diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 8896988e5aa9a8f53e6b81190bb13f6e1a08b4ee..f0794467ba47c748717cfb99b65061818d9038ff 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1944,6 +1944,32 @@ include 'filename'
</listitem>
</varlistentry>
+ <varlistentry id="guc-wal-log-hintbits" xreflabel="wal_log_hintbits">
+ <term><varname>wal_log_hintbits</varname> (<type>boolean</type>)</term>
+ <indexterm>
+ <primary><varname>wal_log_hintbits</> configuration parameter</primary>
+ </indexterm>
+ <listitem>
+ <para>
+ When this parameter is <literal>on</>, the <productname>PostgreSQL</>
+ server writes the entire content of each disk page to WAL during the
+ first modification of that page after a checkpoint, even for
+ non-critical modifications of so-called hint bits.
+ </para>
+
+ <para>
+ If data checksums are enabled, hint bit updates are always WAL-logged
+ and this setting is ignored. You can use this setting to test how much
+ extra WAL-logging would occur if your database had data checksums
+ enabled.
+ </para>
+
+ <para>
+ This parameter can only be set at server start. The default value is <literal>off</>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-wal-buffers" xreflabel="wal_buffers">
<term><varname>wal_buffers</varname> (<type>integer</type>)</term>
<indexterm>
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 09174b472b06a00b6aa74db9b7f1690e7a34eafb..91cfae1603d674632b2376a5d4bbb895e20fb89e 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6271,7 +6271,7 @@ log_heap_visible(RelFileNode rnode, Buffer heap_buffer, Buffer vm_buffer,
rdata[1].buffer_std = false;
rdata[1].next = NULL;
- if (DataChecksumsEnabled())
+ if (XLogHintBitIsNeeded())
{
rdata[1].next = &(rdata[2]);
diff --git a/src/backend/access/heap/visibilitymap.c b/src/backend/access/heap/visibilitymap.c
index 7f40d89b9f1ac722772ec52325333cd4c0f6ae95..60ee76a208133f55b419f8e0993836bcf89e0540 100644
--- a/src/backend/access/heap/visibilitymap.c
+++ b/src/backend/access/heap/visibilitymap.c
@@ -287,10 +287,10 @@ visibilitymap_set(Relation rel, BlockNumber heapBlk, Buffer heapBuf,
cutoff_xid);
/*
- * If data checksums are enabled, we need to protect the heap
- * page from being torn.
+ * If data checksums are enabled (or wal_log_hintbits=on), we
+ * need to protect the heap page from being torn.
*/
- if (DataChecksumsEnabled())
+ if (XLogHintBitIsNeeded())
{
Page heapPage = BufferGetPage(heapBuf);
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a76aef37f3d2f6066153fa6080d0183efe224390..0efb50b17ef9669a977d9dd4a4592a476bbb75c8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -79,6 +79,7 @@ bool XLogArchiveMode = false;
char *XLogArchiveCommand = NULL;
bool EnableHotStandby = false;
bool fullPageWrites = true;
+bool walLogHintbits = false;
bool log_checkpoints = false;
int sync_method = DEFAULT_SYNC_METHOD;
int wal_level = WAL_LEVEL_MINIMAL;
@@ -5270,6 +5271,7 @@ BootStrapXLOG(void)
ControlFile->max_prepared_xacts = max_prepared_xacts;
ControlFile->max_locks_per_xact = max_locks_per_xact;
ControlFile->wal_level = wal_level;
+ ControlFile->wal_log_hintbits = walLogHintbits;
ControlFile->data_checksum_version = bootstrap_data_checksum_version;
/* some additional ControlFile fields are set in WriteControlFile() */
@@ -9058,6 +9060,7 @@ static void
XLogReportParameters(void)
{
if (wal_level != ControlFile->wal_level ||
+ walLogHintbits != ControlFile->wal_log_hintbits ||
MaxConnections != ControlFile->MaxConnections ||
max_worker_processes != ControlFile->max_worker_processes ||
max_prepared_xacts != ControlFile->max_prepared_xacts ||
@@ -9080,6 +9083,7 @@ XLogReportParameters(void)
xlrec.max_prepared_xacts = max_prepared_xacts;
xlrec.max_locks_per_xact = max_locks_per_xact;
xlrec.wal_level = wal_level;
+ xlrec.wal_log_hintbits = walLogHintbits;
rdata.buffer = InvalidBuffer;
rdata.data = (char *) &xlrec;
@@ -9094,6 +9098,7 @@ XLogReportParameters(void)
ControlFile->max_prepared_xacts = max_prepared_xacts;
ControlFile->max_locks_per_xact = max_locks_per_xact;
ControlFile->wal_level = wal_level;
+ ControlFile->wal_log_hintbits = walLogHintbits;
UpdateControlFile();
}
}
@@ -9480,6 +9485,7 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts;
ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact;
ControlFile->wal_level = xlrec.wal_level;
+ ControlFile->wal_log_hintbits = walLogHintbits;
/*
* Update minRecoveryPoint to ensure that if recovery is aborted, we
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index f84839181161e2aaedf3ef6a806d0647116ab5c0..081165faef09484f607562e0ec6fb8650859389e 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -2626,16 +2626,15 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
bool delayChkpt = false;
/*
- * If checksums are enabled, and the buffer is permanent, then a full
- * page image may be required even for some hint bit updates to
- * protect against torn pages. This full page image is only necessary
+ * If we need to protect hint bit updates from torn writes, WAL-log a
+ * full page image of the page. This full page image is only necessary
* if the hint bit update is the first change to the page since the
* last checkpoint.
*
* We don't check full_page_writes here because that logic is included
* when we call XLogInsert() since the value changes dynamically.
*/
- if (DataChecksumsEnabled() && (bufHdr->flags & BM_PERMANENT))
+ if (XLogHintBitIsNeeded() && (bufHdr->flags & BM_PERMANENT))
{
/*
* If we're in recovery we cannot dirty a page because of a hint.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index e69e132f056288d5bcb0fe3f6d230a7e6256b3a4..b0c14a2dfce41b1631e15ce3b26c6b5feaeb49e9 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -866,6 +866,17 @@ static struct config_bool ConfigureNamesBool[] =
true,
NULL, NULL, NULL
},
+
+ {
+ {"wal_log_hintbits", PGC_POSTMASTER, WAL_SETTINGS,
+ gettext_noop("Writes full pages to WAL when first modified after a checkpoint, even for a non-critical modifications"),
+ NULL
+ },
+ &walLogHintbits,
+ false,
+ NULL, NULL, NULL
+ },
+
{
{"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
gettext_noop("Logs each checkpoint."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f8bdce34d3307aba3cbadf152525b95286835a11..d049159444f481815be4ac180e649ea5eae31696 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -184,6 +184,7 @@
# fsync_writethrough
# open_sync
#full_page_writes = on # recover from partial page writes
+#wal_log_hintbits = off # also do full pages writes of non-critical updates
#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/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c
index 8c6cf24d23755217d400536a5c26ac21efea6d36..da48e98ff99282236f83b36ed0a7ecbff19f32fe 100644
--- a/src/bin/pg_controldata/pg_controldata.c
+++ b/src/bin/pg_controldata/pg_controldata.c
@@ -260,6 +260,8 @@ main(int argc, char *argv[])
ControlFile.backupEndRequired ? _("yes") : _("no"));
printf(_("Current wal_level setting: %s\n"),
wal_level_str(ControlFile.wal_level));
+ printf(_("Current wal_log_hintbits setting: %s\n"),
+ ControlFile.wal_log_hintbits ? _("on") : _("off"));
printf(_("Current max_connections setting: %d\n"),
ControlFile.MaxConnections);
printf(_("Current max_worker_processes setting: %d\n"),
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index ed0f945679649d3bd21d5c2b65e3660b87824e50..da13ff4d134b7c185b3c62af6cc6eeec9f2ab31e 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -525,6 +525,7 @@ GuessControlValues(void)
/* minRecoveryPoint, backupStartPoint and backupEndPoint can be left zero */
ControlFile.wal_level = WAL_LEVEL_MINIMAL;
+ ControlFile.wal_log_hintbits = false;
ControlFile.MaxConnections = 100;
ControlFile.max_worker_processes = 8;
ControlFile.max_prepared_xacts = 0;
@@ -721,6 +722,7 @@ RewriteControlFile(void)
* anyway at startup.
*/
ControlFile.wal_level = WAL_LEVEL_MINIMAL;
+ ControlFile.wal_log_hintbits = false;
ControlFile.MaxConnections = 100;
ControlFile.max_worker_processes = 8;
ControlFile.max_prepared_xacts = 0;
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 7415a261bbdfe0c673a0c6f5985cbce4489c160c..e69accd4b2e010fce8376fe31729d13d8b0f04ee 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -189,6 +189,7 @@ extern bool XLogArchiveMode;
extern char *XLogArchiveCommand;
extern bool EnableHotStandby;
extern bool fullPageWrites;
+extern bool walLogHintbits;
extern bool log_checkpoints;
extern int num_xloginsert_slots;
@@ -211,6 +212,17 @@ extern int wal_level;
*/
#define XLogIsNeeded() (wal_level >= WAL_LEVEL_ARCHIVE)
+/*
+ * Is a full-page image needed for hint bit updates?
+ *
+ * Normally, we don't WAL-log hint bit updates, but if checksums are enabled,
+ * we have to protect them against torn page writes. When you only set
+ * individual bits on a page, it's still consistent no matter what combination
+ * of the bits make it to disk, but the checksum wouldn't match. Also WAL-log
+ * them if forced by wal_log_hintbits=on.
+ */
+#define XLogHintBitIsNeeded() (DataChecksumsEnabled() || walLogHintbits)
+
/* Do we need to WAL-log information required only for Hot Standby and logical replication? */
#define XLogStandbyInfoActive() (wal_level >= WAL_LEVEL_HOT_STANDBY)
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 64ba55355b9857184a1679fca4850bb700df2ca8..c78a2fbfae8f0668bb14555402de22bc5863e8a5 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -209,6 +209,7 @@ typedef struct xl_parameter_change
int max_prepared_xacts;
int max_locks_per_xact;
int wal_level;
+ bool wal_log_hintbits;
} xl_parameter_change;
/* logs restore point */
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 759395a24b942be8480456b0bf85f37f6025d847..b7610e8c3f86a12bad4923bc09efd4703f4e365c 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
*/
/* yyyymmddN */
-#define CATALOG_VERSION_NO 201311261
+#define CATALOG_VERSION_NO 201312131
#endif
diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.h
index 637221e6347c1e673a24675176dce751caa9d872..8f23508ad0f16a6dd2bc337cbe18eef2b0836efc 100644
--- a/src/include/catalog/pg_control.h
+++ b/src/include/catalog/pg_control.h
@@ -171,6 +171,7 @@ typedef struct ControlFileData
* or hot standby.
*/
int wal_level;
+ bool wal_log_hintbits;
int MaxConnections;
int max_worker_processes;
int max_prepared_xacts;