From db01f797dd48f826c62e1b8eea70f11fe7ff3efc Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Tue, 20 Apr 2021 12:57:59 -0400
Subject: Fix interaction of log_line_prefix's query_id and log_statement

log_statement is issued before query_id can be computed, so properly
clear the value, and document the interaction.

Reported-by: Fujii Masao, Michael Paquier

Discussion: https://postgr.es/m/YHPkU8hFi4no4NSw@paquier.xyz

Author: Julien Rouhaud
---
 doc/src/sgml/config.sgml | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'doc/src')

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 776ab1a8c8b..dd7ebe7a9da 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7139,6 +7139,16 @@ log_line_prefix = '%m [%p] %q%u@%d/%a '
 </programlisting>
         </para>
        </tip>
+
+       <note>
+        <para>
+         The <literal>%Q</literal> escape always reports a zero identifier
+         for lines output by <xref linkend="guc-log-statement"/> because
+         <varname>log_statement</varname> generates output before an
+         identifier can be calculated, including invalid statements for
+         which an identifier cannot be calculated.
+        </para>
+       </note>
       </listitem>
      </varlistentry>
 
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