From 8e756854de95794f3d30584cee70b94b5822e424 Mon Sep 17 00:00:00 2001
From: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Date: Wed, 27 Sep 2023 12:12:16 +0000
Subject: [PATCH v31] Fix description for handling of non-printable ASCII
 characters
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45b1a67a changed the behavior when characters that are not printable ASCII were
used for three configuration parameters (application_name, cluster_name, and
postgres_fdw.application_name), but it was not documented. This commit fixes
that.

PG15 and prior:

```
postgres=# SET application_name TO 'あああ';
SET
postgres=# SHOW application_name ;
 application_name
------------------
 ?????????
(1 row)
```

PG16 and later:

```
postgres=# SET application_name TO 'あああ';
SET
postgres=# SHOW application_name ;
           application_name
--------------------------------------
 \xe3\x81\x82\xe3\x81\x82\xe3\x81\x82
(1 row)
```
---
 doc/src/sgml/config.sgml       | 22 ++++++++++++++--------
 doc/src/sgml/postgres-fdw.sgml | 12 +++++++-----
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 38684af5b1..9163e55c6d 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -6892,9 +6892,11 @@ local0.*    /var/log/postgresql
         The name will be displayed in the <structname>pg_stat_activity</structname> view
         and included in CSV log entries.  It can also be included in regular
         log entries via the <xref linkend="guc-log-line-prefix"/> parameter.
-        Only printable ASCII characters may be used in the
-        <varname>application_name</varname> value. Other characters will be
-        replaced with question marks (<literal>?</literal>).
+        The bytes of the string which are not printable ASCII, like
+        <literal>\x03</literal>, are replaced with the
+        <productname>PostgreSQL</productname> <link
+        linkend="sql-syntax-strings-escape">C-style escaped hexadecimal byte
+        value</link>.
        </para>
       </listitem>
      </varlistentry>
@@ -7889,11 +7891,15 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
        <para>
         The name can be any string of less
         than <symbol>NAMEDATALEN</symbol> characters (64 characters in a standard
-        build). Only printable ASCII characters may be used in the
-        <varname>cluster_name</varname> value. Other characters will be
-        replaced with question marks (<literal>?</literal>).  No name is shown
-        if this parameter is set to the empty string <literal>''</literal> (which is
-        the default). This parameter can only be set at server start.
+        build).
+        The bytes of the string which are not printable ASCII, like
+        <literal>\x03</literal>, are replaced with the
+        <productname>PostgreSQL</productname> <link
+        linkend="sql-syntax-strings-escape">C-style escaped hexadecimal byte
+        value</link>.
+        No name is shown if this parameter is set to the empty string
+        <literal>''</literal> (which is the default). This parameter can only
+        be set at server start.
        </para>
       </listitem>
      </varlistentry>
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml
index 5062d712e7..dcbcf84911 100644
--- a/doc/src/sgml/postgres-fdw.sgml
+++ b/doc/src/sgml/postgres-fdw.sgml
@@ -1064,12 +1064,14 @@ postgres=# SELECT postgres_fdw_disconnect_all();
      </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>
+      of any length and contain even characters that are not printable ASCII.
+      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 anything other than
-      printable ASCII characters will be replaced with question
-      marks (<literal>?</literal>).
+      <symbol>NAMEDATALEN</symbol> characters and the bytes of the string that
+      are not printable ASCII characters are replaced with the
+      <productname>PostgreSQL</productname> <link
+      linkend="sql-syntax-strings-escape">C-style escaped hexadecimal byte
+      value</link>.
       See <xref linkend="guc-application-name"/> for details.
      </para>
 
-- 
2.27.0