Date: Sat, 17 Sep 2022 23:53:07 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: michael@paquier.xyz, andres@anarazel.de, nathandbossart@gmail.com,
	pgsql-hackers@postgresql.org
Subject: Re: fix stats_fetch_consistency value in postgresql.conf.sample
Message-ID: <20220918045306.GT31833@telsasoft.com>
References: <20220713173000.GD18011@telsasoft.com>
 <Ys9ZOk49mruHPn4q@paquier.xyz>
 <20220713235444.GF18011@telsasoft.com>
 <20220719.150427.952514686871468436.horikyota.ntt@gmail.com>
 <20220720051226.GH12702@telsasoft.com>
 <20220728222734.GA1913@telsasoft.com>
 <20220913004303.GM31833@telsasoft.com>
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This is an alternative implementation, which still relies on adding the
GUC_DYNAMIC, flag but doesn't require adding a new, sql-accessible
function to convert the GUC to a pretty/human display value.

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Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
 filename="0001-add-DYNAMIC_DEFAULT-for-settings-which-vary-by-.-con.patch"

From 25ee6d6ed23ff273e622551fd033c8d086953fe5 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Tue, 19 Jul 2022 08:31:56 -0500
Subject: [PATCH 1/2] add DYNAMIC_DEFAULT for settings which vary by
 ./configure or platform or initdb

---
 doc/src/sgml/func.sgml              |  8 ++++++
 src/backend/utils/misc/guc_funcs.c  |  4 ++-
 src/backend/utils/misc/guc_tables.c | 39 ++++++++++++++++-------------
 src/include/utils/guc.h             |  2 ++
 4 files changed, 35 insertions(+), 18 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 67eb3806326..63063d054c5 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -24341,6 +24341,14 @@ SELECT collation for ('foo' COLLATE "de_DE");
      <row><entry>Flag</entry><entry>Description</entry></row>
     </thead>
     <tbody>
+
+     <row>
+      <entry><literal>DYNAMIC_DEFAULT</literal></entry>
+      <entry>Parameters with this flag have default values which vary by
+      platform, or compile-time options, or are set dynamically during initdb.
+      </entry>
+     </row>
+
      <row>
       <entry><literal>EXPLAIN</literal></entry>
       <entry>Parameters with this flag are included in
diff --git a/src/backend/utils/misc/guc_funcs.c b/src/backend/utils/misc/guc_funcs.c
index 3d2df18659b..3376f23e076 100644
--- a/src/backend/utils/misc/guc_funcs.c
+++ b/src/backend/utils/misc/guc_funcs.c
@@ -539,7 +539,7 @@ ShowAllGUCConfig(DestReceiver *dest)
 Datum
 pg_settings_get_flags(PG_FUNCTION_ARGS)
 {
-#define MAX_GUC_FLAGS	5
+#define MAX_GUC_FLAGS	6
 	char	   *varname = TextDatumGetCString(PG_GETARG_DATUM(0));
 	struct config_generic *record;
 	int			cnt = 0;
@@ -552,6 +552,8 @@ pg_settings_get_flags(PG_FUNCTION_ARGS)
 	if (record == NULL)
 		PG_RETURN_NULL();
 
+	if (record->flags & GUC_DYNAMIC_DEFAULT)
+		flags[cnt++] = CStringGetTextDatum("DYNAMIC_DEFAULT");
 	if (record->flags & GUC_EXPLAIN)
 		flags[cnt++] = CStringGetTextDatum("EXPLAIN");
 	if (record->flags & GUC_NO_RESET_ALL)
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 7bff45e10d6..bd3c84bc7b8 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1201,7 +1201,7 @@ struct config_bool ConfigureNamesBool[] =
 		{"debug_assertions", PGC_INTERNAL, PRESET_OPTIONS,
 			gettext_noop("Shows whether the running server has assertion checks enabled."),
 			NULL,
-			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
+			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_DYNAMIC_DEFAULT
 		},
 		&assert_enabled,
 #ifdef USE_ASSERT_CHECKING
@@ -1377,7 +1377,8 @@ struct config_bool ConfigureNamesBool[] =
 	{
 		{"update_process_title", PGC_SUSET, PROCESS_TITLE,
 			gettext_noop("Updates the process title to show the active SQL command."),
-			gettext_noop("Enables updating of the process title every time a new SQL command is received by the server.")
+			gettext_noop("Enables updating of the process title every time a new SQL command is received by the server."),
+			GUC_DYNAMIC_DEFAULT
 		},
 		&update_process_title,
 #ifdef WIN32
@@ -2126,7 +2127,8 @@ struct config_int ConfigureNamesInt[] =
 	{
 		{"max_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
 			gettext_noop("Sets the maximum number of concurrent connections."),
-			NULL
+			NULL,
+			GUC_DYNAMIC_DEFAULT
 		},
 		&MaxConnections,
 		100, 1, MAX_BACKENDS,
@@ -2163,7 +2165,7 @@ struct config_int ConfigureNamesInt[] =
 		{"shared_buffers", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Sets the number of shared memory buffers used by the server."),
 			NULL,
-			GUC_UNIT_BLOCKS
+			GUC_UNIT_BLOCKS | GUC_DYNAMIC_DEFAULT
 		},
 		&NBuffers,
 		16384, 16, INT_MAX / 2,
@@ -2677,7 +2679,7 @@ struct config_int ConfigureNamesInt[] =
 		{"checkpoint_flush_after", PGC_SIGHUP, WAL_CHECKPOINTS,
 			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
 			NULL,
-			GUC_UNIT_BLOCKS
+			GUC_UNIT_BLOCKS | GUC_DYNAMIC_DEFAULT
 		},
 		&checkpoint_flush_after,
 		DEFAULT_CHECKPOINT_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
@@ -2895,7 +2897,7 @@ struct config_int ConfigureNamesInt[] =
 		{"bgwriter_flush_after", PGC_SIGHUP, RESOURCES_BGWRITER,
 			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
 			NULL,
-			GUC_UNIT_BLOCKS
+			GUC_UNIT_BLOCKS | GUC_DYNAMIC_DEFAULT
 		},
 		&bgwriter_flush_after,
 		DEFAULT_BGWRITER_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
@@ -2908,7 +2910,7 @@ struct config_int ConfigureNamesInt[] =
 			RESOURCES_ASYNCHRONOUS,
 			gettext_noop("Number of simultaneous requests that can be handled efficiently by the disk subsystem."),
 			NULL,
-			GUC_EXPLAIN
+			GUC_EXPLAIN | GUC_DYNAMIC_DEFAULT
 		},
 		&effective_io_concurrency,
 #ifdef USE_PREFETCH
@@ -2926,7 +2928,7 @@ struct config_int ConfigureNamesInt[] =
 			RESOURCES_ASYNCHRONOUS,
 			gettext_noop("A variant of effective_io_concurrency that is used for maintenance work."),
 			NULL,
-			GUC_EXPLAIN
+			GUC_EXPLAIN | GUC_DYNAMIC_DEFAULT
 		},
 		&maintenance_io_concurrency,
 #ifdef USE_PREFETCH
@@ -2943,7 +2945,7 @@ struct config_int ConfigureNamesInt[] =
 		{"backend_flush_after", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
 			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
 			NULL,
-			GUC_UNIT_BLOCKS
+			GUC_UNIT_BLOCKS | GUC_DYNAMIC_DEFAULT
 		},
 		&backend_flush_after,
 		DEFAULT_BACKEND_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
@@ -3397,7 +3399,7 @@ struct config_int ConfigureNamesInt[] =
 		{"debug_discard_caches", PGC_SUSET, DEVELOPER_OPTIONS,
 			gettext_noop("Aggressively flush system caches for debugging purposes."),
 			NULL,
-			GUC_NOT_IN_SAMPLE
+			GUC_NOT_IN_SAMPLE | GUC_DYNAMIC_DEFAULT
 		},
 		&debug_discard_caches,
 #ifdef DISCARD_CACHES_ENABLED
@@ -4224,7 +4226,7 @@ struct config_string ConfigureNamesString[] =
 		{"unix_socket_directories", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
 			gettext_noop("Sets the directories where Unix-domain sockets will be created."),
 			NULL,
-			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY
+			GUC_LIST_INPUT | GUC_LIST_QUOTE | GUC_SUPERUSER_ONLY | GUC_DYNAMIC_DEFAULT
 		},
 		&Unix_socket_directories,
 		DEFAULT_PGSOCKET_DIR,
@@ -4305,7 +4307,7 @@ struct config_string ConfigureNamesString[] =
 		{"ssl_library", PGC_INTERNAL, PRESET_OPTIONS,
 			gettext_noop("Shows the name of the SSL library."),
 			NULL,
-			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
+			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_DYNAMIC_DEFAULT
 		},
 		&ssl_library,
 #ifdef USE_SSL
@@ -4391,7 +4393,7 @@ struct config_string ConfigureNamesString[] =
 		{"ssl_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
 			gettext_noop("Sets the list of allowed SSL ciphers."),
 			NULL,
-			GUC_SUPERUSER_ONLY
+			GUC_SUPERUSER_ONLY | GUC_DYNAMIC_DEFAULT
 		},
 		&SSLCipherSuites,
 #ifdef USE_OPENSSL
@@ -4406,7 +4408,7 @@ struct config_string ConfigureNamesString[] =
 		{"ssl_ecdh_curve", PGC_SIGHUP, CONN_AUTH_SSL,
 			gettext_noop("Sets the curve to use for ECDH."),
 			NULL,
-			GUC_SUPERUSER_ONLY
+			GUC_SUPERUSER_ONLY | GUC_DYNAMIC_DEFAULT
 		},
 		&SSLECDHCurve,
 #ifdef USE_SSL
@@ -4644,7 +4646,8 @@ struct config_enum ConfigureNamesEnum[] =
 	{
 		{"syslog_facility", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the syslog \"facility\" to be used when syslog enabled."),
-			NULL
+			NULL,
+			GUC_DYNAMIC_DEFAULT
 		},
 		&syslog_facility,
 #ifdef HAVE_SYSLOG
@@ -4757,7 +4760,8 @@ struct config_enum ConfigureNamesEnum[] =
 	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
-			NULL
+			NULL,
+			GUC_DYNAMIC_DEFAULT
 		},
 		&dynamic_shared_memory_type,
 		DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE, dynamic_shared_memory_options,
@@ -4777,7 +4781,8 @@ struct config_enum ConfigureNamesEnum[] =
 	{
 		{"wal_sync_method", PGC_SIGHUP, WAL_SETTINGS,
 			gettext_noop("Selects the method used for forcing WAL updates to disk."),
-			NULL
+			NULL,
+			GUC_DYNAMIC_DEFAULT
 		},
 		&sync_method,
 		DEFAULT_SYNC_METHOD, sync_method_options,
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index e426dd757d9..0447d3eb56a 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -238,6 +238,8 @@ typedef enum
  */
 #define GUC_RUNTIME_COMPUTED  0x200000
 
+#define GUC_DYNAMIC_DEFAULT		  0x400000	/* default value is dynamic */
+
 #define GUC_UNIT				(GUC_UNIT_MEMORY | GUC_UNIT_TIME)
 
 
-- 
2.25.1


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Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
 filename="0002-WIP-test-guc-default-values.patch"

From d7940be9ac7f1e4d29b6651a315c8dbfc54f84e2 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Wed, 25 May 2022 05:14:43 -0500
Subject: [PATCH 2/2] WIP: test guc default values

---
 src/backend/utils/misc/postgresql.conf.sample |  2 +-
 src/test/modules/test_misc/t/003_check_guc.pl | 32 +++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 8a0b383eb71..88a033103d1 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -721,7 +721,7 @@
 					# share/timezonesets/.
 #extra_float_digits = 1			# min -15, max 3; any value >0 actually
 					# selects precise output mode
-#client_encoding = sql_ascii		# actually, defaults to database
+#client_encoding = SQL_ASCII		# actually, defaults to database
 					# encoding
 
 # These settings are initialized by initdb, but they can be changed.
diff --git a/src/test/modules/test_misc/t/003_check_guc.pl b/src/test/modules/test_misc/t/003_check_guc.pl
index 60459ef759e..dd5ac2c8bc4 100644
--- a/src/test/modules/test_misc/t/003_check_guc.pl
+++ b/src/test/modules/test_misc/t/003_check_guc.pl
@@ -107,4 +107,36 @@ foreach my $param (@sample_intersect)
 	);
 }
 
+# Test that GUCs in postgresql.conf.sample show the correct default values
+my $check_defaults = $node->safe_psql(
+	'postgres',
+	"
+	CREATE TABLE sample_conf AS
+	SELECT m[1] AS name, COALESCE(m[3], m[5]) AS sample_value
+	FROM (SELECT regexp_split_to_table(pg_read_file('../../../$sample_file'), '\n') AS ln) conf,
+	regexp_match(ln, '^#?([_[:alpha:]]+) (= ''([^'']*)''|(= ([^[:space:]]*))).*') AS m
+	WHERE ln ~ '^#?[[:alpha:]]'
+	");
+
+$check_defaults = $node->safe_psql(
+	'postgres',
+	"
+	SELECT name, current_setting(name), sc.sample_value, boot_val
+	FROM pg_show_all_settings() psas
+	JOIN sample_conf sc USING(name)
+	WHERE sc.sample_value != boot_val -- same value
+	AND sc.sample_value != current_setting(name) -- same value, with human units
+	AND sc.sample_value != current_setting(name)||'.0' -- same value with .0 suffix
+	AND 'DYNAMIC_DEFAULT' != ALL(pg_settings_get_flags(psas.name)) -- dynamically-set defaults
+	AND NOT (sc.sample_value ~ '^0' AND current_setting(name) ~ '^0') -- zeros may be written differently
+	AND NOT (sc.sample_value='60s' AND current_setting(name) = '1min') -- two ways to write 1min
+	AND name NOT IN ('krb_server_keyfile', 'wal_retrieve_retry_interval', 'log_autovacuum_min_duration'); -- exceptions
+	");
+
+my @check_defaults_array = split("\n", lc($check_defaults));
+print(STDERR "$check_defaults\n");
+
+is (@check_defaults_array, 0,
+	'check for consistency of defaults in postgresql.conf.sample');
+
 done_testing();
-- 
2.25.1


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