Fix documentation & config inconsistencies around 428b1d6b2.

Several issues:
1) checkpoint_flush_after doc and code disagreed about the default
2) new GUCs were missing from postgresql.conf.sample
3) Outdated source-code comment about bgwriter_flush_after's default
4) Sub-optimal categories assigned to new GUCs
5) Docs suggested backend_flush_after is PGC_SIGHUP, but it's PGC_USERSET.
6) Spell out int as integer in the docs, as done elsewhere

Reported-By: Magnus Hagander, Fujii Masao
Discussion: CAHGQGwETyTG5VYQQ5C_srwxWX7RXvFcD3dKROhvAWWhoSBdmZw@mail.gmail.com

2 files changed, 31 insertions, 25 deletions

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index fb091bc4a0b..60856dda198 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2274,6 +2274,18 @@ static 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
+		},
+		&checkpoint_flush_after,
+		/* see bufmgr.h: OS dependent default */
+		DEFAULT_CHECKPOINT_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"wal_buffers", PGC_POSTMASTER, WAL_SETTINGS,
 			gettext_noop("Sets the number of disk-page buffers in shared memory for WAL."),
 			NULL,
@@ -2420,6 +2432,18 @@ static 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
+		},
+		&bgwriter_flush_after,
+		/* see bufmgr.h: OS dependent default */
+		DEFAULT_BGWRITER_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"effective_io_concurrency",
 			PGC_USERSET,
 			RESOURCES_ASYNCHRONOUS,
@@ -2436,19 +2460,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"checkpoint_flush_after", PGC_SIGHUP, RESOURCES_ASYNCHRONOUS,
-			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
-			NULL,
-			GUC_UNIT_BLOCKS
-		},
-		&checkpoint_flush_after,
-		/* see bufmgr.h: OS dependent default */
-		DEFAULT_CHECKPOINT_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
-		NULL, NULL, NULL
-	},
-
-	{
-		{"backend_flush_after", PGC_USERSET, WAL_CHECKPOINTS,
+		{"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
@@ -2460,18 +2472,6 @@ static struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"bgwriter_flush_after", PGC_SIGHUP, WAL_CHECKPOINTS,
-			gettext_noop("Number of pages after which previously performed writes are flushed to disk."),
-			NULL,
-			GUC_UNIT_BLOCKS
-		},
-		&bgwriter_flush_after,
-		/* see bufmgr.h: 16 on Linux, 0 otherwise */
-		DEFAULT_BGWRITER_FLUSH_AFTER, 0, WRITEBACK_MAX_PENDING_FLUSHES,
-		NULL, NULL, NULL
-	},
-
-	{
 		{"max_worker_processes",
 			PGC_POSTMASTER,
 			RESOURCES_ASYNCHRONOUS,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index d4dd285ef0a..14b537ffb17 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -160,6 +160,8 @@
 #bgwriter_delay = 200ms			# 10-10000ms between rounds
 #bgwriter_lru_maxpages = 100		# 0-1000 max buffers written/round
 #bgwriter_lru_multiplier = 2.0		# 0-10.0 multiplier on buffers scanned/round
+#bgwriter_flush_after = 0		# 0 disables,
+					# default is 512kb on linux, 0 otherwise
 
 # - Asynchronous Behavior -
 
@@ -168,6 +170,8 @@
 #max_parallel_degree = 0		# max number of worker processes per node
 #old_snapshot_threshold = -1		# 1min-60d; -1 disables; 0 is immediate
 									# (change requires restart)
+#backend_flush_after = 0		# 0 disables,
+					# default is 128kb on linux, 0 otherwise
 
 
 #------------------------------------------------------------------------------
@@ -206,6 +210,8 @@
 #max_wal_size = 1GB
 #min_wal_size = 80MB
 #checkpoint_completion_target = 0.5	# checkpoint target duration, 0.0 - 1.0
+#checkpoint_flush_after = 0		# 0 disables,
+					# default is 256kb on linux, 0 otherwise
 #checkpoint_warning = 30s		# 0 disables
 
 # - Archiving -