Make recovery_target_time reloadable without server restart

doc/src/sgml/config.sgml

@@ -4253,7 +4253,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
       <varname>recovery_target_time</varname>, or <varname>recovery_target_xid</varname>
       can be used; if more than one of these is specified in the configuration
       file, an error will be raised.
-      These parameters can only be set at server start.
+      These parameters can be changed by reloading the server configuration
+      without requiring a restart, except for
+      <varname>recovery_target_timeline</varname> which can only be set at
+      server start.
      </para>
 
      <variablelist>
@@ -4274,6 +4277,9 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         Technically, this is a string parameter, but <literal>'immediate'</literal>
         is currently the only allowed value.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4288,6 +4294,9 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         This parameter specifies the named restore point (created with
         <function>pg_create_restore_point()</function>) to which recovery will proceed.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4314,6 +4323,29 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         numeric offset from UTC, or you can write a full time zone name,
         e.g., <literal>Europe/Helsinki</literal> not <literal>EEST</literal>.
        </para>
+
+       <para>
+        This parameter can be changed by reloading the server configuration
+        (for example, via <function>pg_reload_conf()</function>) without
+        requiring a server restart.
+       </para>
+
+       <para>
+        The value is re-parsed under the current
+        <xref linkend="guc-timezone"/> setting on each reload.  To avoid
+        ambiguity, use an explicit time zone offset, e.g.,
+        <literal>'2024-01-15 10:30:00+00'</literal>, to ensure deterministic
+        behavior regardless of the server's timezone configuration.
+       </para>
+
+       <para>
+        When <xref linkend="guc-recovery-target-action"/> is set to
+        <literal>pause</literal> and recovery is paused at the target,
+        changing <varname>recovery_target_time</varname> to a later value
+        and reloading the configuration will automatically resume WAL replay
+        toward the new target.  Setting it to an equal or earlier value while
+        paused is a no-op.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4349,6 +4381,9 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         The effective transaction ID (the 32-bit portion) must be greater than
         or equal to 3.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4366,6 +4401,13 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         parameter is parsed using the system data type
         <link linkend="datatype-pg-lsn"><type>pg_lsn</type></link>.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+        When <xref linkend="guc-recovery-target-action"/> is set to
+        <literal>pause</literal> and recovery is paused at the target,
+        advancing the LSN to a later value and reloading the configuration
+        will automatically resume WAL replay toward the new target.
+       </para>
       </listitem>
      </varlistentry>
      </variablelist>
@@ -4395,6 +4437,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         having exactly the target WAL location (LSN), commit time, or transaction ID, respectively, will
         be included in the recovery.  Default is <literal>on</literal>.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+        The new value takes effect on the next recovery stop evaluation.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4430,6 +4476,9 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         a state that itself was reached after a point-in-time recovery.
         See <xref linkend="backup-timelines"/> for discussion.
        </para>
+       <para>
+        This parameter can only be set at server start.
+       </para>
       </listitem>
      </varlistentry>
 
@@ -4457,9 +4506,8 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         using <function>pg_wal_replay_resume()</function> (see
         <xref linkend="functions-recovery-control-table"/>), which then
         causes recovery to end. If this recovery target is not the
-        desired stopping point, then shut down the server, change the
-        recovery target settings to a later target and restart to
-        continue recovery.
+        desired stopping point, change the recovery target settings to a
+        later target and reload the configuration to continue recovery.
        </para>
        <para>
         The <literal>shutdown</literal> setting is useful to have the instance ready
@@ -4482,6 +4530,12 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         a setting of <literal>pause</literal> will act the same as
         <literal>promote</literal>.
        </para>
+       <para>
+        This parameter can be changed by reloading the server configuration.
+        For example, changing from <literal>pause</literal> to
+        <literal>promote</literal> while recovery is paused at the target
+        will trigger promotion.
+       </para>
        <para>
         In any case, if a recovery target is configured but the archive
         recovery ends before the target is reached, the server will shut down