doc: Add note about postgres_fdw.application_name.

MasaoFujii · MasaoFujii · commit 58e2e6eb67fe · 2021-12-16T15:18:30.000+09:00
postgres_fdw.application_name can be any string of any length and contain even non-ASCII characters. However when it's passed to and used as application_name in a foreign server, it's truncated to less than NAMEDATALEN characters and any characters other than printable ASCII ones in it will be replaced with question marks. This commit adds these notes into the docs. Author: Hayato Kuroda Reviewed-by: Kyotaro Horiguchi, Fujii Masao Discussion: https://postgr.es/m/TYCPR01MB5870D1E8B949DAF6D3B84E02F5F29@TYCPR01MB5870.jpnprd01.prod.outlook.com
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml
@@ -936,6 +936,16 @@ postgres=# SELECT postgres_fdw_disconnect_all();
       Note that change of this parameter doesn't affect any existing
       connections until they are re-established.
      </para>
+     <para>
+      <varname>postgres_fdw.application_name</varname> can be any string
+      of any length and contain even non-ASCII characters.  However when
+      it's passed to and used as <varname>application_name</varname>
+      in a foreign server, note that it will be truncated to less than
+      <symbol>NAMEDATALEN</symbol> characters and any characters other
+      than printable ASCII ones in it will be replaced with question
+      marks (<literal>?</literal>).
+      See <xref linkend="guc-application-name"/> for details.
+     </para>
     </listitem>
    </varlistentry>
   </variablelist>
