Sync guc.c and postgresql.conf.sample with the SGML docs.

It seems that various people have moved GUCs around in the config.sgml
listing without bothering to make the code agree.  Ensure that the
config_group codes assigned to GUCs match where they are listed in
config.sgml.  Likewise ensure that postgresql.conf.sample lists GUCs
in the same sub-section and same ordering as they appear in config.sgml.

(I've got some doubts about some of these choices, but for the purposes
of this patch, we'll treat config.sgml as gospel.)

Notably, this requires adding a WAL_RECOVERY config_group value,
because 1d25757 didn't.  As long as we're renumbering that enum
anyway, let's take out the values corresponding to major groups
that are divided into sub-groups.  No GUC should be assigned to the
major group itself, so those values just create a temptation to
do the wrong thing, while adding work for translators.

In passing, adjust the short_desc strings for PRESET_OPTIONS GUCs
to uniformly use the phrasing "Shows XYZ.", removing the impression
some of these strings left that you can set the value.

While some of these errors are old, no back-patch, as changing the
contents of the pg_settings view in stable branches seems more likely
to be seen as a compatibility break than anything helpful.

Bharath Rupireddy, Justin Pryzby, Tom Lane

Discussion: https://postgr.es/m/16997-ff16127f6e0d1390@postgresql.org
Discussion: https://postgr.es/m/20210413123139.GE6091@telsasoft.com

Author: tglsfdc

src/backend/utils/misc/guc.c

@@ -703,16 +703,12 @@ const char *const config_group_names[] =
 	gettext_noop("Ungrouped"),
 	/* FILE_LOCATIONS */
 	gettext_noop("File Locations"),
-	/* CONN_AUTH */
-	gettext_noop("Connections and Authentication"),
 	/* CONN_AUTH_SETTINGS */
 	gettext_noop("Connections and Authentication / Connection Settings"),
 	/* CONN_AUTH_AUTH */
 	gettext_noop("Connections and Authentication / Authentication"),
 	/* CONN_AUTH_SSL */
 	gettext_noop("Connections and Authentication / SSL"),
-	/* RESOURCES */
-	gettext_noop("Resource Usage"),
 	/* RESOURCES_MEM */
 	gettext_noop("Resource Usage / Memory"),
 	/* RESOURCES_DISK */
@@ -725,20 +721,18 @@ const char *const config_group_names[] =
 	gettext_noop("Resource Usage / Background Writer"),
 	/* RESOURCES_ASYNCHRONOUS */
 	gettext_noop("Resource Usage / Asynchronous Behavior"),
-	/* WAL */
-	gettext_noop("Write-Ahead Log"),
 	/* WAL_SETTINGS */
 	gettext_noop("Write-Ahead Log / Settings"),
 	/* WAL_CHECKPOINTS */
 	gettext_noop("Write-Ahead Log / Checkpoints"),
 	/* WAL_ARCHIVING */
 	gettext_noop("Write-Ahead Log / Archiving"),
+	/* WAL_RECOVERY */
+	gettext_noop("Write-Ahead Log / Recovery"),
 	/* WAL_ARCHIVE_RECOVERY */
 	gettext_noop("Write-Ahead Log / Archive Recovery"),
 	/* WAL_RECOVERY_TARGET */
 	gettext_noop("Write-Ahead Log / Recovery Target"),
-	/* REPLICATION */
-	gettext_noop("Replication"),
 	/* REPLICATION_SENDING */
 	gettext_noop("Replication / Sending Servers"),
 	/* REPLICATION_PRIMARY */
@@ -747,8 +741,6 @@ const char *const config_group_names[] =
 	gettext_noop("Replication / Standby Servers"),
 	/* REPLICATION_SUBSCRIBERS */
 	gettext_noop("Replication / Subscribers"),
-	/* QUERY_TUNING */
-	gettext_noop("Query Tuning"),
 	/* QUERY_TUNING_METHOD */
 	gettext_noop("Query Tuning / Planner Method Configuration"),
 	/* QUERY_TUNING_COST */
@@ -757,26 +749,20 @@ const char *const config_group_names[] =
 	gettext_noop("Query Tuning / Genetic Query Optimizer"),
 	/* QUERY_TUNING_OTHER */
 	gettext_noop("Query Tuning / Other Planner Options"),
-	/* LOGGING */
-	gettext_noop("Reporting and Logging"),
 	/* LOGGING_WHERE */
 	gettext_noop("Reporting and Logging / Where to Log"),
 	/* LOGGING_WHEN */
 	gettext_noop("Reporting and Logging / When to Log"),
 	/* LOGGING_WHAT */
 	gettext_noop("Reporting and Logging / What to Log"),
 	/* PROCESS_TITLE */
-	gettext_noop("Process Title"),
-	/* STATS */
-	gettext_noop("Statistics"),
+	gettext_noop("Reporting and Logging / Process Title"),
 	/* STATS_MONITORING */
 	gettext_noop("Statistics / Monitoring"),
 	/* STATS_COLLECTOR */
 	gettext_noop("Statistics / Query and Index Statistics Collector"),
 	/* AUTOVACUUM */
 	gettext_noop("Autovacuum"),
-	/* CLIENT_CONN */
-	gettext_noop("Client Connection Defaults"),
 	/* CLIENT_CONN_STATEMENT */
 	gettext_noop("Client Connection Defaults / Statement Behavior"),
 	/* CLIENT_CONN_LOCALE */
@@ -787,8 +773,6 @@ const char *const config_group_names[] =
 	gettext_noop("Client Connection Defaults / Other Defaults"),
 	/* LOCK_MANAGEMENT */
 	gettext_noop("Lock Management"),
-	/* COMPAT_OPTIONS */
-	gettext_noop("Version and Platform Compatibility"),
 	/* COMPAT_OPTIONS_PREVIOUS */
 	gettext_noop("Version and Platform Compatibility / Previous PostgreSQL Versions"),
 	/* COMPAT_OPTIONS_CLIENT */
@@ -1188,7 +1172,7 @@ static struct config_bool ConfigureNamesBool[] =
 		check_bonjour, NULL, NULL
 	},
 	{
-		{"track_commit_timestamp", PGC_POSTMASTER, REPLICATION,
+		{"track_commit_timestamp", PGC_POSTMASTER, REPLICATION_SENDING,
 			gettext_noop("Collects transaction commit time."),
 			NULL
 		},
@@ -1297,7 +1281,7 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 	{
-		{"recovery_prefetch", PGC_SIGHUP, WAL_SETTINGS,
+		{"recovery_prefetch", PGC_SIGHUP, WAL_RECOVERY,
 			gettext_noop("Prefetch referenced blocks during recovery."),
 			gettext_noop("Read ahead of the current replay position to find uncached blocks.")
 		},
@@ -1306,7 +1290,7 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, assign_recovery_prefetch, NULL
 	},
 	{
-		{"recovery_prefetch_fpw", PGC_SIGHUP, WAL_SETTINGS,
+		{"recovery_prefetch_fpw", PGC_SIGHUP, WAL_RECOVERY,
 			gettext_noop("Prefetch blocks that have full page images in the WAL."),
 			gettext_noop("On some systems, there is no benefit to prefetching pages that will be "
 						 "entirely overwritten, but if the logical page size of the filesystem is "
@@ -1869,7 +1853,7 @@ static struct config_bool ConfigureNamesBool[] =
 
 	{
 		{"integer_datetimes", PGC_INTERNAL, PRESET_OPTIONS,
-			gettext_noop("Datetimes are integer based."),
+			gettext_noop("Shows whether datetimes are integer based."),
 			NULL,
 			GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
 		},
@@ -2416,7 +2400,7 @@ static struct config_int ConfigureNamesInt[] =
 
 	{
 		{"data_directory_mode", PGC_INTERNAL, PRESET_OPTIONS,
-			gettext_noop("Mode of the data directory."),
+			gettext_noop("Shows the mode of the data directory."),
 			gettext_noop("The parameter value is a numeric mode specification "
 						 "in the form accepted by the chmod and umask system "
 						 "calls. (To use the customary octal format the number "
@@ -2772,7 +2756,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"wal_decode_buffer_size", PGC_POSTMASTER, WAL_ARCHIVE_RECOVERY,
+		{"wal_decode_buffer_size", PGC_POSTMASTER, WAL_RECOVERY,
 			gettext_noop("Maximum buffer size for reading ahead in the WAL during recovery."),
 			gettext_noop("This controls the maximum distance we can read ahead in the WAL to prefetch referenced blocks."),
 			GUC_UNIT_BYTE
@@ -3393,7 +3377,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"tcp_keepalives_idle", PGC_USERSET, CLIENT_CONN_OTHER,
+		{"tcp_keepalives_idle", PGC_USERSET, CONN_AUTH_SETTINGS,
 			gettext_noop("Time between issuing TCP keepalives."),
 			gettext_noop("A value of 0 uses the system default."),
 			GUC_UNIT_S
@@ -3404,7 +3388,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"tcp_keepalives_interval", PGC_USERSET, CLIENT_CONN_OTHER,
+		{"tcp_keepalives_interval", PGC_USERSET, CONN_AUTH_SETTINGS,
 			gettext_noop("Time between TCP keepalive retransmits."),
 			gettext_noop("A value of 0 uses the system default."),
 			GUC_UNIT_S
@@ -3426,7 +3410,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"tcp_keepalives_count", PGC_USERSET, CLIENT_CONN_OTHER,
+		{"tcp_keepalives_count", PGC_USERSET, CONN_AUTH_SETTINGS,
 			gettext_noop("Maximum number of TCP keepalive retransmits."),
 			gettext_noop("This controls the number of consecutive keepalive retransmits that can be "
 						 "lost before a connection is considered dead. A value of 0 uses the "
@@ -3506,7 +3490,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"track_activity_query_size", PGC_POSTMASTER, RESOURCES_MEM,
+		{"track_activity_query_size", PGC_POSTMASTER, STATS_COLLECTOR,
 			gettext_noop("Sets the size reserved for pg_stat_activity.query, in bytes."),
 			NULL,
 			GUC_UNIT_BYTE
@@ -3528,7 +3512,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"tcp_user_timeout", PGC_USERSET, CLIENT_CONN_OTHER,
+		{"tcp_user_timeout", PGC_USERSET, CONN_AUTH_SETTINGS,
 			gettext_noop("TCP user timeout."),
 			gettext_noop("A value of 0 uses the system default."),
 			GUC_UNIT_MS
@@ -3573,7 +3557,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"client_connection_check_interval", PGC_USERSET, CLIENT_CONN_OTHER,
+		{"client_connection_check_interval", PGC_USERSET, CONN_AUTH_SETTINGS,
 			gettext_noop("Sets the time interval between checks for disconnection while running queries."),
 			NULL,
 			GUC_UNIT_MS
@@ -4102,7 +4086,7 @@ static struct config_string ConfigureNamesString[] =
 	/* See main.c about why defaults for LC_foo are not all alike */
 
 	{
-		{"lc_collate", PGC_INTERNAL, CLIENT_CONN_LOCALE,
+		{"lc_collate", PGC_INTERNAL, PRESET_OPTIONS,
 			gettext_noop("Shows the collation order locale."),
 			NULL,
 			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
@@ -4113,7 +4097,7 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"lc_ctype", PGC_INTERNAL, CLIENT_CONN_LOCALE,
+		{"lc_ctype", PGC_INTERNAL, PRESET_OPTIONS,
 			gettext_noop("Shows the character classification and case conversion locale."),
 			NULL,
 			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
@@ -4209,8 +4193,8 @@ static struct config_string ConfigureNamesString[] =
 
 	{
 		/* Can't be set in postgresql.conf */
-		{"server_encoding", PGC_INTERNAL, CLIENT_CONN_LOCALE,
-			gettext_noop("Sets the server (database) character set encoding."),
+		{"server_encoding", PGC_INTERNAL, PRESET_OPTIONS,
+			gettext_noop("Shows the server (database) character set encoding."),
 			NULL,
 			GUC_IS_NAME | GUC_REPORT | GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
 		},
@@ -4429,7 +4413,7 @@ static struct config_string ConfigureNamesString[] =
 
 	{
 		{"ssl_library", PGC_INTERNAL, PRESET_OPTIONS,
-			gettext_noop("Name of the SSL library."),
+			gettext_noop("Shows the name of the SSL library."),
 			NULL,
 			GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
 		},