From f5ce48e45aa79edc4e61fb6c6128dde6cacbd0c6 Mon Sep 17 00:00:00 2001
From: Jerry Jelinek <jerry.jelinek@joyent.com>
Date: Tue, 26 Jun 2018 11:45:12 +0000
Subject: [PATCH] option to disable WAL recycling

---
 doc/src/sgml/config.sgml                      | 22 ++++++++++++++++++++++
 src/backend/access/transam/xlog.c             |  3 ++-
 src/backend/utils/misc/guc.c                  | 10 ++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/access/xlog.h                     |  1 +
 5 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7bfbc87..457db77 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3116,6 +3116,28 @@ include_dir 'conf.d'
        </listitem>
       </varlistentry>
 
+     <varlistentry id="guc-wal-recycle" xreflabel="wal_recycle">
+      <term><varname>wal_recycle</varname> (<type>boolean</type>)
+      <indexterm>
+       <primary><varname>wal_recycle</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        When this parameter is <literal>on</literal>, past log file segments
+        in the <filename>pg_wal</filename> directory are recycled for future
+        use.
+       </para>
+
+       <para>
+        Turning this parameter off causes past log files segments to be deleted
+        when no longer needed. This can improve performance by eliminating
+        read-modify-write operations on old files which are no longer in the
+        filesystem cache.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
       <term><varname>wal_sender_timeout</varname> (<type>integer</type>)
       <indexterm>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 1a419aa..74427c5 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -99,6 +99,7 @@ bool		wal_log_hints = false;
 bool		wal_compression = false;
 char	   *wal_consistency_checking_string = NULL;
 bool	   *wal_consistency_checking = NULL;
+bool		wal_recycle = true;
 bool		log_checkpoints = false;
 int			sync_method = DEFAULT_SYNC_METHOD;
 int			wal_level = WAL_LEVEL_MINIMAL;
@@ -4012,7 +4013,7 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 	 * segment. Only recycle normal files, pg_standby for example can create
 	 * symbolic links pointing to a separate archive directory.
 	 */
-	if (endlogSegNo <= recycleSegNo &&
+	if (wal_recycle && endlogSegNo <= recycleSegNo &&
 		lstat(path, &statbuf) == 0 && S_ISREG(statbuf.st_mode) &&
 		InstallXLogFileSegment(&endlogSegNo, path,
 							   true, recycleSegNo, true))
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 859ef93..18ede0d 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1114,6 +1114,16 @@ static struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
+		{"wal_recycle", PGC_SUSET, WAL_SETTINGS,
+			gettext_noop("WAL recycling enabled."),
+			NULL
+		},
+		&wal_recycle,
+		true,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
 			gettext_noop("Logs each checkpoint."),
 			NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 9e39baf..474fd7b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -199,6 +199,7 @@
 #wal_compression = off			# enable compression of full-page writes
 #wal_log_hints = off			# also do full page writes of non-critical updates
 					# (change requires restart)
+#wal_recycle = off			# do not recycle WAL files
 #wal_buffers = -1			# min 32kB, -1 sets based on shared_buffers
 					# (change requires restart)
 #wal_writer_delay = 200ms		# 1-10000 milliseconds
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 421ba6d..cf13f12 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -106,6 +106,7 @@ extern bool EnableHotStandby;
 extern bool fullPageWrites;
 extern bool wal_log_hints;
 extern bool wal_compression;
+extern bool wal_recycle;
 extern bool *wal_consistency_checking;
 extern char *wal_consistency_checking_string;
 extern bool log_checkpoints;
-- 
2.2.1