From dbdfd114f34443f1e4ad16ce2721f9817d3b3d80 Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Fri, 25 Nov 2016 18:36:10 -0500
Subject: Bring some clarity to the defaults for the xxx_flush_after
 parameters.

Instead of confusingly stating platform-dependent defaults for these
parameters in the comments in postgresql.conf.sample (with the main
entry being a lie on Linux), teach initdb to install the correct
platform-dependent value in postgresql.conf, similarly to the way
we handle other platform-dependent defaults.  This won't do anything
for existing 9.6 installations, but since it's effectively only a
documentation improvement, that seems OK.

Since this requires initdb to have access to the default values,
move the #define's for those to pg_config_manual.h; the original
placement in bufmgr.h is unworkable because that file can't be
included by frontend programs.

Adjust the default value for wal_writer_flush_after so that it is 1MB
regardless of XLOG_BLCKSZ, conforming to what is stated in both the
SGML docs and postgresql.conf.  (We could alternatively make it scale
with XLOG_BLCKSZ, but I'm not sure I see the point.)

Copy-edit related SGML documentation.

Fabien Coelho and Tom Lane, per a gripe from Tomas Vondra.

Discussion: <30ebc6e3-8358-09cf-44a8-578252938424@2ndquadrant.com>
---
 src/bin/initdb/initdb.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

(limited to 'src/bin/initdb')

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index c8a8c52c3d7..24f9cc8eae2 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -64,11 +64,11 @@
 #include "common/file_utils.h"
 #include "common/restricted_token.h"
 #include "common/username.h"
-#include "mb/pg_wchar.h"
+#include "fe_utils/string_utils.h"
 #include "getaddrinfo.h"
 #include "getopt_long.h"
+#include "mb/pg_wchar.h"
 #include "miscadmin.h"
-#include "fe_utils/string_utils.h"
 
 
 /* Ideally this would be in a .h file, but it hardly seems worth the trouble */
@@ -1095,6 +1095,27 @@ setup_config(void)
 	conflines = replace_token(conflines, "#dynamic_shared_memory_type = posix",
 							  repltok);
 
+#if DEFAULT_BACKEND_FLUSH_AFTER > 0
+	snprintf(repltok, sizeof(repltok), "#backend_flush_after = %dkB",
+			 DEFAULT_BACKEND_FLUSH_AFTER * (BLCKSZ / 1024));
+	conflines = replace_token(conflines, "#backend_flush_after = 0",
+							  repltok);
+#endif
+
+#if DEFAULT_BGWRITER_FLUSH_AFTER > 0
+	snprintf(repltok, sizeof(repltok), "#bgwriter_flush_after = %dkB",
+			 DEFAULT_BGWRITER_FLUSH_AFTER * (BLCKSZ / 1024));
+	conflines = replace_token(conflines, "#bgwriter_flush_after = 0",
+							  repltok);
+#endif
+
+#if DEFAULT_CHECKPOINT_FLUSH_AFTER > 0
+	snprintf(repltok, sizeof(repltok), "#checkpoint_flush_after = %dkB",
+			 DEFAULT_CHECKPOINT_FLUSH_AFTER * (BLCKSZ / 1024));
+	conflines = replace_token(conflines, "#checkpoint_flush_after = 0",
+							  repltok);
+#endif
+
 #ifndef USE_PREFETCH
 	conflines = replace_token(conflines,
 							  "#effective_io_concurrency = 1",
-- 
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