GUC flags

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 25ac4ca85b..927212b8ae 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2131,8 +2131,8 @@ static struct config_int ConfigureNamesInt[] =
 {
 	{
 		{"archive_timeout", PGC_SIGHUP, WAL_ARCHIVING,
-			gettext_noop("Forces a switch to the next WAL file if a "
-						 "new file has not been started within N seconds."),
+			gettext_noop("Sets the amount of time to wait before forcing a "
+						 "switch to the next WAL file."),
 			NULL,
 			GUC_UNIT_S
 		},
@@ -2142,7 +2142,8 @@ static struct config_int ConfigureNamesInt[] =
 	},
 	{
 		{"post_auth_delay", PGC_BACKEND, DEVELOPER_OPTIONS,
-			gettext_noop("Waits N seconds on connection startup after authentication."),
+			gettext_noop("Sets the amount of seconds to wait on connection "
+						 "startup after authentication."),
 			gettext_noop("This allows attaching a debugger to the process."),
 			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
 		},
@@ -2762,7 +2763,8 @@ static struct config_int ConfigureNamesInt[] =
 	{
 		/* Not for general use */
 		{"pre_auth_delay", PGC_SIGHUP, DEVELOPER_OPTIONS,
-			gettext_noop("Waits N seconds on connection startup before authentication."),
+			gettext_noop("Sets the amount of seconds to wait on connection "
+						 "startup before authentication."),
 			gettext_noop("This allows attaching a debugger to the process."),
 			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
 		},
@@ -2819,10 +2821,10 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"checkpoint_warning", PGC_SIGHUP, WAL_CHECKPOINTS,
-			gettext_noop("Enables warnings if checkpoint segments are filled more "
-						 "frequently than this."),
+			gettext_noop("Sets the maximum time before warning if checkpoints "
+						 "triggered by WAL volume happen too frequently."),
 			gettext_noop("Write a message to the server log if checkpoints "
-						 "caused by the filling of checkpoint segment files happens more "
+						 "caused by the filling of WAL segment files happens more "
 						 "frequently than this number of seconds. Zero turns off the warning."),
 			GUC_UNIT_S
 		},
@@ -3006,7 +3008,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_parameter_max_length", PGC_SUSET, LOGGING_WHAT,
-			gettext_noop("When logging statements, limit logged parameter values to first N bytes."),
+			gettext_noop("Sets the maximum amount of data logged for bind "
+						 "parameter values when logging statements."),
 			gettext_noop("-1 to print values in full."),
 			GUC_UNIT_BYTE
 		},
@@ -3017,7 +3020,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_parameter_max_length_on_error", PGC_USERSET, LOGGING_WHAT,
-			gettext_noop("When reporting an error, limit logged parameter values to first N bytes."),
+			gettext_noop("Sets the maximum amount of data logged for bind "
+						 "parameter values when logging statements, on error."),
 			gettext_noop("-1 to print values in full."),
 			GUC_UNIT_BYTE
 		},
@@ -3143,7 +3147,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
-			gettext_noop("Automatic log file rotation will occur after N minutes."),
+			gettext_noop("Sets the maximum amount of time to wait before "
+						 "forcing log file rotation."),
 			NULL,
 			GUC_UNIT_MIN
 		},
@@ -3154,7 +3159,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_rotation_size", PGC_SIGHUP, LOGGING_WHERE,
-			gettext_noop("Automatic log file rotation will occur after N kilobytes."),
+			gettext_noop("Sets the maximum size of log file to reach before "
+						 "forcing log file rotation."),
 			NULL,
 			GUC_UNIT_KB
 		},

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 25ac4ca85b..003d649ff5 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2131,8 +2131,8 @@ static struct config_int ConfigureNamesInt[] =
 {
 	{
 		{"archive_timeout", PGC_SIGHUP, WAL_ARCHIVING,
-			gettext_noop("Forces a switch to the next WAL file if a "
-						 "new file has not been started within N seconds."),
+			gettext_noop("Sets the amount of time to wait before forcing a "
+						 "switch to the next WAL file."),
 			NULL,
 			GUC_UNIT_S
 		},
@@ -2142,7 +2142,8 @@ static struct config_int ConfigureNamesInt[] =
 	},
 	{
 		{"post_auth_delay", PGC_BACKEND, DEVELOPER_OPTIONS,
-			gettext_noop("Waits N seconds on connection startup after authentication."),
+			gettext_noop("Sets the amount of time to wait on connection "
+						 "startup after authentication."),
 			gettext_noop("This allows attaching a debugger to the process."),
 			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
 		},
@@ -2762,7 +2763,8 @@ static struct config_int ConfigureNamesInt[] =
 	{
 		/* Not for general use */
 		{"pre_auth_delay", PGC_SIGHUP, DEVELOPER_OPTIONS,
-			gettext_noop("Waits N seconds on connection startup before authentication."),
+			gettext_noop("Sets the amount of time to wait on connection "
+						 "startup before authentication."),
 			gettext_noop("This allows attaching a debugger to the process."),
 			GUC_NOT_IN_SAMPLE | GUC_UNIT_S
 		},
@@ -2819,10 +2821,10 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"checkpoint_warning", PGC_SIGHUP, WAL_CHECKPOINTS,
-			gettext_noop("Enables warnings if checkpoint segments are filled more "
-						 "frequently than this."),
+			gettext_noop("Sets the maximum time before warning if checkpoints "
+						 "triggered by WAL volume happen too frequently."),
 			gettext_noop("Write a message to the server log if checkpoints "
-						 "caused by the filling of checkpoint segment files happens more "
+						 "caused by the filling of WAL segment files happen more "
 						 "frequently than this number of seconds. Zero turns off the warning."),
 			GUC_UNIT_S
 		},
@@ -3006,7 +3008,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_parameter_max_length", PGC_SUSET, LOGGING_WHAT,
-			gettext_noop("When logging statements, limit logged parameter values to first N bytes."),
+			gettext_noop("Sets the maximum length in bytes of data logged for bind "
+						 "parameter values when logging statements."),
 			gettext_noop("-1 to print values in full."),
 			GUC_UNIT_BYTE
 		},
@@ -3017,7 +3020,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_parameter_max_length_on_error", PGC_USERSET, LOGGING_WHAT,
-			gettext_noop("When reporting an error, limit logged parameter values to first N bytes."),
+			gettext_noop("Sets the maximum length in bytes of data logged for bind "
+						 "parameter values when logging statements, on error."),
 			gettext_noop("-1 to print values in full."),
 			GUC_UNIT_BYTE
 		},
@@ -3143,7 +3147,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
-			gettext_noop("Automatic log file rotation will occur after N minutes."),
+			gettext_noop("Sets the amount of time to wait before forcing "
+						 "log file rotation."),
 			NULL,
 			GUC_UNIT_MIN
 		},
@@ -3154,7 +3159,8 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"log_rotation_size", PGC_SIGHUP, LOGGING_WHERE,
-			gettext_noop("Automatic log file rotation will occur after N kilobytes."),
+			gettext_noop("Sets the maximum size of log file to reach before "
+						 "forcing log file rotation."),
 			NULL,
 			GUC_UNIT_KB
 		},

From 8d9130a25a59630063e644a884d354eb085faa4e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4f..323ca13191 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.0

From 2cd8cdbe9f79d88cc920a6e093fa61780ea07a44 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH 1/2] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4f..323ca13191 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.0

From 838656dc9e88a51940a643f2d20970de8b5bfc9a Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH 2/2] Expose GUC flags in pg_settings; retire ./check_guc

---
 src/backend/utils/misc/check_guc    |  29 -------
 src/backend/utils/misc/guc.c        |   8 +-
 src/include/catalog/pg_proc.dat     |   6 +-
 src/test/regress/expected/guc.out   | 115 ++++++++++++++++++++++++++++
 src/test/regress/expected/rules.out |   5 +-
 src/test/regress/sql/guc.sql        |  63 +++++++++++++++
 6 files changed, 191 insertions(+), 35 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191..0000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ee6a838b3a..fdadeda470 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9889,6 +9889,10 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
+
+	/* flags */
+	snprintf(buffer, sizeof(buffer), "%d", conf->flags);
+	values[17] = pstrdup(buffer);
 }
 
 /*
@@ -9944,7 +9948,7 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	17
+#define NUM_PG_SETTINGS_ATTS	18
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -10006,6 +10010,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
+						   INT4OID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 79d787cd26..c2d3f35862 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6110,9 +6110,9 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,int4}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
   prosrc => 'show_all_settings' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 2433038c3e..f99049cd55 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -832,3 +832,118 @@ ERROR:  unrecognized configuration parameter "foo"
 RESET plpgsql.extra_foo_warnings;
 WARNING:  unrecognized configuration parameter "plpgsql.extra_foo_warnings"
 DETAIL:  "plpgsql" is a reserved prefix.
+--
+-- Test GUC categories and flags.
+--
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE (flags&32)=0 EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE (flags&32)=0
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | not_in_sample 
+------+----------+---------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | not_in_sample 
+------------------------+-------------------------------------------------+---------------
+ application_name       | Reporting and Logging / What to Log             | t
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | t
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | t
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | t
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE category~'^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | guc_explain 
+---------------------------+--------------------------------------+-------------
+ default_statistics_target | Query Tuning / Other Planner Options | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE guc_explain AND NOT category~'^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | guc_explain 
+---------------------+-------------------------------------------------+-------------
+ explain_regress     | Developer Options                               | t
+ force_parallel_mode | Developer Options                               | t
+ search_path         | Client Connection Defaults / Statement Behavior | t
+(3 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM (SELECT name, category, (flags&2097152) != 0 AS guc_computed FROM pg_settings)x
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | guc_computed 
+------+----------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | not_in_sample 
+------+----------+---------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all 
+------+----------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all 
+------------------------+-------------------------------------------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | not_in_sample 
+------+----------+-------------+---------------
+(0 rows)
+
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index b58b062b10..2db00f2a8d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1724,8 +1724,9 @@ pg_settings| SELECT a.name,
     a.reset_val,
     a.sourcefile,
     a.sourceline,
-    a.pending_restart
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
+    a.pending_restart,
+    a.flags
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index b57758ed27..0da67b9582 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -322,3 +322,66 @@ SHOW plpgsql.extra_foo_warnings;  -- but the parameter is set
 -- cleanup
 RESET foo;
 RESET plpgsql.extra_foo_warnings;
+
+--
+-- Test GUC categories and flags.
+--
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE (flags&32)=0 EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE (flags&32)=0
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE category~'^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE guc_explain AND NOT category~'^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM (SELECT name, category, (flags&2097152) != 0 AS guc_computed FROM pg_settings)x
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
-- 
2.17.0

From f18854a561d779c3d77689f9778dc175db1a2349 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH v2 1/2] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4f..323ca13191 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.0

From ffaffb0350678c7c774aad0b05a7b49f301c08e6 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH v2 2/2] Expose GUC flags in pg_settings; retire ./check_guc

---
 src/backend/utils/misc/check_guc    |  29 -------
 src/backend/utils/misc/guc.c        |   8 +-
 src/include/catalog/pg_proc.dat     |   6 +-
 src/test/regress/expected/guc.out   | 114 ++++++++++++++++++++++++++++
 src/test/regress/expected/rules.out |   5 +-
 src/test/regress/sql/guc.sql        |  63 +++++++++++++++
 6 files changed, 190 insertions(+), 35 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191..0000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f736e8d872..7d4e2e0374 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9889,6 +9889,10 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
+
+	/* flags */
+	snprintf(buffer, sizeof(buffer), "%d", conf->flags);
+	values[17] = pstrdup(buffer);
 }
 
 /*
@@ -9944,7 +9948,7 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	17
+#define NUM_PG_SETTINGS_ATTS	18
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -10006,6 +10010,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
+						   INT4OID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 4d992dc224..ee86d86905 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6092,9 +6092,9 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,int4}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
   prosrc => 'show_all_settings' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 2433038c3e..681cf742d1 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -832,3 +832,117 @@ ERROR:  unrecognized configuration parameter "foo"
 RESET plpgsql.extra_foo_warnings;
 WARNING:  unrecognized configuration parameter "plpgsql.extra_foo_warnings"
 DETAIL:  "plpgsql" is a reserved prefix.
+--
+-- Test GUC categories and flags.
+--
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE (flags&32)=0 EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE (flags&32)=0
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | not_in_sample 
+------+----------+---------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | not_in_sample 
+------------------------+-------------------------------------------------+---------------
+ application_name       | Reporting and Logging / What to Log             | t
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | t
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | t
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | t
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE category~'^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | guc_explain 
+---------------------------+--------------------------------------+-------------
+ default_statistics_target | Query Tuning / Other Planner Options | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE guc_explain AND NOT category~'^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | guc_explain 
+---------------------+-------------------------------------------------+-------------
+ force_parallel_mode | Developer Options                               | t
+ search_path         | Client Connection Defaults / Statement Behavior | t
+(2 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM (SELECT name, category, (flags&2097152) != 0 AS guc_computed FROM pg_settings)x
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | guc_computed 
+------+----------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | not_in_sample 
+------+----------+---------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all 
+------+----------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all 
+------------------------+-------------------------------------------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | not_in_sample 
+------+----------+-------------+---------------
+(0 rows)
+
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index b58b062b10..2db00f2a8d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1724,8 +1724,9 @@ pg_settings| SELECT a.name,
     a.reset_val,
     a.sourcefile,
     a.sourceline,
-    a.pending_restart
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
+    a.pending_restart,
+    a.flags
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index b57758ed27..0da67b9582 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -322,3 +322,66 @@ SHOW plpgsql.extra_foo_warnings;  -- but the parameter is set
 -- cleanup
 RESET foo;
 RESET plpgsql.extra_foo_warnings;
+
+--
+-- Test GUC categories and flags.
+--
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE (flags&32)=0 EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln~'^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE (flags&32)=0
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE category~'^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM (SELECT name, category, (flags&1048576) != 0 AS guc_explain FROM pg_settings)x
+WHERE guc_explain AND NOT category~'^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM (SELECT name, category, (flags&2097152) != 0 AS guc_computed FROM pg_settings)x
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM (SELECT name, category, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&8)!=0 AS no_reset_all FROM pg_settings)x
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM (SELECT name, category, (flags&4)!=0 AS no_show_all, (flags&32) != 0 AS not_in_sample FROM pg_settings)x
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
-- 
2.17.0

From 7f620514e85d19e5fb3b108c4de3f6f41f295114 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH v3 1/3] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4ff..323ca13191b 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.1

From e567e0ea90adde3f13f0bfcd5cf769ca71f60e78 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH v3 2/3] Expose GUC flags in pg_settings; retire ./check_guc

---
 src/backend/utils/misc/check_guc    |  29 -------
 src/backend/utils/misc/guc.c        |   8 +-
 src/include/catalog/pg_proc.dat     |   6 +-
 src/test/regress/expected/guc.out   | 124 ++++++++++++++++++++++++++++
 src/test/regress/expected/rules.out |   5 +-
 src/test/regress/sql/guc.sql        |  74 +++++++++++++++++
 6 files changed, 211 insertions(+), 35 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191b..00000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f9504d3aec4..822dfed2b6c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9849,6 +9849,10 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
+
+	/* flags */
+	snprintf(buffer, sizeof(buffer), "%d", conf->flags);
+	values[17] = pstrdup(buffer);
 }
 
 /*
@@ -9904,7 +9908,7 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	17
+#define NUM_PG_SETTINGS_ATTS	18
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -9966,6 +9970,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
+						   INT4OID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 4d992dc2241..ee86d869057 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6092,9 +6092,9 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,int4}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
   prosrc => 'show_all_settings' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 59da91ff04d..d0f3cda22c8 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -813,3 +813,127 @@ set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
 ERROR:  tables declared WITH OIDS are not supported
+--
+-- Test GUC categories and flags.
+--
+begin;
+CREATE TEMP TABLE pg_settings AS SELECT name, category,
+	(flags&4) != 0 AS no_show_all,
+	(flags&8) != 0 AS no_reset_all,
+	(flags&32) != 0 AS not_in_sample,
+	(flags&1048576) != 0 AS guc_explain,
+	(flags&2097152) != 0 AS guc_computed
+	FROM pg_settings;
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ application_name       | Reporting and Logging / What to Log             | f           | f            | t             | f           | f
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------------+--------------------------------------+-------------+--------------+---------------+-------------+--------------
+ default_statistics_target | Query Tuning / Other Planner Options | f           | f            | f             | f           | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ force_parallel_mode | Developer Options                               | f           | f            | t             | t           | f
+ search_path         | Client Connection Defaults / Statement Behavior | f           | f            | f             | t           | f
+(2 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM pg_settings
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+DROP TABLE pg_settings;
+rollback;
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index b58b062b10d..2db00f2a8df 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1724,8 +1724,9 @@ pg_settings| SELECT a.name,
     a.reset_val,
     a.sourcefile,
     a.sourceline,
-    a.pending_restart
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
+    a.pending_restart,
+    a.flags
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index c39c11388d5..66eb28823b3 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -311,3 +311,77 @@ reset check_function_bodies;
 set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
+
+--
+-- Test GUC categories and flags.
+--
+begin;
+CREATE TEMP TABLE pg_settings AS SELECT name, category,
+	(flags&4) != 0 AS no_show_all,
+	(flags&8) != 0 AS no_reset_all,
+	(flags&32) != 0 AS not_in_sample,
+	(flags&1048576) != 0 AS guc_explain,
+	(flags&2097152) != 0 AS guc_computed
+	FROM pg_settings;
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM pg_settings
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+
+DROP TABLE pg_settings;
+rollback;
-- 
2.17.1

From 1d5d95c9146f75f012f0b3df133f0e82859c0bde Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 26 Dec 2021 20:12:16 -0600
Subject: [PATCH v3 3/3] f!pg_get_guc_flags

---
 src/backend/utils/misc/guc.c        | 26 +++++++++++++++++++-------
 src/include/catalog/pg_proc.dat     | 10 +++++++---
 src/test/regress/expected/guc.out   |  2 +-
 src/test/regress/expected/rules.out |  5 ++---
 src/test/regress/sql/guc.sql        |  2 +-
 5 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 822dfed2b6c..91ff2a18875 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9849,10 +9849,6 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
-
-	/* flags */
-	snprintf(buffer, sizeof(buffer), "%d", conf->flags);
-	values[17] = pstrdup(buffer);
 }
 
 /*
@@ -9904,11 +9900,29 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text(varval));
 }
 
+/*
+ * Return the flags for the specified GUC, or NULL if it doesn't exist.
+ */
+Datum
+pg_get_guc_flags(PG_FUNCTION_ARGS)
+{
+	char *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
+	struct config_generic *record;
+
+	record = find_option(varname, false, true, ERROR);
+
+	/* return NULL if no such variable */
+	if (record == NULL)
+		PG_RETURN_NULL();
+
+	PG_RETURN_INT32(record->flags);
+}
+
 /*
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	18
+#define NUM_PG_SETTINGS_ATTS	17
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -9970,8 +9984,6 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
-						   INT4OID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index ee86d869057..7fa701fe815 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6092,10 +6092,14 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,int4}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
   prosrc => 'show_all_settings' },
+{ oid => '6116', descr => 'return flags for specified GUC',
+  proname => 'pg_get_guc_flags', provolatile => 's',
+  prorettype => 'int4', proargtypes => 'text',
+  prosrc => 'pg_get_guc_flags' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index d0f3cda22c8..f7dd6c0b299 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -823,7 +823,7 @@ CREATE TEMP TABLE pg_settings AS SELECT name, category,
 	(flags&32) != 0 AS not_in_sample,
 	(flags&1048576) != 0 AS guc_explain,
 	(flags&2097152) != 0 AS guc_computed
-	FROM pg_settings;
+	FROM pg_settings, pg_get_guc_flags(name) AS flags;
 -- test that GUCS are in postgresql.conf
 SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample EXCEPT
 SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2db00f2a8df..b58b062b10d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1724,9 +1724,8 @@ pg_settings| SELECT a.name,
     a.reset_val,
     a.sourcefile,
     a.sourceline,
-    a.pending_restart,
-    a.flags
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
+    a.pending_restart
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index 66eb28823b3..81eac9b8ed2 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -322,7 +322,7 @@ CREATE TEMP TABLE pg_settings AS SELECT name, category,
 	(flags&32) != 0 AS not_in_sample,
 	(flags&1048576) != 0 AS guc_explain,
 	(flags&2097152) != 0 AS guc_computed
-	FROM pg_settings;
+	FROM pg_settings, pg_get_guc_flags(name) AS flags;
 
 -- test that GUCS are in postgresql.conf
 SELECT lower(name) FROM pg_settings WHERE NOT not_in_sample EXCEPT
-- 
2.17.1

From 713046d82668c4e189b78e9e274b272bccaaa480 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH v4 1/2] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4ff..323ca13191b 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.1

From d4773ee874ddc6aaa1238e4d1ae7ec6f8e20f36e Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH v4 2/2] Expose GUC flags in SQL function; retire ./check_guc

---
 src/backend/catalog/system_views.sql |  19 ++++-
 src/backend/utils/misc/check_guc     |  29 -------
 src/backend/utils/misc/guc.c         |  37 +++++++-
 src/include/catalog/pg_proc.dat      |   6 +-
 src/test/regress/expected/guc.out    | 122 +++++++++++++++++++++++++++
 src/test/regress/expected/rules.out  |   2 +-
 src/test/regress/sql/guc.sql         |  72 ++++++++++++++++
 7 files changed, 252 insertions(+), 35 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 61b515cdb85..e2c01443cb6 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -580,7 +580,24 @@ FROM
     JOIN pg_authid rol ON l.classoid = rol.tableoid AND l.objoid = rol.oid;
 
 CREATE VIEW pg_settings AS
-    SELECT * FROM pg_show_all_settings() AS A;
+    SELECT a.name,
+    a.setting,
+    a.unit,
+    a.category,
+    a.short_desc,
+    a.extra_desc,
+    a.context,
+    a.vartype,
+    a.source,
+    a.min_val,
+    a.max_val,
+    a.enumvals,
+    a.boot_val,
+    a.reset_val,
+    a.sourcefile,
+    a.sourceline,
+    a.pending_restart
+    FROM pg_show_all_settings() AS A;
 
 CREATE RULE pg_settings_u AS
     ON UPDATE TO pg_settings
diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191b..00000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index f9504d3aec4..9b6ea9279bd 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9622,6 +9622,36 @@ GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
 	return _ShowOption(record, true);
 }
 
+/*
+ * Return an text[] array of the given flags (or a useful subset?) XXX
+ */
+static char *
+get_flags_array_text(int flags)
+{
+	StringInfoData ret;
+
+	initStringInfo(&ret);
+	appendStringInfoChar(&ret, '{');
+
+	if (flags & GUC_NO_SHOW_ALL)
+		appendStringInfo(&ret, "NO_SHOW_ALL,");
+	if (flags & GUC_NO_RESET_ALL)
+		appendStringInfo(&ret, "NO_RESET_ALL,");
+	if (flags & GUC_NOT_IN_SAMPLE)
+		appendStringInfo(&ret, "NOT_IN_SAMPLE,");
+	if (flags & GUC_EXPLAIN)
+		appendStringInfo(&ret, "EXPLAIN,");
+	if (flags & GUC_RUNTIME_COMPUTED)
+		appendStringInfo(&ret, "RUNTIME_COMPUTED,");
+
+	/* Remove trailing comma, if any */
+	if (ret.len > 1)
+		ret.data[--ret.len] = '\0';
+
+	appendStringInfoChar(&ret, '}');
+	return ret.data;
+}
+
 /*
  * Return GUC variable value by variable number; optionally return canonical
  * form of name.  Return value is palloc'd.
@@ -9849,6 +9879,9 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
+
+	/* flags */
+	values[17] = get_flags_array_text(conf->flags);
 }
 
 /*
@@ -9904,7 +9937,7 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	17
+#define NUM_PG_SETTINGS_ATTS	18
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -9966,6 +9999,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
+						   TEXTARRAYOID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 4d992dc2241..7e7e9a48fac 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6092,9 +6092,9 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,_text}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
   prosrc => 'show_all_settings' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 59da91ff04d..d27b7c24747 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -813,3 +813,125 @@ set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
 ERROR:  tables declared WITH OIDS are not supported
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings();
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ application_name       | Reporting and Logging / What to Log             | f           | f            | t             | f           | f
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------------+--------------------------------------+-------------+--------------+---------------+-------------+--------------
+ default_statistics_target | Query Tuning / Other Planner Options | f           | f            | f             | f           | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ force_parallel_mode | Developer Options                               | f           | f            | t             | t           | f
+ search_path         | Client Connection Defaults / Statement Behavior | f           | f            | f             | t           | f
+(2 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+DROP TABLE pg_settings_flags;
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index b58b062b10d..71cbdc37233 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1725,7 +1725,7 @@ pg_settings| SELECT a.name,
     a.sourcefile,
     a.sourceline,
     a.pending_restart
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index c39c11388d5..72b4c367941 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -311,3 +311,75 @@ reset check_function_bodies;
 set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
+
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings();
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) = .*', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+
+DROP TABLE pg_settings_flags;
-- 
2.17.1

From f475b7eced95bb792c4509aa87373348b375742a Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH 2/2] Expose GUC flags in SQL function; retire ./check_guc

---
 src/backend/catalog/system_views.sql |  19 ++++-
 src/backend/utils/misc/check_guc     |  29 -------
 src/backend/utils/misc/guc.c         |  37 +++++++-
 src/include/catalog/pg_proc.dat      |   6 +-
 src/test/regress/expected/guc.out    | 122 +++++++++++++++++++++++++++
 src/test/regress/expected/rules.out  |   2 +-
 src/test/regress/sql/guc.sql         |  72 ++++++++++++++++
 7 files changed, 252 insertions(+), 35 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 3cb69b1f87b..cdae0616bdd 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -582,7 +582,24 @@ FROM
     JOIN pg_authid rol ON l.classoid = rol.tableoid AND l.objoid = rol.oid;
 
 CREATE VIEW pg_settings AS
-    SELECT * FROM pg_show_all_settings() AS A;
+    SELECT a.name,
+    a.setting,
+    a.unit,
+    a.category,
+    a.short_desc,
+    a.extra_desc,
+    a.context,
+    a.vartype,
+    a.source,
+    a.min_val,
+    a.max_val,
+    a.enumvals,
+    a.boot_val,
+    a.reset_val,
+    a.sourcefile,
+    a.sourceline,
+    a.pending_restart
+    FROM pg_show_all_settings() AS A;
 
 CREATE RULE pg_settings_u AS
     ON UPDATE TO pg_settings
diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191b..00000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 4c94f09c645..2cb84d68610 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9634,6 +9634,36 @@ GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
 	return _ShowOption(record, true);
 }
 
+/*
+ * Return an text[] array of the given flags (or a useful subset?) XXX
+ */
+static char *
+get_flags_array_text(int flags)
+{
+	StringInfoData ret;
+
+	initStringInfo(&ret);
+	appendStringInfoChar(&ret, '{');
+
+	if (flags & GUC_NO_SHOW_ALL)
+		appendStringInfo(&ret, "NO_SHOW_ALL,");
+	if (flags & GUC_NO_RESET_ALL)
+		appendStringInfo(&ret, "NO_RESET_ALL,");
+	if (flags & GUC_NOT_IN_SAMPLE)
+		appendStringInfo(&ret, "NOT_IN_SAMPLE,");
+	if (flags & GUC_EXPLAIN)
+		appendStringInfo(&ret, "EXPLAIN,");
+	if (flags & GUC_RUNTIME_COMPUTED)
+		appendStringInfo(&ret, "RUNTIME_COMPUTED,");
+
+	/* Remove trailing comma, if any */
+	if (ret.len > 1)
+		ret.data[--ret.len] = '\0';
+
+	appendStringInfoChar(&ret, '}');
+	return ret.data;
+}
+
 /*
  * Return GUC variable value by variable number; optionally return canonical
  * form of name.  Return value is palloc'd.
@@ -9861,6 +9891,9 @@ GetConfigOptionByNum(int varnum, const char **values, bool *noshow)
 	}
 
 	values[16] = (conf->status & GUC_PENDING_RESTART) ? "t" : "f";
+
+	/* flags */
+	values[17] = get_flags_array_text(conf->flags);
 }
 
 /*
@@ -9916,7 +9949,7 @@ show_config_by_name_missing_ok(PG_FUNCTION_ARGS)
  * show_all_settings - equiv to SHOW ALL command but implemented as
  * a Table Function.
  */
-#define NUM_PG_SETTINGS_ATTS	17
+#define NUM_PG_SETTINGS_ATTS	18
 
 Datum
 show_all_settings(PG_FUNCTION_ARGS)
@@ -9978,6 +10011,8 @@ show_all_settings(PG_FUNCTION_ARGS)
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 17, "pending_restart",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 18, "flags",
+						   TEXTARRAYOID, -1, 0);
 
 		/*
 		 * Generate attribute metadata needed later to produce tuples from raw
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0859dc81cac..1d7f6b4d376 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6092,9 +6092,9 @@
 { oid => '2084', descr => 'SHOW ALL as a function',
   proname => 'pg_show_all_settings', prorows => '1000', proretset => 't',
   provolatile => 's', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool}',
-  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
+  proallargtypes => '{text,text,text,text,text,text,text,text,text,text,text,_text,text,text,text,int4,bool,_text}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart,flags}',
   prosrc => 'show_all_settings' },
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 59da91ff04d..5f15b5680be 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -813,3 +813,125 @@ set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
 ERROR:  tables declared WITH OIDS are not supported
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings();
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ application_name       | Reporting and Logging / What to Log             | f           | f            | t             | f           | f
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------------+--------------------------------------+-------------+--------------+---------------+-------------+--------------
+ default_statistics_target | Query Tuning / Other Planner Options | f           | f            | f             | f           | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ force_parallel_mode | Developer Options                               | f           | f            | t             | t           | f
+ search_path         | Client Connection Defaults / Statement Behavior | f           | f            | f             | t           | f
+(2 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+DROP TABLE pg_settings_flags;
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index d652f7b5fb4..833c1fab6c7 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1725,7 +1725,7 @@ pg_settings| SELECT a.name,
     a.sourcefile,
     a.sourceline,
     a.pending_restart
-   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart);
+   FROM pg_show_all_settings() a(name, setting, unit, category, short_desc, extra_desc, context, vartype, source, min_val, max_val, enumvals, boot_val, reset_val, sourcefile, sourceline, pending_restart, flags);
 pg_shadow| SELECT pg_authid.rolname AS usename,
     pg_authid.oid AS usesysid,
     pg_authid.rolcreatedb AS usecreatedb,
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index c39c11388d5..c3898ae690f 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -311,3 +311,75 @@ reset check_function_bodies;
 set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
+
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings();
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+
+DROP TABLE pg_settings_flags;
-- 
2.17.1

From eee345a1685a04eeb0fedf3ba9ad0fc6fe6e3d81 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH 1/2] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4ff..323ca13191b 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.1

From d09cc770a3e307f55843942a850f7859c63d4c76 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Sun, 5 Dec 2021 23:22:04 -0600
Subject: [PATCH 1/2] check_guc: fix absurd number of false positives

Avoid false positives;
Avoid various assumptions;
Avoid list of exceptions;
Simplify shell/awk/sed/grep;

This requires GNU awk for RS as a regex.
---
 src/backend/utils/misc/check_guc | 69 +++++---------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
index b171ef0e4ff..323ca13191b 100755
--- a/src/backend/utils/misc/check_guc
+++ b/src/backend/utils/misc/check_guc
@@ -1,78 +1,29 @@
-#!/bin/sh
+#! /bin/sh
+set -e
 
-## currently, this script makes a lot of assumptions:
+## this script makes some assumptions about the formatting of files it parses.
 ## in postgresql.conf.sample:
 ##   1) the valid config settings may be preceded by a '#', but NOT '# '
 ##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear
 ### in guc.c?
 
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
+# grab everything that looks like a setting
+SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
 
 for i in $SETTINGS ; do
-  hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
+  grep -i "\"$i\"" guc.c >/dev/null ||
+    echo "$i seems to be missing from guc.c";
 done
 
 ### What options are listed in guc.c, but don't appear
 ### in postgresql.conf.sample?
 
 # grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
+SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
 for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
+  grep "#$i " postgresql.conf.sample >/dev/null ||
+    echo "$i seems to be missing from postgresql.conf.sample";
 done
-- 
2.17.1

From ee2b323f329cc6ff1412bfbc5ad0b64c3584ff03 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 8 Dec 2021 12:06:35 -0600
Subject: [PATCH 2/2] Expose GUC flags in SQL function; retire ./check_guc

---
 doc/src/sgml/func.sgml            |  15 ++++
 src/backend/utils/misc/check_guc  |  29 -------
 src/backend/utils/misc/guc.c      |  37 +++++++++
 src/include/catalog/pg_proc.dat   |   6 ++
 src/include/utils/guc.h           |   3 +-
 src/test/regress/expected/guc.out | 122 ++++++++++++++++++++++++++++++
 src/test/regress/sql/guc.sql      |  72 ++++++++++++++++++
 7 files changed, 254 insertions(+), 30 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 0ee6974f1c6..cbdbccb63d1 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23596,6 +23596,21 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_get_get_flags</primary>
+        </indexterm>
+        <function>pg_get_get_flags</function> ( <parameter>guc</parameter> <type>text</type> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Return an array of flags associated with the given GUC, or NULL if the
+        GUC does not exist.  Not all flags are exposed; the set of flags which
+        are exposed is subject to change.
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index 323ca13191b..00000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,29 +0,0 @@
-#! /bin/sh
-set -e
-
-## this script makes some assumptions about the formatting of files it parses.
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting
-SETTINGS=`sed '/^#[[:alnum:]]/!d; s/^#//; s/ =.*//; /^include/d' postgresql.conf.sample`
-
-for i in $SETTINGS ; do
-  ## it sure would be nice to replace this with an sql "not in" statement
-  grep -i "\"$i\"" guc.c >/dev/null ||
-    echo "$i seems to be missing from guc.c";
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`gawk -F '[",]' 'BEGIN{RS="\n\t\\\\{\n"} /",[[:space:]]*PGC_.*.*gettext_noop/ && !/NOT_IN_SAMPLE/{print tolower($2)}' guc.c`
-for i in $SETTINGS ; do
-  grep "#$i " postgresql.conf.sample >/dev/null ||
-    echo "$i seems to be missing from postgresql.conf.sample";
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 4c94f09c645..d3b56b2007c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9634,6 +9634,43 @@ GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
 	return _ShowOption(record, true);
 }
 
+/*
+ * Return some flags for the specified GUC, or NULL if it doesn't exist.
+ */
+Datum
+pg_get_guc_flags(PG_FUNCTION_ARGS)
+{
+	char *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
+	struct config_generic *record;
+	int			cnt = 0;
+#define MAX_NUM_FLAGS	5
+	Datum      flags[MAX_NUM_FLAGS];
+	ArrayType	*a;
+
+	record = find_option(varname, false, true, ERROR);
+
+	/* return NULL if no such variable */
+	if (record == NULL)
+		PG_RETURN_NULL();
+
+	if (record->flags & GUC_NO_SHOW_ALL)
+		flags[cnt++] = CStringGetTextDatum("NO_SHOW_ALL");
+	if (record->flags & GUC_NO_RESET_ALL)
+		flags[cnt++] = CStringGetTextDatum("NO_RESET_ALL");
+	if (record->flags & GUC_NOT_IN_SAMPLE)
+		flags[cnt++] = CStringGetTextDatum("NOT_IN_SAMPLE");
+	if (record->flags & GUC_EXPLAIN)
+		flags[cnt++] = CStringGetTextDatum("EXPLAIN");
+	if (record->flags & GUC_RUNTIME_COMPUTED)
+		flags[cnt++] = CStringGetTextDatum("RUNTIME_COMPUTED");
+
+	Assert(cnt <= MAX_NUM_FLAGS);
+
+	/* Returns the record as Datum */
+	a = construct_array(flags, cnt, TEXTOID, -1, false, TYPALIGN_INT);
+	PG_RETURN_ARRAYTYPE_P(a);
+}
+
 /*
  * Return GUC variable value by variable number; optionally return canonical
  * form of name.  Return value is palloc'd.
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0859dc81cac..562c1d779cb 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6096,6 +6096,12 @@
   proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
   prosrc => 'show_all_settings' },
+
+{ oid => '8921', descr => 'return flags for specified GUC',
+  proname => 'pg_get_guc_flags', provolatile => 's',
+  prorettype => '_text', proargtypes => 'text',
+  prosrc => 'pg_get_guc_flags' },
+
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 6bb81707b09..1ac20f85ab3 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -198,8 +198,9 @@ typedef enum
 
 #define GUC_QUALIFIER_SEPARATOR '.'
 
-/*
+/* --
  * bit values in "flags" of a GUC variable
+ * Consider if any new flags should be exposed in pg_get_guc_flags().
  */
 #define GUC_LIST_INPUT			0x0001	/* input can be list format */
 #define GUC_LIST_QUOTE			0x0002	/* double-quote list elements */
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 59da91ff04d..29173f3ce8e 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -813,3 +813,125 @@ set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
 ERROR:  tables declared WITH OIDS are not supported
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings() AS psas, pg_get_guc_flags(psas.name) AS flags;
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+            lower            
+-----------------------------
+ config_file
+ plpgsql.check_asserts
+ plpgsql.extra_errors
+ plpgsql.extra_warnings
+ plpgsql.print_strict_params
+ plpgsql.variable_conflict
+(6 rows)
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+        guc        
+-------------------
+ include
+ include_dir
+ include_if_exists
+(3 rows)
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ application_name       | Reporting and Logging / What to Log             | f           | f            | t             | f           | f
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(4 rows)
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+           name            |               category               | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------------+--------------------------------------+-------------+--------------+---------------+-------------+--------------
+ default_statistics_target | Query Tuning / Other Planner Options | f           | f            | f             | f           | f
+(1 row)
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+        name         |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+---------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ force_parallel_mode | Developer Options                               | f           | f            | t             | t           | f
+ search_path         | Client Connection Defaults / Statement Behavior | f           | f            | f             | t           | f
+(2 rows)
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+          name          |                    category                     | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------------------------+-------------------------------------------------+-------------+--------------+---------------+-------------+--------------
+ transaction_deferrable | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_isolation  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+ transaction_read_only  | Client Connection Defaults / Statement Behavior | f           | t            | t             | f           | f
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+ name | category | no_show_all | no_reset_all | not_in_sample | guc_explain | guc_computed 
+------+----------+-------------+--------------+---------------+-------------+--------------
+(0 rows)
+
+DROP TABLE pg_settings_flags;
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index c39c11388d5..47b6a233d5c 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -311,3 +311,75 @@ reset check_function_bodies;
 set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
+
+--
+-- Test GUC categories and flags.
+--
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+	'NO_SHOW_ALL'	=ANY(flags) AS no_show_all,
+	'NO_RESET_ALL'	=ANY(flags) AS no_reset_all,
+	'NOT_IN_SAMPLE'	=ANY(flags) AS not_in_sample,
+	'EXPLAIN'	=ANY(flags) AS guc_explain,
+	'COMPUTED'	=ANY(flags) AS guc_computed
+	FROM pg_show_all_settings() AS psas, pg_get_guc_flags(psas.name) AS flags;
+
+-- test that GUCS are in postgresql.conf
+SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample EXCEPT
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+ORDER BY 1;
+
+-- test that lines in postgresql.conf that look like GUCs are GUCs
+SELECT regexp_replace(ln, '^#?([_[:alpha:]]+) (= .*|[^ ]*$)', '\1') AS guc
+FROM (SELECT regexp_split_to_table(pg_read_file('postgresql.conf'), '\n') AS ln) conf
+WHERE ln ~ '^#?[[:alpha:]]'
+EXCEPT SELECT lower(name) FROM pg_settings_flags WHERE NOT not_in_sample
+ORDER BY 1;
+
+-- test that section:DEVELOPER GUCs are flagged GUC_NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE category='Developer Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE category NOT IN ('Developer Options', 'Preset Options') AND not_in_sample
+ORDER BY 1;
+
+-- Most Query Tuning GUCs are flagged as EXPLAIN:
+SELECT * FROM pg_settings_flags
+WHERE category ~ '^Query Tuning' AND NOT guc_explain
+ORDER BY 1;
+
+-- Maybe the converse:
+SELECT * FROM pg_settings_flags
+WHERE guc_explain AND NOT category ~ '^Query Tuning|^Resource Usage'
+ORDER BY 1;
+
+-- GUCs flagged RUNTIME are Preset
+SELECT * FROM pg_settings_flags
+WHERE guc_computed AND NOT category='Preset Options'
+ORDER BY 1;
+
+-- PRESET GUCs are flagged NOT_IN_SAMPLE
+SELECT * FROM pg_settings_flags
+WHERE category='Preset Options' AND NOT not_in_sample
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NO_RESET_ALL:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT no_reset_all
+ORDER BY 1;
+
+-- Usually the converse:
+SELECT * FROM pg_settings_flags
+WHERE NOT no_show_all AND no_reset_all
+ORDER BY 1;
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT * FROM pg_settings_flags
+WHERE no_show_all AND NOT not_in_sample
+ORDER BY 1;
+
+DROP TABLE pg_settings_flags;
-- 
2.17.1

From a87afcfb5757367aeef795505e9361d5a03facc7 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sat, 29 Jan 2022 15:32:10 +0900
Subject: [PATCH v2] Expose GUC flags in SQL function, replacing check_guc

Note-to-self: CATVERSION bump!
---
 src/include/catalog/pg_proc.dat   |  6 +++
 src/backend/utils/misc/check_guc  | 78 -------------------------------
 src/backend/utils/misc/guc.c      | 39 ++++++++++++++++
 src/test/regress/expected/guc.out | 71 ++++++++++++++++++++++++++++
 src/test/regress/sql/guc.sql      | 41 ++++++++++++++++
 doc/src/sgml/func.sgml            | 39 ++++++++++++++++
 6 files changed, 196 insertions(+), 78 deletions(-)
 delete mode 100755 src/backend/utils/misc/check_guc

diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 0859dc81ca..3f927acb01 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6096,6 +6096,12 @@
   proargmodes => '{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{name,setting,unit,category,short_desc,extra_desc,context,vartype,source,min_val,max_val,enumvals,boot_val,reset_val,sourcefile,sourceline,pending_restart}',
   prosrc => 'show_all_settings' },
+
+{ oid => '8921', descr => 'return flags for specified GUC',
+  proname => 'pg_settings_get_flags', provolatile => 's',
+  prorettype => '_text', proargtypes => 'text',
+  prosrc => 'pg_settings_get_flags' },
+
 { oid => '3329', descr => 'show config file settings',
   proname => 'pg_show_all_file_settings', prorows => '1000', proretset => 't',
   provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/backend/utils/misc/check_guc b/src/backend/utils/misc/check_guc
deleted file mode 100755
index b171ef0e4f..0000000000
--- a/src/backend/utils/misc/check_guc
+++ /dev/null
@@ -1,78 +0,0 @@
-#!/bin/sh
-
-## currently, this script makes a lot of assumptions:
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
-for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
-for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
-done
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 4c94f09c64..b3fd42e0f1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -9634,6 +9634,45 @@ GetConfigOptionByName(const char *name, const char **varname, bool missing_ok)
 	return _ShowOption(record, true);
 }
 
+/*
+ * Return some of the flags associated to the specified GUC in the shape of
+ * a text array, and NULL if it does not exist.  An empty array is returned
+ * if the GUC exists without any meaningful flags to show.
+ */
+Datum
+pg_settings_get_flags(PG_FUNCTION_ARGS)
+{
+#define MAX_GUC_FLAGS	5
+	char	   *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
+	struct config_generic *record;
+	int			cnt = 0;
+	Datum		flags[MAX_GUC_FLAGS];
+	ArrayType  *a;
+
+	record = find_option(varname, false, true, ERROR);
+
+	/* return NULL if no such variable */
+	if (record == NULL)
+		PG_RETURN_NULL();
+
+	if (record->flags & GUC_EXPLAIN)
+		flags[cnt++] = CStringGetTextDatum("EXPLAIN");
+	if (record->flags & GUC_NO_RESET_ALL)
+		flags[cnt++] = CStringGetTextDatum("NO_RESET_ALL");
+	if (record->flags & GUC_NO_SHOW_ALL)
+		flags[cnt++] = CStringGetTextDatum("NO_SHOW_ALL");
+	if (record->flags & GUC_NOT_IN_SAMPLE)
+		flags[cnt++] = CStringGetTextDatum("NOT_IN_SAMPLE");
+	if (record->flags & GUC_RUNTIME_COMPUTED)
+		flags[cnt++] = CStringGetTextDatum("RUNTIME_COMPUTED");
+
+	Assert(cnt <= MAX_GUC_FLAGS);
+
+	/* Returns the record as Datum */
+	a = construct_array(flags, cnt, TEXTOID, -1, false, TYPALIGN_INT);
+	PG_RETURN_ARRAYTYPE_P(a);
+}
+
 /*
  * Return GUC variable value by variable number; optionally return canonical
  * form of name.  Return value is palloc'd.
diff --git a/src/test/regress/expected/guc.out b/src/test/regress/expected/guc.out
index 59da91ff04..5fe53c82e3 100644
--- a/src/test/regress/expected/guc.out
+++ b/src/test/regress/expected/guc.out
@@ -813,3 +813,74 @@ set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
 ERROR:  tables declared WITH OIDS are not supported
+-- Test GUC categories and flag patterns
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+    'EXPLAIN'          = ANY(flags) AS explain,
+    'NO_RESET_ALL'     = ANY(flags) AS no_reset_all,
+    'NO_SHOW_ALL'      = ANY(flags) AS no_show_all,
+    'NOT_IN_SAMPLE'    = ANY(flags) AS not_in_sample,
+    'RUNTIME_COMPUTED' = ANY(flags) AS runtime_computed
+  FROM pg_show_all_settings() AS psas,
+    pg_settings_get_flags(psas.name) AS flags;
+-- Developer GUCs should be flagged with GUC_NOT_IN_SAMPLE:
+SELECT name FROM pg_settings_flags
+  WHERE category = 'Developer Options' AND NOT not_in_sample
+  ORDER BY 1;
+ name 
+------
+(0 rows)
+
+-- Most query-tuning GUCs are flagged as valid for EXPLAIN.
+-- default_statistics_target is an exception.
+SELECT name FROM pg_settings_flags
+  WHERE category ~ '^Query Tuning' AND NOT explain
+  ORDER BY 1;
+           name            
+---------------------------
+ default_statistics_target
+(1 row)
+
+-- Runtime-computed GUCs should be part of the preset category.
+SELECT name FROM pg_settings_flags
+  WHERE NOT category = 'Preset Options' AND runtime_computed
+  ORDER BY 1;
+ name 
+------
+(0 rows)
+
+-- Preset GUCs are flagged as NOT_IN_SAMPLE.
+SELECT name FROM pg_settings_flags
+  WHERE category = 'Preset Options' AND NOT not_in_sample
+  ORDER BY 1;
+ name 
+------
+(0 rows)
+
+-- NO_SHOW_ALL implies NO_RESET_ALL, and vice-versa.
+SELECT name FROM pg_settings_flags
+  WHERE no_show_all AND NOT no_reset_all
+  ORDER BY 1;
+ name 
+------
+(0 rows)
+
+-- Three exceptions as of transaction_*
+SELECT name FROM pg_settings_flags
+  WHERE NOT no_show_all AND no_reset_all
+  ORDER BY 1;
+          name          
+------------------------
+ transaction_deferrable
+ transaction_isolation
+ transaction_read_only
+(3 rows)
+
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT name FROM pg_settings_flags
+  WHERE no_show_all AND NOT not_in_sample
+  ORDER BY 1;
+ name 
+------
+(0 rows)
+
+DROP TABLE pg_settings_flags;
diff --git a/src/test/regress/sql/guc.sql b/src/test/regress/sql/guc.sql
index c39c11388d..7a78b8f3be 100644
--- a/src/test/regress/sql/guc.sql
+++ b/src/test/regress/sql/guc.sql
@@ -311,3 +311,44 @@ reset check_function_bodies;
 set default_with_oids to f;
 -- Should not allow to set it to true.
 set default_with_oids to t;
+
+-- Test GUC categories and flag patterns
+CREATE TABLE pg_settings_flags AS SELECT name, category,
+    'EXPLAIN'          = ANY(flags) AS explain,
+    'NO_RESET_ALL'     = ANY(flags) AS no_reset_all,
+    'NO_SHOW_ALL'      = ANY(flags) AS no_show_all,
+    'NOT_IN_SAMPLE'    = ANY(flags) AS not_in_sample,
+    'RUNTIME_COMPUTED' = ANY(flags) AS runtime_computed
+  FROM pg_show_all_settings() AS psas,
+    pg_settings_get_flags(psas.name) AS flags;
+
+-- Developer GUCs should be flagged with GUC_NOT_IN_SAMPLE:
+SELECT name FROM pg_settings_flags
+  WHERE category = 'Developer Options' AND NOT not_in_sample
+  ORDER BY 1;
+-- Most query-tuning GUCs are flagged as valid for EXPLAIN.
+-- default_statistics_target is an exception.
+SELECT name FROM pg_settings_flags
+  WHERE category ~ '^Query Tuning' AND NOT explain
+  ORDER BY 1;
+-- Runtime-computed GUCs should be part of the preset category.
+SELECT name FROM pg_settings_flags
+  WHERE NOT category = 'Preset Options' AND runtime_computed
+  ORDER BY 1;
+-- Preset GUCs are flagged as NOT_IN_SAMPLE.
+SELECT name FROM pg_settings_flags
+  WHERE category = 'Preset Options' AND NOT not_in_sample
+  ORDER BY 1;
+-- NO_SHOW_ALL implies NO_RESET_ALL, and vice-versa.
+SELECT name FROM pg_settings_flags
+  WHERE no_show_all AND NOT no_reset_all
+  ORDER BY 1;
+-- Three exceptions as of transaction_*
+SELECT name FROM pg_settings_flags
+  WHERE NOT no_show_all AND no_reset_all
+  ORDER BY 1;
+-- NO_SHOW_ALL implies NOT_IN_SAMPLE:
+SELECT name FROM pg_settings_flags
+  WHERE no_show_all AND NOT not_in_sample
+  ORDER BY 1;
+DROP TABLE pg_settings_flags;
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 0ee6974f1c..0cf1ffbcb0 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23596,6 +23596,45 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_get_get_flags</primary>
+        </indexterm>
+        <function>pg_get_get_flags</function> ( <parameter>guc</parameter> <type>text</type> )
+        <returnvalue>text[]</returnvalue>
+       </para>
+       <para>
+        Returns an array of the flags associated with the given GUC, or
+        <literal>NULL</literal> if the  does not exist.  The result is
+        an empty array if the GUC exists but there are no flags to show,
+        as supported by the list below.
+        The following flags are exposed (the most meaningful ones are
+        included):
+        <simplelist>
+         <member>
+          <literal>EXPLAIN</literal>, parameters included in
+          <command>EXPLAIN</command> commands.
+         </member>
+         <member>
+          <literal>NO_SHOW_ALL</literal>, parameters excluded from
+          <command>SHOW ALL</command> commands.
+         </member>
+         <member>
+          <literal>NO_RESET_ALL</literal>, parameters excluded from
+          <command>RESET ALL</command> commands.
+         </member>
+         <member>
+          <literal>NOT_IN_SAMPLE</literal>, parameters not included in
+          <filename>postgresql.conf</filename> by default.
+         </member>
+         <member>
+          <literal>RUNTIME_COMPUTED</literal>, runtime-computed parameters.
+         </member>
+        </simplelist>
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
-- 
2.34.1

From 5c3fbf6af5111927aa7a61025abfce87a9bd230e Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Mon, 7 Feb 2022 11:32:17 +0900
Subject: [PATCH] Add TAP test to automate check_guc

---
 src/test/modules/test_misc/t/003_check_guc.pl | 77 +++++++++++++++++++
 src/test/perl/PostgreSQL/Test/Cluster.pm      | 25 ++++++
 2 files changed, 102 insertions(+)
 create mode 100644 src/test/modules/test_misc/t/003_check_guc.pl

diff --git a/src/test/modules/test_misc/t/003_check_guc.pl b/src/test/modules/test_misc/t/003_check_guc.pl
new file mode 100644
index 0000000000..cd64fb8b49
--- /dev/null
+++ b/src/test/modules/test_misc/t/003_check_guc.pl
@@ -0,0 +1,77 @@
+# Tests to cross-check the consistency of GUC parameters with
+# postgresql.conf.sample.
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->start;
+
+# Grab the names of all the parameters that can be listed in the
+# configuration sample file.
+my $all_params = $node->safe_psql(
+	'postgres',
+	"SELECT name
+     FROM pg_settings
+   WHERE NOT 'NOT_IN_SAMPLE' = ANY (pg_settings_get_flags(name))
+     ORDER BY 1");
+# Note the lower-case conversion, for consistency.
+my @all_params_array = split("\n", lc($all_params));
+
+# Grab the names of all parameters marked as NOT_IN_SAMPLE.
+my $not_in_sample = $node->safe_psql(
+	'postgres',
+	"SELECT name
+     FROM pg_settings
+   WHERE 'NOT_IN_SAMPLE' = ANY (pg_settings_get_flags(name))
+     ORDER BY 1");
+# Note the lower-case conversion, for consistency.
+my @not_in_sample_array = split("\n", lc($not_in_sample));
+
+# Find the location of postgresql.conf.sample, based on the information
+# provided by pg_config.
+my $sample_file =
+  $node->config_data('--sharedir') . '/postgresql.conf.sample';
+
+# Read the sample file line-by-line, checking its contents.
+my $num_tests = 0;
+open(my $contents, '<', $sample_file)
+  || die "Could not open $sample_file: $!";
+while (my $line = <$contents>)
+{
+	# Check if this line matches a GUC parameter.
+	if ($line =~ m/^#?([_[:alpha:]]+) (= .*|[^ ]*$)/)
+	{
+		# Lower-case conversion matters for some of the GUCs.
+		my $param_name = lc($1);
+
+		# Ignore some exceptions.
+		next if $param_name eq "include";
+		next if $param_name eq "include_dir";
+		next if $param_name eq "include_if_exists";
+
+		my $marked_all_params = grep(/^$param_name$/, @all_params_array);
+		my $marked_not_in_sample =
+		  grep(/^$param_name$/, @not_in_sample_array);
+
+		# All parameters marked as NOT_IN_SAMPLE cannot be in
+		# the sample file.
+		is($marked_not_in_sample, 0,
+			"checked $param_name not marked with NOT_IN_SAMPLE");
+		# All parameters *not* marked as NOT_IN_SAMPLE can be
+		# in the sample file.
+		is($marked_all_params, 1,
+			"checked $param_name in postgresql.conf.sample");
+
+		# Update test count.
+		$num_tests += 2;
+	}
+}
+
+close $contents;
+
+plan tests => $num_tests;
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 265f3ae657..832d119f2e 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -327,6 +327,31 @@ sub install_path
 
 =pod
 
+=item $node->config_data($option)
+
+Grab some data from pg_config, with $option being the option switch
+used to grab the wanted data.
+
+=cut
+
+sub config_data
+{
+	my ($self, $option) = @_;
+	local %ENV = $self->_get_env();
+
+	my ($stdout, $stderr);
+	my $result =
+	  IPC::Run::run [ $self->installed_command('pg_config'), $option ],
+	  '>', \$stdout, '2>', \$stderr
+	  or die "could not execute pg_config";
+	chomp($stdout);
+	$stdout =~ s/\r$//;
+
+	return $stdout;
+}
+
+=pod
+
 =item $node->info()
 
 Return a string containing human-readable diagnostic information (paths, etc)
-- 
2.34.1

From dd9f0cb34960e89dd1ea5c12ab03ee1bc6884e1f Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 8 Feb 2022 10:10:42 +0900
Subject: [PATCH v2] Add TAP test to automate check_guc

---
 src/test/modules/test_misc/t/003_check_guc.pl | 105 ++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 src/test/modules/test_misc/t/003_check_guc.pl

diff --git a/src/test/modules/test_misc/t/003_check_guc.pl b/src/test/modules/test_misc/t/003_check_guc.pl
new file mode 100644
index 0000000000..01f954e09c
--- /dev/null
+++ b/src/test/modules/test_misc/t/003_check_guc.pl
@@ -0,0 +1,105 @@
+# Tests to cross-check the consistency of GUC parameters with
+# postgresql.conf.sample.
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More tests => 3;
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->start;
+
+# Grab the names of all the parameters that can be listed in the
+# configuration sample file.  config_file is an exception.  It is not
+# in postgresql.conf.sample but is part of the lists from guc.c.
+my $all_params = $node->safe_psql(
+	'postgres',
+	"SELECT name
+     FROM pg_settings
+   WHERE NOT 'NOT_IN_SAMPLE' = ANY (pg_settings_get_flags(name)) AND
+       name <> 'config_file'
+     ORDER BY 1");
+# Note the lower-case conversion, for consistency.
+my @all_params_array = split("\n", lc($all_params));
+
+# Grab the names of all parameters marked as NOT_IN_SAMPLE.
+my $not_in_sample = $node->safe_psql(
+	'postgres',
+	"SELECT name
+     FROM pg_settings
+   WHERE 'NOT_IN_SAMPLE' = ANY (pg_settings_get_flags(name))
+     ORDER BY 1");
+# Note the lower-case conversion, for consistency.
+my @not_in_sample_array = split("\n", lc($not_in_sample));
+
+# Find the location of postgresql.conf.sample, based on the information
+# provided by pg_config.
+my $sample_file =
+  $node->config_data('--sharedir') . '/postgresql.conf.sample';
+
+# List of all the GUCs found in the sample file.
+my @gucs_in_file;
+
+# Read the sample file line-by-line, checking its contents to build a list
+# of everything known as a GUC.
+my $num_tests = 0;
+open(my $contents, '<', $sample_file)
+  || die "Could not open $sample_file: $!";
+while (my $line = <$contents>)
+{
+	# Check if this line matches a GUC parameter.
+	if ($line =~ m/^#?([_[:alpha:]]+) (= .*|[^ ]*$)/)
+	{
+		# Lower-case conversion matters for some of the GUCs.
+		my $param_name = lc($1);
+
+		# Ignore some exceptions.
+		next if $param_name eq "include";
+		next if $param_name eq "include_dir";
+		next if $param_name eq "include_if_exists";
+
+		# Update the list of GUCs found in the sample file, for the
+		# follow-up tests.
+		push @gucs_in_file, $param_name;
+	}
+}
+
+close $contents;
+
+# Cross-check that all the GUCs found in the sample file match the ones
+# fetched above.  This maps the arrays to a hash, making the creation of
+# each exclude and intersection list easier.
+my %gucs_in_file_hash  = map { $_ => 1 } @gucs_in_file;
+my %all_params_hash    = map { $_ => 1 } @all_params_array;
+my %not_in_sample_hash = map { $_ => 1 } @not_in_sample_array;
+
+my @missing_from_file = grep(!$gucs_in_file_hash{$_}, @all_params_array);
+is(scalar(@missing_from_file),
+	0, "no parameters missing from postgresql.conf.sample");
+
+my @missing_from_list = grep(!$all_params_hash{$_}, @gucs_in_file);
+is(scalar(@missing_from_list), 0, "no parameters missing from guc.c");
+
+my @sample_intersect = grep($not_in_sample_hash{$_}, @gucs_in_file);
+is(scalar(@sample_intersect),
+	0, "no parameters marked as NOT_IN_SAMPLE in postgresql.conf.sample");
+
+# These would log some information only on errors.
+foreach my $param (@missing_from_file)
+{
+	print("found GUC $param in guc.c, missing from postgresql.conf.sample\n");
+}
+foreach my $param (@missing_from_list)
+{
+	print(
+		"found GUC $param in postgresql.conf.sample, with incorrect info in guc.c\n"
+	);
+}
+foreach my $param (@sample_intersect)
+{
+	print(
+		"found GUC $param in postgresql.conf.sample, marked as NOT_IN_SAMPLE\n"
+	);
+}
-- 
2.34.1