From 06beed94067efaf5b93da5041048347fa22a4290 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Fri, 8 Dec 2023 14:04:53 +0100
Subject: [PATCH v1 2/2] Add GUC backtrace_on_internal_error

---
 doc/src/sgml/config.sgml            | 27 +++++++++++++++++++++++++++
 src/backend/utils/error/elog.c      |  8 +++++---
 src/backend/utils/misc/guc_tables.c | 16 ++++++++++++++++
 src/include/utils/guc.h             |  1 +
 4 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 94d1eb2b81..b830539b9a 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -11027,6 +11027,33 @@ <title>Developer Options</title>
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-backtrace-on-internal-error" xreflabel="backtrace_on_internal_error">
+      <term><varname>backtrace_on_internal_error</varname> (<type>boolean</type>)
+      <indexterm>
+        <primary><varname>backtrace_on_internal_error</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        If this parameter is on and an error with error code XX000 (internal
+        error; see also <xref linkend="errcodes-appendix"/>) is raised, then a
+        backtrace is written to the server log together with the error
+        message.  This can be used to debug such internal errors (which should
+        normally not happen in production).  The default is off.
+       </para>
+
+       <para>
+        Backtrace support is not available on all platforms, and the quality
+        of the backtraces depends on compilation options.
+       </para>
+
+       <para>
+        Only superusers and users with the appropriate <literal>SET</literal>
+        privilege can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-debug-discard-caches" xreflabel="debug_discard_caches">
       <term><varname>debug_discard_caches</varname> (<type>integer</type>)
       <indexterm>
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index ecacba4ee1..6a7a487323 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -498,9 +498,11 @@ errfinish(const char *filename, int lineno, const char *funcname)
 
 	/* Collect backtrace, if enabled and we didn't already */
 	if (!edata->backtrace &&
-		edata->funcname &&
-		backtrace_functions &&
-		matches_backtrace_functions(edata->funcname))
+		((edata->funcname &&
+		  backtrace_functions &&
+		  matches_backtrace_functions(edata->funcname)) ||
+		 (edata->sqlerrcode == ERRCODE_INTERNAL_ERROR &&
+		  backtrace_on_internal_error)))
 		set_backtrace(edata, 2);
 
 	/*
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 6474e35ec0..73252d4864 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -527,6 +527,7 @@ double		log_statement_sample_rate = 1.0;
 double		log_xact_sample_rate = 0;
 int			trace_recovery_messages = LOG;
 char	   *backtrace_functions;
+bool		backtrace_on_internal_error = false;
 
 int			temp_file_limit = -1;
 
@@ -810,6 +811,21 @@ StaticAssertDecl(lengthof(config_type_names) == (PGC_ENUM + 1),
 
 struct config_bool ConfigureNamesBool[] =
 {
+	{
+		{"backtrace_on_internal_error", PGC_SUSET, DEVELOPER_OPTIONS,
+			gettext_noop("Log backtrace for any error with error code XX000 (internal error)."),
+			NULL,
+			GUC_NOT_IN_SAMPLE
+		},
+		&backtrace_on_internal_error,
+
+		/*
+		 * TODO: Discussion: Could default to true unconditionally or in
+		 * assert builds?
+		 */
+		false,
+		NULL, NULL, NULL
+	},
 	{
 		{"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
 			gettext_noop("Enables the planner's use of sequential-scan plans."),
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 20fe13702b..b4df0b6678 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -264,6 +264,7 @@ extern PGDLLIMPORT int log_temp_files;
 extern PGDLLIMPORT double log_statement_sample_rate;
 extern PGDLLIMPORT double log_xact_sample_rate;
 extern PGDLLIMPORT char *backtrace_functions;
+extern PGDLLIMPORT bool backtrace_on_internal_error;
 
 extern PGDLLIMPORT int temp_file_limit;
 
-- 
2.43.0