        linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION
        ... SKIP</command></link> (Masahiko Sawada)
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2021-07-14 [a8fd13cab] Add support for prepared transactions to built-in logica
Author: Amit Kapila <akapila@postgresql.org>
2021-08-04 [63cf61cde] Add prepare API support for streaming transactions in lo
-->

      <listitem>
       <para>
        Add support for prepared transactions to built-in logical
        replication (Peter Smith, Ajin Cherian, Amit Kapila, Nikhil
        Sontakke, Stas Kelvich)
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2021-06-30 [cda03cfed] Allow enabling two-phase option via replication protocol
-->

      <listitem>
       <para>
        Add two-phase information to the logical replication stream
        (Ajin Cherian)
       </para>

       <para>
        The new <link
        linkend="protocol-replication"><literal>CREATE_REPLICATION_SLOT</literal></link>
        option is called <literal>TWO_PHASE</literal>.
        <application>pg_recvlogical</application> now supports a new
        <option>--two-phase</option> option during slot creation.
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2022-03-30 [d5a9d86d8] Skip empty transactions for logical replication.
-->

      <listitem>
       <para>
        Prevent logical replication of empty transactions (Ajin Cherian,
        Hou Zhijie, Euler Taveira)
       </para>

       <para>
        Previously, write transactions would send empty transactions to
        subscribers if subscribed tables were not modified.
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-11-23 [1922d7c6e] Add SQL functions to monitor the directory contents of r
-->

      <listitem>
       <para>
        Add <acronym>SQL</acronym> functions to monitor the directory
        contents of logical replication slots (Bharath Rupireddy)
       </para>

       <para>
        Specifically, the functions are <link
        linkend="functions-admin-genfile-table"><function>pg_ls_logicalsnapdir()</function></link>,
        <function>pg_ls_logicalmapdir()</function>, and
        <function>pg_ls_replslotdir()</function>.  They can be run by
        members of the predefined <literal>pg_monitor</literal> role.
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2022-03-14 [705e20f85] Optionally disable subscriptions on error.
-->

      <listitem>
       <para>
        Allow subscribers to stop the application of logical replication changes on error
        (Osumi Takamichi, Mark Dilger)
       </para>

       <para>
        This is enabled with the subscriber option <link
        linkend="sql-createsubscription"><literal>disable_on_error</literal></link>
        and avoids possible infinite error loops during stream application.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-02 [f3d4019da] Ensure consistent logical replication of datetime and fl
-->

      <listitem>
       <para>
        Adjust subscriber server variables to match the publisher so
        datetime and float8 values are interpreted consistently (Japin Li)
       </para>

       <para>
        Some publishers might be relying on inconsistent behavior.
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2021-11-30 [8d74fc96d] Add a view to show the stats of subscription workers.
Author: Amit Kapila <akapila@postgresql.org>
2022-03-01 [7a8507329] Reconsider pg_stat_subscription_workers view.
-->

      <listitem>
       <para>
        Add system view <link
        linkend="monitoring-pg-stat-subscription-stats"><structname>pg_stat_subscription_stats</structname></link>
        to report on subscriber activity (Masahiko Sawada)
       </para>

       <para>
        The new function <link
        linkend="monitoring-stats-functions"><function>pg_stat_reset_subscription_stats()</function></link>
        allows the resetting of subscriber statistics.
       </para>
      </listitem>

<!--
Author: Amit Kapila <akapila@postgresql.org>
2021-12-08 [a61bff2bf] De-duplicate the result of pg_publication_tables view.
-->

      <listitem>
       <para>
        Remove incorrect duplicate partitions in system view <link
        linkend="view-pg-publication-tables"><structname>pg_publication_tables</structname></link>
        (Hou Zhijie)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title><link linkend="sql-select"><command>SELECT</command></link>, <link linkend="sql-insert"><command>INSERT</command></link></title>

    <itemizedlist>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-08-22 [22c4e88eb] Allow parallel DISTINCT
-->

     <listitem>
      <para>
       Allow <command>SELECT DISTINCT</command> to be parallelized
       (David Rowley)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2022-03-28 [7103ebb7a] Add support for MERGE SQL command
-->

     <listitem>
      <para>
       Add <acronym>SQL</acronym> <command>MERGE</command> command to
       adjust one table to match another (Simon Riggs, Pavan Deolasee,
       Álvaro Herrera, Amit Langote)
      </para>

      <para>
       This is similar to <command>INSERT ... ON CONFLICT</command>
       but more batch-oriented.
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-01-28 [43f33dc01] Add HEADER support to COPY text format
Author: Peter Eisentraut <peter@eisentraut.org>
2022-03-30 [072132f04] Add header matching mode to COPY FROM
-->

     <listitem>
      <para>
       Add support for <literal>HEADER</literal> option in <link
       linkend="sql-copy"><command>COPY</command></link> text format
       (Rémi Lapeyre)
      </para>

      <para>
       The new option causes the column names to be output, and optionally
       verified on input.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-03-29 [9c08aea6a] Add new block-by-block strategy for CREATE DATABASE.
-->

     <listitem>
      <para>
       Add new <acronym>WAL</acronym>-logged method for <link
       linkend="sql-createdatabase">database creation</link> (Dilip Kumar)
      </para>

      <para>
       This is the new default for database creation and avoids the need
       for checkpoints during database creation; the old method is still
       available.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-24 [aa0105141] pg_upgrade: Preserve database OIDs.
-->

     <listitem>
      <para>
       Allow <link linkend="sql-createdatabase"><command>CREATE
       DATABASE</command></link> to set the database <acronym>OID</acronym>
       (Shruthi KC, Antonin Houska)
      </para>
     </listitem>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2022-02-12 [4eb217631] Fix DROP {DATABASE,TABLESPACE} on Windows.
-->

     <listitem>
      <para>
       Prevent <link linkend="sql-dropdatabase"><command>DROP
       DATABASE</command></link>, <link
       linkend="sql-droptablespace"><command>DROP
       TABLESPACE</command></link>, and <link
       linkend="sql-alterdatabase"><command>ALTER DATABASE SET
       TABLESPACE</command></link> from occasionally failing during
       concurrent use on Windows (Thomas Munro)
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-12-08 [d6f96ed94] Allow specifying column list for foreign key ON DELETE S
-->

     <listitem>
      <para>
       Allow foreign key <link linkend="ddl-constraints-fk"><literal>ON
       DELETE SET</literal></link> actions to affect only specified columns
       (Paul Martinez)
      </para>

      <para>
       Previously, all of the columns in the foreign key were always
       affected.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-07-28 [b0483263d] Add support for SET ACCESS METHOD in ALTER TABLE
-->

     <listitem>
      <para>
       Allow <link linkend="sql-altertable"><command>ALTER
       TABLE</command></link> to modify a table's <literal>ACCESS
       METHOD</literal> (Justin Pryzby, Jeff Davis)
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-08-10 [7b565843a] Add call to object access hook at the end of table rewri
-->

     <listitem>
      <para>
       Properly call object access hooks when <link
       linkend="sql-altertable"><command>ALTER TABLE</command></link>
       causes table rewrites (Michael Paquier)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Dean Rasheed <dean.a.rasheed@gmail.com>
2021-07-26 [085f931f5] Allow numeric scale to be negative or greater than preci
-->

     <listitem>
      <para>
       Allow <link linkend="datatype-numeric"><type>numeric</type></link>
       scale to be negative or greater than precision (Dean Rasheed,
       Tom Lane)
      </para>

      <para>
       This allows rounding of values to the left of the decimal point,
       e.g., <literal>'1234'::numeric(4, -2)</literal> returns 1200.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-02 [e39f99046] Fix overflow hazards in interval input and output conver
-->

     <listitem>
      <para>
       Improve overflow detection when casting values to <link
       linkend="datatype-datetime">interval</link> (Joe Koshakow)
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-04-07 [344d62fb9] Unlogged sequences
-->

     <listitem>
      <para>
       Allow the creation of unlogged <link
       linkend="sql-createsequence">sequences</link> (Peter Eisentraut)
      </para>
     </listitem>

<!--
Author: John Naylor <john.naylor@postgresql.org>
2021-08-26 [bab982161] Update display widths as part of updating Unicode
Author: Peter Eisentraut <peter@eisentraut.org>
2021-09-15 [f7e56f1f5] Update Unicode data to Unicode 14.0.0
-->

     <listitem>
      <para>
       Update the display width information of modern Unicode characters,
       like emojis (Jacob Champion)
      </para>

      <para>
       Also update from Unicode 5.0 to 14.0.0.  There is now an automated
       way to keep Postgres updated with Unicode releases.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

   <sect3>
    <title>Functions</title>

    <itemizedlist>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-03-30 [7ae1619bc] Add range_agg with multirange inputs
-->

     <listitem>
      <para>
       Add multirange input to <link
       linkend="functions-aggregate-table"><function>range_agg()</function></link>
       (Paul Jungwirth)
      </para>
     </listitem>

<!--
Author: Fujii Masao <fujii@postgresql.org>
2022-02-10 [400fc6b64] Add min() and max() aggregates for xid8.
-->

     <listitem>
      <para>
       Add <link linkend="tutorial-agg"><function>MIN()</function></link>
       and <function>MAX()</function> aggregates for the <link
       linkend="datatype-int"><type>xid8</type></link> data type (Ken Kato)
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-08-03 [642433707] Add assorted new regexp_xxx SQL functions.
-->

     <listitem>
      <para>
       Add regular expression functions for compatibility with other
       relational systems (Gilles Darold, Tom Lane)
      </para>

      <para>
       Specifically, the new functions are <link
       linkend="functions-string-other"><function>regexp_count()</function></link>,
       <function>regexp_instr()</function>,
       <function>regexp_like()</function>, and
       <function>regexp_substr()</function>.  Some new optional arguments
       were also added to <function>regexp_replace()</function>.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-13 [c5c192d7b] Implement poly_distance().
-->

     <listitem>
      <para>
       Add the ability to compute the distance between <link
       linkend="datatype-polygon"><type>polygons</type></link> (Tom Lane)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-03-14 [9dde82899] Support "of", "tzh", and "tzm" format codes.
-->

     <listitem>
      <para>
       Add <link
       linkend="functions-formatting-table"><function>to_char()</function></link>
       format codes <literal>of</literal>, <literal>tzh</literal>, and
       <literal>tzm</literal> format codes (Nitin Jadhav)
      </para>

      <para>
       The upper-case versions of these were already supported.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-09-06 [388e71af8] Make timetz_zone() stable, and correct a bug for DYNTZ a
-->

     <listitem>
      <para>
       Improve the optimization of <function>timetz_zone()</function> by
       stabilizing its value at transaction start (Aleksander Alekseev,
       Tom Lane)
      </para>

      <para>
       HOW IS THIS USED?
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-11-06 [cbe25dcff] Disallow making an empty lexeme via array_to_tsvector().
-->

     <listitem>
      <para>
       Allow <function>tsvector_delete_arr()</function> and
       <function>tsvector_setweight_by_filter()</function> to accept
       empty array elements (Jean-Christophe Arnu)
      </para>

      <para>
       These lexemes are not stored so the acceptance of empty array
       elements is not a problem.  NOT DOCUMENTED, USER API?
      </para>
     </listitem>

<!--
Author: David Rowley <drowley@postgresql.org>
2021-07-09 [ca2e4472b] Teach pg_size_pretty and pg_size_bytes about petabytes
-->

     <listitem>
      <para>
       Add support for petabyte units to <link
       linkend="functions-admin-dbsize"><function>pg_size_pretty()</function></link>
       and <function>pg_size_bytes()</function> (David Christensen)
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-07-27 [024515cac] In event triggers, use "pg_temp" only for our own temp s
-->

     <listitem>
      <para>
       Change <link
       linkend="pg-event-trigger-ddl-command-end-functions"><function>pg_event_trigger_ddl_commands()</function></link>
       to output references to non-local temporary schemas using the
       actual schema name (Tom Lane)
      </para>

      <para>
       Previously this function referred to temporary schemas as
       <literal>pg_temp</literal>.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-30 [ccd10a9bf] Tighten enforcement of variable CONSTANT markings in plp
-->

     <listitem>
      <para>
       Fix enforcement of PL/pgSQL variable <literal>CONSTANT</literal>
       markings (Tom Lane)
      </para>

      <para>
       Previously, a variable used as a <link
       linkend="plpgsql-statements-calling-procedure"><command>CALL</command></link>
       output parameter or refcursor <command>OPEN</command> variable
       would not enforce <literal>CONSTANT</literal>.
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-04-01 [c1932e542] libpq: Allow IP address SANs in server certificates
-->

     <listitem>
      <para>
       Allow <acronym>IP</acronym> address matching against a server
       certificate's Subject Alternative Name (Jacob Champion)
      </para>
     </listitem>

<!--
Author: Daniel Gustafsson <dgustafsson@postgresql.org>
2022-03-29 [ebc8b7d44] Enable SSL library detection via PQsslAttribute()
-->

     <listitem>
      <para>
       Allow <function>PQsslAttribute()</function> to report the
       <acronym>SSL</acronym> library type without requiring a libpq
       connection (Jacob Champion)
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-18 [5987feb70] Make PQcancel use the PGconn's tcp_user_timeout and keep
-->

     <listitem>
      <para>
       Change query cancellations sent by the client to use the same
       <acronym>TCP</acronym> settings as normal client connections
       (Jelte Fennema)
      </para>

      <para>
       This allows configured <acronym>TCP</acronym> timeouts to apply
       to query cancel connections.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-18 [ce1e7a2f7] Don't let libpq "event" procs break the state of PGresul
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-18 [2e372869a] Don't let libpq PGEVT_CONNRESET callbacks break a PGconn
-->

     <listitem>
      <para>
       Prevent libpq event callback failures from forcing an error result
       (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-09 [376ce3e40] Prefer $HOME when looking up the current user's home dir
-->

     <listitem>
      <para>
       On Unix platforms, have client applications like <link
       linkend="app-psql"><application>psql</application></link>
       check <envar>HOME</envar> environment variable for the user's
       home directory before checking the operating system definition
       (Anders Kaseorg)
      </para>
     </listitem>

    </itemizedlist>

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

      <itemizedlist>

<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2021-07-14 [eec57115e] In psql \copy from, send data to server in larger chunks
-->

       <listitem>
        <para>
        Improve performance of <application>psql</application>'s \copy
        command (Heikki Linnakangas)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-20 [33d3eeadb] Add a \getenv command to psql.
-->

      <listitem>
       <para>
        Add <application>psql</application> command \getenv
        to assign the value of an environment variable to a
        <application>psql</application> variable (Tom Lane)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-06 [328dfbdab] Extend psql's \lo_list/\dl to be able to print large obj
-->

      <listitem>
       <para>
        Add '+' option to <application>psql</application>'s
        <literal>\lo_list</literal>/<literal>\dl</literal> to show object
        privileges (Pavel Luzanov)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-07 [3e707fbb4] psql: add \dconfig command to show server's configuratio
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-11 [5e70d8b5d] Tweak the default behavior of psql's \dconfig.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-13 [139d46ee2] Further tweak the default behavior of psql's \dconfig.
-->

      <listitem>
       <para>
        Add <application>psql</application> \dconfig to report server
        variables (Mark Dilger, Tom Lane)
       </para>

       <para>
        This is similar to the server-side <command>SHOW</command>
        command but can process patterns.
       </para>
      </listitem>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2021-07-13 [7c09d2797] Add PSQL_WATCH_PAGER for psql's \watch command.
-->

      <listitem>
       <para>
        Add pager option for <application>psql</application>'s \watch
        command (Pavel Stehule, Thomas Munro)
       </para>

       <para>
        This is only supported on Unix, and is controlled by
        <envar>PSQL_WATCH_PAGER</envar>.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-01 [83884682f] psql: include intra-query "- -" comments in what's sent t
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-01 [c2f654930] psql: treat "- -" comments between queries as separate hi
-->

      <listitem>
       <para>
        Have <application>psql</application> send intra-query double-hyphen
        comments to the server (Tom Lane, Greg Nancarrow)
       </para>

       <para>
        Previously such comments were removed from the query
        before being sent.  Double-hyphen comments that are before
        query text are not sent, and are not recorded as separate
        <application>psql</application> history entries.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-01 [3d858af07] psql: initialize comment-begin setting to a useful value
-->

      <listitem>
       <para>
        Adjust <application>psql</application>'s readline meta-# to insert
        a double-hyphen comment marker (Tom Lane)
       </para>

       <para>
        Previously an unhelpful pound marker was inserted.
       </para>
      </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2022-04-04 [7844c9918] psql: Show all query results by default
-->

      <listitem>
       <para>
        Have <application>psql</application> output all results if multiple
        queries are passed to the server at once (Fabien Coelho)
       </para>

       <para>
        This can be disabled by setting <envar>SHOW_ALL_RESULTS</envar>.
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-08-10 [e2ce88b58] Add tab completion for DECLARE .. ASENSITIVE in psql
Author: Michael Paquier <michael@paquier.xyz>
2021-08-25 [346511313] Add tab completion for EXPLAIN .. EXECUTE in psql
Author: Michael Paquier <michael@paquier.xyz>
2021-08-30 [d3fa87657] Add more tab completion support for ALTER TABLE ADD in p
Author: Michael Paquier <michael@paquier.xyz>
2021-08-31 [f2bbadce6] Add tab completion for data types after ALTER TABLE ADD
Author: Fujii Masao <fujii@postgresql.org>
2021-09-01 [b0c066297] Improve tab-completion for CREATE PUBLICATION.
Author: Fujii Masao <fujii@postgresql.org>
2021-10-05 [0b0d277c3] psql: Improve tab-completion for LOCK TABLE.
Author: Michael Paquier <michael@paquier.xyz>
2021-11-05 [a5b336b8b] Improve psql tab completion for COMMENT
Author: Michael Paquier <michael@paquier.xyz>
2021-11-19 [0cd6d3b3c] Improve psql tab completion for transforms, domains and
Author: Michael Paquier <michael@paquier.xyz>
2021-11-29 [f44ceb46e] Improve psql tab completion for views, FDWs, sequences a
Author: Michael Paquier <michael@paquier.xyz>
2021-12-01 [9270778f4] Improve psql tab completion for various DROP commands
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-03 [dfe67c0e8] Tab completion: don't offer valid constraints in VALIDAT
Author: Fujii Masao <fujii@postgresql.org>
2022-01-15 [74527c3e0] Add tab-completion for CREATE FOREIGN TABLE.
Author: Peter Eisentraut <peter@eisentraut.org>
2022-01-27 [fefce9ef9] psql: Add tab completion for ALTER COLLATION / REFRESH V
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
2022-01-28 [95787e849] Tab-complete ALTER PUBLICATION ADD TABLE with list of ta
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-30 [02b8048ba] psql: improve tab-complete's handling of variant SQL nam
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-01 [020258fbd] Treat case of tab-completion keywords a bit more careful
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-02-09 [f0cd9097c] Further tweaks for psql's new tab-completion logic.
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-03-20 [7fa3db367] psql: handle tab completion of timezone names after "SET
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2022-03-25 [2d2232933] Update tab-completion for CREATE PUBLICATION with sequen
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-04-13 [b5607b074] Fix case sensitivity in psql's tab completion for GUC na
-->

      <listitem>
       <para>
        Improve <application>psql</application>'s tab completion (Shinya
        Kato, Dagfinn Ilmari Mannsåker, Peter Smith, Koyu Tanigawa,
        Ken Kato, David Fetter, Haiying Tang, Peter Eisentraut, Álvaro
        Herrera, Tom Lane, Masahiko Sawada)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-16 [cf0cab868] Remove psql support for server versions preceding 9.2.
-->

      <listitem>
       <para>
        Limit support of <application>psql</application> to servers running
        <productname>PostgreSQL</productname> 9.2 and later (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

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

    <itemizedlist>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-20 [3500ccc39] Support base backup targets.
-->

     <listitem>
      <para>
       Add new <link
       linkend="app-pgbasebackup"><application>pg_basebackup</application></link>
       option <option>--target</option> to control the base backup location
       (Robert Haas)
      </para>

      <para>
       New output options are <literal>server</literal> to write the
       backup locally and <literal>blackhole</literal> to discard the
       backup (for testing).
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-11 [751b8d23b] pg_basebackup: Allow client-side LZ4 (de)compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-03-08 [7cf085f07] Add support for zstd base backup compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-01-24 [0ad803291] Server-side gzip compression.
-->

     <listitem>
      <para>
       Allow <application>pg_basebackup</application> to do server-side
       gzip, LZ4, and Zstandard compression and client-side LZ4 and
       Zstandard compression of base backup files (Dipesh Pandit,
       Jeevan Ladhe)
      </para>

      <para>
       Client-side <literal>gzip</literal> compression was already
       supported.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-28 [d45099425] Allow server-side compression to be used with -Fp.
-->

     <listitem>
      <para>
       Allow <application>pg_basebackup</application> to compress on
       the server side and decompress on the client side before storage
       (Dipesh Pandit)
      </para>

      <para>
       This is accomplished by specifying compression on the server side
       and plain output format.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-01-21 [5c649fe15] Extend the options of pg_basebackup to control compressi
Author: Robert Haas <rhaas@postgresql.org>
2022-01-24 [0ad803291] Server-side gzip compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-01-25 [e1f860f13] Tidy up a few cosmetic issues related to pg_basebackup.
-->

     <listitem>
      <para>
       Allow <application>pg_basebackup</application>'s
       <option>--compress</option> option to control the compression
       location (server or client), compression method, and compression
       options (Michael Paquier, Robert Haas)
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-11-05 [babbbb595] Add support for LZ4 compression in pg_receivewal
Author: Michael Paquier <michael@paquier.xyz>
2022-04-13 [042a923ad] Rework compression options of pg_receivewal
-->

     <listitem>
      <para>
       Add the LZ4 compression method to <link
       linkend="app-pgreceivewal"><application>pg_receivewal</application></link>
       (Georgios Kokolatos)
      </para>

      <para>
       This is enabled via <literal>--compress=lz4</literal> and requires
       binaries to be built using <option>--with-lz4</option>.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-11-04 [d62bcc8b0] Rework compression options of pg_receivewal
-->

     <listitem>
      <para>
       Add additional capabilities to
       <application>pg_receivewal</application>'s
       <option>--compress</option> option (Georgios Kokolatos)
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-10-26 [f61e1dd2c] Allow pg_receivewal to stream from a slot's restart LSN
-->

     <listitem>
      <para>
       Improve <application>pg_receivewal</application>'s ability to
       restart at the proper <acronym>WAL</acronym> location (Ronan
       Dunklau)
      </para>

      <para>
       Previously, <application>pg_receivewal</application> would start
       based on the <acronym>WAL</acronym> file stored in the local archive
       directory, or at the sending server's current <acronym>WAL</acronym>
       flush location.  With this change, if the sending server is running
       Postgres 15 or later, the local archive directory is empty, and
       a replication slot is specified, the replication slot's restart
       point will be used.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-04-07 [0d5c38757] Add option - -config-file to pg_rewind
-->

     <listitem>
      <para>
       Add <application>pg_rewind</application> option
       <option>--config-file</option> to simplify use when server
       configuration files are stored outside the data directory (Gunnar
       Bluth)
      </para>
     </listitem>

<!--
Author: Tatsuo Ishii <ishii@postgresql.org>
2022-03-23 [4a39f87ac] Allow pgbench to retry in some cases.
-->

     <listitem>
      <para>
       Allow <link
       linkend="pgbench"><application>pgbench</application></link> to
       retry after serialization and deadlock failures (Yugo Nagata,
       Marina Polyakova)
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="app-pgdump"><application>pg_dump</application></link></title>

     <itemizedlist>

<!--
Author: Noah Misch <noah@leadboat.com>
2021-06-28 [a7a7be1f2] Dump public schema ownership and security labels.
Author: Noah Misch <noah@leadboat.com>
2021-06-28 [7ac10f692] Dump COMMENT ON SCHEMA public.
-->

      <listitem>
       <para>
        Have <application>pg_dump</application> dump
        <literal>public</literal> schema ownership changes and security
        labels (Noah Misch)
       </para>

       <para>
        It also dumps <literal>public</literal> schema comments.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-06 [989596152] Avoid per-object queries in performance-critical paths i
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-06 [be85727a3] Use PREPARE/EXECUTE for repetitive per-object queries in
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-31 [d5e8930f5] pg_dump: minor performance improvements from eliminating
-->

      <listitem>
       <para>
        Improve performance of dumping databases with many objects
        (Tom Lane)
       </para>

       <para>
        This will also improve the performance of <link
        linkend="pgupgrade"><application>pg_upgrade</application></link>.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-06 [65aaed22a] Account for TOAST data while scheduling parallel dumps.
-->

      <listitem>
       <para>
        Improve the parallel <application>pg_dump</application> performance
        of <acronym>TOAST</acronym> tables (Tom Lane)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-01-17 [215862886] Add support for - -no-table-access-method in pg_{dump,dum
-->

      <listitem>
       <para>
        Add dump/restore option <option>--no-table-access-method</option>
        to force restore to only use the default table access method
        (Justin Pryzby)
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-14 [30e7c175b] Remove pg_dump/pg_dumpall support for dumping from pre-9
-->

      <listitem>
       <para>
        Limit support of <application>pg_dump</application> and <link
        linkend="app-pg-dumpall"><application>pg_dumpall</application></link>
        to servers running <productname>PostgreSQL</productname> 9.2 and
        later (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="pgupgrade"><application>pg_upgrade</application></link></title>

     <itemizedlist>

<!--
Author: Andres Freund <andres@anarazel.de>
2022-02-21 [27b02e070] pg_upgrade: Don't print progress status when output is n
-->

      <listitem>
       <para>
        Disable default status reporting during
        <application>pg_upgrade</application> operation if the output is
        not a terminal (Andres Freund)
       </para>

       <para>
        The status reporting output can be enabled for non-tty usage by
        using <option>--verbose</option>.
       </para>
      </listitem>

<!--
Author: Daniel Gustafsson <dgustafsson@postgresql.org>
2022-03-24 [26ebb0e28] List offending databases in pg_upgrade datallowconn chec
-->

      <listitem>
       <para>
        Have <application>pg_upgrade</application> report all databases
        with invalid connection settings (Jeevan Ladhe)
       </para>

       <para>
        Previously only the first database with an invalid connection
        setting was reported.
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-02-06 [38bfae365] pg_upgrade: Move all the files generated internally to a
Author: Michael Paquier <michael@paquier.xyz>
2022-02-15 [a00849630] Fix thinko with subdirectories generated by pg_upgrade f
-->

      <listitem>
       <para>
        Store <application>pg_upgrade</application>
        temporary files in a new cluster subdirectory called
        <filename>pg_upgrade_output.d</filename> (Justin Pryzby)
       </para>

       <para>
        Previously temporary files were stored in the current directory.
       </para>
      </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-17 [9a974cbcb] pg_upgrade: Preserve relfilenodes and tablespace OIDs.
Author: Robert Haas <rhaas@postgresql.org>
2022-01-24 [aa0105141] pg_upgrade: Preserve database OIDs.
-->

      <listitem>
       <para>
        Have <application>pg_upgrade</application> preserve tablespace
        and database OIDs, and relfilenodes between old and new clusters
        (Shruthi KC, Antonin Houska)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-12-18 [3d5ffccb6] Add option -N/- -no-sync to pg_upgrade
-->

      <listitem>
       <para>
        Add a <option>--no-sync</option> option to
        <application>pg_upgrade</application> (Michael Paquier)
       </para>

       <para>
        This useful only for testing.
       </para>
      </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-14 [e469f0aaf] Remove pg_upgrade support for upgrading from pre-9.2 ser
-->

      <listitem>
       <para>
        Limit support of <application>pg_upgrade</application> to old
        servers running <productname>PostgreSQL</productname> 9.2 and later
        (Tom Lane)
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

    <sect4>
     <title><link linkend="pgwaldump"><application>pg_waldump</application></link></title>

     <itemizedlist>

<!--
Author: Thomas Munro <tmunro@postgresql.org>
2022-03-24 [127aea2a6] Add additional filtering options to pg_waldump.
Author: Thomas Munro <tmunro@postgresql.org>
2022-03-25 [52b556843] Improve command line options for pg_waldump.
-->

      <listitem>
       <para>
        Allow <application>pg_waldump</application> to be filtered by
        relation file node, block number, fork number, and full page images
        (David Christensen, Thomas Munro)
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-12-02 [f2c52eeba] pg_waldump: Emit stats summary when interrupted by SIGIN
-->

      <listitem>
       <para>
        Have <application>pg_waldump</application> report statistics
        before an interrupted exit (Bharath Rupireddy)
       </para>

       <para>
        For example, issuing a control-C in a terminal running
        <command>pg_waldump --stats --follow</command> will report the
        current statistics before exiting.  This does not work on Windows.
       </para>
      </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-12-13 [c8b733c4c] Improve description of some WAL records with transaction
-->

      <listitem>
       <para>
        Improve descriptions of some transaction <acronym>WAL</acronym>
        records reported by <application>pg_waldump</application>
        (Masahiko Sawada, Michael Paquier)
       </para>
      </listitem>

<!--
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
2021-07-01 [c8bf5098c] Allow specifying pg_waldump - -rmgr option multiple times
-->

      <listitem>
       <para>
        Allow <application>pg_waldump</application> to dump information
        about multiple resource managers (Heikki Linnakangas)
       </para>

       <para>
        This is enabled by specifying the <option>--rmgr</option> option
        multiple times.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

   <sect3>
    <title>Documentation</title>

    <itemizedlist>

<!--
Author: Fujii Masao <fujii@postgresql.org>
2021-10-05 [f6b5d05ba] doc: Document pg_encoding_to_char() and pg_char_to_encod
-->

     <listitem>
      <para>
       Add documentation for <link
       linkend="functions-info-catalog-table"><function>pg_encoding_to_char()</function></link>
       and <function>pg_char_to_encoding()</function> (Ian Lawrence
       Barwick)
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-10-09 [2ae5d72f0] Doc: improve documentation for ^@ starts-with operator.
-->

     <listitem>
      <para>
       Document the <link
       linkend="functions-string-other"><literal>^@</literal></link>
       starts-with operator (Tom Lane)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Andres Freund <andres@anarazel.de>
2021-12-30 [93d973494] ci: Add continuous integration for github repositories v
-->

     <listitem>
      <para>
       Add support for continuous integration testing using cirrus-ci
       (Andres Freund, Thomas Munro, Melanie Plageman)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-18 [6c417bbcc] Add support for building with ZSTD.
-->

     <listitem>
      <para>
       Add configure option <link
       linkend="configure-options-features"><option>--with-zstd</option></link>
       to enable Zstandard builds (Jeevan Ladhe, Robert Haas, Michael
       Paquier)
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-11-22 [d6d1dfcc9] Add ABI extra field to fmgr magic block
-->

     <listitem>
      <para>
       Add module field which can be customized for non-community
       <productname>PostgreSQL</productname> distributions (Peter
       Eisentraut)
      </para>

      <para>
       A module field mismatch would generate an error.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-12-11 [07eee5a0d] Create a new type category for "internal use" types.
-->

     <listitem>
      <para>
       Create a new <link
       linkend="catalog-pg-type"><structfield>pg_type.typcategory</structfield></link>
       value for <type>"char"</type> (Tom Lane)
      </para>

      <para>
       Some other internal-use-only values have also been assigned to this column.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-18 [cc333f323] Modify pg_basebackup to use a new COPY subprotocol for b
-->

     <listitem>
      <para>
       Add new protocol message <link
       linkend="protocol-replication-base-backup"><literal>TARGET</literal></link>
       to specify a new <command>COPY</command> method to be for base
       backups (Robert Haas)
      </para>

      <para>
       Modify <link
       linkend="app-pgbasebackup"><application>pg_basebackup</application></link>
       to use this method.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-01-24 [0ad803291] Server-side gzip compression.
Author: Robert Haas <rhaas@postgresql.org>
2022-03-23 [ffd53659c] Replace BASE_BACKUP COMPRESSION_LEVEL option with COMPRE
-->

     <listitem>
      <para>
       Add new protocol message <link
       linkend="protocol-replication-base-backup"><literal>COMPRESSION</literal></link>
       and <literal>COMPRESSION_DETAIL</literal> to specify the compression
       method and options (Robert Haas)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-10 [9cd28c2e5] Remove server support for old BASE_BACKUP command syntax
Author: Robert Haas <rhaas@postgresql.org>
2022-02-10 [0d4513b61] Remove server support for the previous base backup proto
-->

     <listitem>
      <para>
       Remove server support for old <literal>BASE_BACKUP</literal>
       command syntax and base backup protocol (Robert Haas)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-03-15 [e4ba69f3f] Allow extensions to add new backup targets.
-->

     <listitem>
      <para>
       Add support for extensions to set custom backup targets (Robert
       Haas)
      </para>
     </listitem>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2022-04-06 [5c279a6d3] Custom WAL Resource Managers.
-->

     <listitem>
      <para>
       Allow extensions to define their own <acronym>WAL</acronym>
       resource managers (Jeff Davis)
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-01-31 [d10e41d42] Introduce pg_settings_get_flags() to find flags associat
-->

     <listitem>
      <para>
       Add function <link
       linkend="functions-info-catalog-table"><function>pg_settings_get_flags()</function></link>
       to get the flags of server-side variables (Justin Pryzby)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-04-08 [8ec569479] Apply PGDLLIMPORT markings broadly.
-->

     <listitem>
      <para>
       Export all server variables on Windows using
       <literal>PGDLLIMPORT</literal> (Robert Haas)
      </para>

      <para>
       Previously only specific variables where exported.
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-11-05 [db7d1a7b0] pgcrypto: Remove non-OpenSSL support
-->

     <listitem>
      <para>
       Require OpenSSL to build <link
       linkend="pgcrypto"><application>pgcrypto</application></link>
       binaries (Peter Eisentraut)
      </para>
     </listitem>

<!--
Author: Andres Freund <andres@anarazel.de>
2022-02-16 [19252e8ec] plpython: Reject Python 2 during build configuration.
-->

     <listitem>
      <para>
       Disallow building with <application>Python 2</application>
       (Andres Freund)
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-10-07 [92e6a98c3] Adjust configure to insist on Perl version &gt;= 5.8.3.
-->

     <listitem>
      <para>
       Adjust configure to require <application>Perl</application>
       version 5.8.3 or later (Dagfinn Ilmari Mannsåker)
      </para>
     </listitem>

    </itemizedlist>

   </sect3>

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

    <itemizedlist>

<!--
Author: Jeff Davis <jdavis@postgresql.org>
2022-04-08 [2258e76f9] Add contrib/pg_walinspect.
-->

     <listitem>
      <para>
       Add new module <link
       linkend="pgwalinspect"><application>pg_walinspect</application></link>
       (Bharath Rupireddy)
      </para>

      <para>
       This gives <acronym>SQL</acronym>-level output similar to <link
       linkend="pgwaldump"><application>pg_waldump</application></link>.
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-02-03 [5ef1eefd7] Allow archiving via loadable modules.
-->

     <listitem>
      <para>
       Add module <link
       linkend="basic-archive"><application>basic_archive</application></link>
       to perform archiving via a library (Nathan Bossart)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2022-03-15 [c6306db24] Add 'basebackup_to_shell' contrib module.
Author: Robert Haas <rhaas@postgresql.org>
2022-03-30 [26a0c025e] Document basebackup_to_shell.required_role.
-->

     <listitem>
      <para>
       Add module <application><link
       linkend="basebackup-to-shell">basebackup_to_shell</link></application>
       as a custom backup target (Robert Haas) contrib module.
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2022-04-08 [76cbf7edb] pg_stat_statements: Track I/O timing for temporary file
-->

     <listitem>
      <para>
       Add <link
       linkend="pgstatstatements"><application>pg_stat_statements</application></link>
       output for temporary file block I/O (Masahiko Sawada)
      </para>
     </listitem>

<!--
Author: Magnus Hagander <magnus@hagander.net>
2022-04-08 [57d6aea00] Add JIT counters to pg_stat_statements
-->

     <listitem>
      <para>
       Add <acronym>JIT</acronym> counters to pg_stat_statements (Magnus
       Hagander)
      </para>
     </listitem>

<!--
Author: Peter Eisentraut <peter@eisentraut.org>
2021-09-28 [c3b011d99] Support amcheck of sequences
-->

     <listitem>
      <para>
       Allow <link
       linkend="amcheck"><application>amcheck</application></link> to
       check sequences (Mark Dilger)
      </para>
     </listitem>

<!--
Author: Robert Haas <rhaas@postgresql.org>
2021-11-05 [bd807be69] amcheck: Add additional TOAST pointer checks.
-->

     <listitem>
      <para>
       Improve <application>amcheck</application> sanity checks for
       <acronym>TOAST</acronym> tables (Mark Dilger)
      </para>
     </listitem>

<!--
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2021-11-06 [57e3c5160] Add bool GiST opclass to btree_gist
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2021-11-08 [e2fbb8837] Fix gist_bool_ops to use gbtreekey2
Author: Tomas Vondra <tomas.vondra@postgresql.org>
2021-12-11 [4c6145b51] Add bool to btree_gist documentation
-->

     <listitem>
      <para>
       Allow <link
       linkend="btree-gist"><application>btree_gist</application></link>
       indexes on boolean columns (Emre Hasegeli)
      </para>

      <para>
       These can be used for exclusion constraints.
      </para>
     </listitem>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2022-01-12 [134d97463] Include permissive/enforcing state in sepgsql log messag
-->

     <listitem>
      <para>
       Indicate the permissive/enforcing state in <link
       linkend="sepgsql"><application>sepgsql</application></link> log
       messages (Dave Page)
      </para>
     </listitem>

<!--
Author: Michael Paquier <michael@paquier.xyz>
2021-07-12 [127404fbe] pageinspect: Improve page_header() for pages of 32kB
-->

     <listitem>
      <para>
       Fix <link
       linkend="pageinspect"><application>pageinspect</application></link>'s
       <function>page_header()</function> to handle 32 kilobyte page sizes
       (Quan Zongliang)
      </para>

      <para>
       Previously improper negative values could be returned in certain
       cases.
      </para>
     </listitem>

    </itemizedlist>

    <sect4>
     <title><link linkend="postgres-fdw"><application>postgres_fdw</application></link></title>

     <itemizedlist>

<!--
Author: Tom Lane <tgl@sss.pgh.pa.us>
2021-07-30 [5d44fff01] In postgres_fdw, allow CASE expressions to be pushed to
-->

      <listitem>
       <para>
        Allow postgres_fdw to push down <literal>CASE</literal> expressions
        (Alexander Pyhalov)
       </para>
      </listitem>

<!--
Author: Fujii Masao <fujii@postgresql.org>
2021-09-07 [449ab6350] postgres_fdw: Allow application_name of remote connectio
Author: Fujii Masao <fujii@postgresql.org>
2021-12-24 [6e0cb3dec] postgres_fdw: Allow postgres_fdw.application_name to inc
Author: Fujii Masao <fujii@postgresql.org>
2022-02-18 [94c49d534] postgres_fdw: Make postgres_fdw.application_name support
-->

      <listitem>
       <para>
        Add server variable
        <varname>postgres_fdw.application_name</varname> to control the
        application name of postgres_fdw connections (Hayato Kuroda)
       </para>

       <para>
        Previously the remote <link
        linkend="guc-application-name"><varname>application_name</varname></link>
        could only be set on the remote server or via
        <application>postgres_fdw</application> connection specification.
        <varname>postgres_fdw.application_name</varname> also supports
        escape sequences for customization.
       </para>
      </listitem>

<!--
Author: Etsuro Fujita <efujita@postgresql.org>
2022-02-24 [04e706d42] postgres_fdw: Add support for parallel commit.
-->

      <listitem>
       <para>
        Allow parallel commit on <application>postgres_fdw</application>
        servers (Etsuro Fujita)
       </para>

       <para>
        This is enabled with the <literal>CREATE SERVER</literal> option
        <literal>parallel_commit</literal> when using postgres_fdw.
       </para>
      </listitem>

     </itemizedlist>

    </sect4>

   </sect3>

  </sect2>

  <sect2 id="release-15-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>
