0001_add_statistics_to_pg_stat_wal_view.patch

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 6656676..31a37de 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3406,12 +3406,95 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
     </thead>
 
     <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_records</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL records generated
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_fpi</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL full page images generated
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_bytes</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total amount of WAL bytes generated
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>wal_buffers_full</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of times WAL data was written to the disk because WAL buffers got full
+       Total number of WAL data written to the disk because WAL buffers got full
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_init</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL file segment created or opened a pre-existing one
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_init_zero</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL file segment created to be filled with zeroes
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_write</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL data written to the disk
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_write_time</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       WAL data was written to disk, in milliseconds
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_sync</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total number of WAL data synced to the disk
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>wal_sync_time</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Total amount of time that has been spent in the portion of
+       WAL data was synced to disk, in milliseconds
       </para></entry>
      </row>
 
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 52a67b1..840e684 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -1262,6 +1262,10 @@ XLogInsertRecord(XLogRecData *rdata,
 		pgWalUsage.wal_bytes += rechdr->xl_tot_len;
 		pgWalUsage.wal_records++;
 		pgWalUsage.wal_fpi += num_fpi;
+
+		WalStats.m_wal_bytes += rechdr->xl_tot_len;
+		WalStats.m_wal_records++;
+		WalStats.m_wal_fpi += num_fpi;
 	}
 
 	return EndPos;
@@ -2422,6 +2426,10 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 	int			npages;
 	int			startidx;
 	uint32		startoffset;
+	TimestampTz start_time;
+	TimestampTz end_time;
+	long		secs;
+	int			usecs;
 
 	/* We should always be inside a critical section here */
 	Assert(CritSectionCount > 0);
@@ -2535,9 +2543,11 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 			do
 			{
 				errno = 0;
+				start_time = GetCurrentTimestamp();
 				pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE);
 				written = pg_pwrite(openLogFile, from, nleft, startoffset);
 				pgstat_report_wait_end();
+				end_time = GetCurrentTimestamp();
 				if (written <= 0)
 				{
 					char		xlogfname[MAXFNAMELEN];
@@ -2559,6 +2569,13 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 				nleft -= written;
 				from += written;
 				startoffset += written;
+
+				/* Accumulate write time in milliseconds. */
+				TimestampDifference(start_time,
+									end_time,
+									&secs, &usecs);
+				WalStats.m_wal_write_time += ((int) secs * 1000) + (usecs / 1000);
+				WalStats.m_wal_write++;
 			} while (nleft > 0);
 
 			npages = 0;
@@ -2578,7 +2595,16 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 			 */
 			if (finishing_seg)
 			{
+				start_time = GetCurrentTimestamp();
 				issue_xlog_fsync(openLogFile, openLogSegNo);
+				end_time = GetCurrentTimestamp();
+
+				/* Accumulate write time in milliseconds. */
+				TimestampDifference(start_time,
+									end_time,
+									&secs, &usecs);
+				WalStats.m_wal_sync_time += ((int) secs * 1000) + (usecs / 1000);
+				WalStats.m_wal_sync++;
 
 				/* signal that we need to wakeup walsenders later */
 				WalSndWakeupRequest();
@@ -2649,7 +2675,16 @@ XLogWrite(XLogwrtRqst WriteRqst, bool flexible)
 				ReserveExternalFD();
 			}
 
+			start_time = GetCurrentTimestamp();
 			issue_xlog_fsync(openLogFile, openLogSegNo);
+			end_time = GetCurrentTimestamp();
+
+			/* Accumulate write time in milliseconds. */
+			TimestampDifference(start_time,
+								end_time,
+								&secs, &usecs);
+			WalStats.m_wal_sync_time += ((int) secs * 1000) + (usecs / 1000);
+			WalStats.m_wal_sync++;
 		}
 
 		/* signal that we need to wakeup walsenders later */
@@ -3278,7 +3313,10 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 						 errmsg("could not open file \"%s\": %m", path)));
 		}
 		else
+		{
+			WalStats.m_wal_init++;
 			return fd;
+		}
 	}
 
 	/*
@@ -3325,6 +3363,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 				break;
 			}
 		}
+		WalStats.m_wal_init_zero++;
 	}
 	else
 	{
@@ -3418,6 +3457,7 @@ XLogFileInit(XLogSegNo logsegno, bool *use_existent, bool use_lock)
 				 errmsg("could not open file \"%s\": %m", path)));
 
 	elog(DEBUG2, "done creating and filling new WAL file");
+	WalStats.m_wal_init++;
 
 	return fd;
 }
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index c293907..b880533 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -990,7 +990,16 @@ CREATE VIEW pg_stat_bgwriter AS
 
 CREATE VIEW pg_stat_wal AS
     SELECT
+        w.wal_records,
+        w.wal_fpi,
+        w.wal_bytes,
         w.wal_buffers_full,
+        w.wal_init,
+        w.wal_init_zero,
+        w.wal_write,
+        w.wal_write_time,
+        w.wal_sync,
+        w.wal_sync_time,
         w.stats_reset
     FROM pg_stat_get_wal() w;
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 822f0eb..2cf85b6 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -6756,7 +6756,16 @@ pgstat_recv_bgwriter(PgStat_MsgBgWriter *msg, int len)
 static void
 pgstat_recv_wal(PgStat_MsgWal *msg, int len)
 {
+	walStats.wal_records += msg->m_wal_records;
+	walStats.wal_fpi += msg->m_wal_fpi;
+	walStats.wal_bytes += msg->m_wal_bytes;
 	walStats.wal_buffers_full += msg->m_wal_buffers_full;
+	walStats.wal_init += msg->m_wal_init;
+	walStats.wal_init_zero += msg->m_wal_init_zero;
+	walStats.wal_write += msg->m_wal_write;
+	walStats.wal_write_time += msg->m_wal_write_time;
+	walStats.wal_sync += msg->m_wal_sync;
+	walStats.wal_sync_time += msg->m_wal_sync_time;
 }
 
 /* ----------
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index a52832f..ce9f4b7 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -253,6 +253,9 @@ WalWriterMain(void)
 		else if (left_till_hibernate > 0)
 			left_till_hibernate--;
 
+		/* Send WAL statistics */
+		pgstat_send_wal();
+
 		/*
 		 * Sleep until we are signaled or WalWriterDelay has elapsed.  If we
 		 * haven't done anything useful for quite some time, lengthen the
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 0d0d2e6..8ed25d7 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1703,7 +1703,7 @@ pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_wal(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_WAL_COLS	2
+#define PG_STAT_GET_WAL_COLS	11
 	TupleDesc	tupdesc;
 	Datum		values[PG_STAT_GET_WAL_COLS];
 	bool		nulls[PG_STAT_GET_WAL_COLS];
@@ -1715,9 +1715,27 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
 
 	/* Initialise attributes information in the tuple descriptor */
 	tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_WAL_COLS);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "wal_buffers_full",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "wal_records",
 					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "stats_reset",
+	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "wal_fpi",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "wal_bytes",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "wal_buffers_full",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "wal_init",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "wal_init_zero",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "wal_write",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "wal_write_time",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "wal_sync",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "wal_sync_time",
+					   INT8OID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "stats_reset",
 					   TIMESTAMPTZOID, -1, 0);
 
 	BlessTupleDesc(tupdesc);
@@ -1726,8 +1744,17 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
 	wal_stats = pgstat_fetch_stat_wal();
 
 	/* Fill values and NULLs */
-	values[0] = Int64GetDatum(wal_stats->wal_buffers_full);
-	values[1] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
+	values[0] = Int64GetDatum(wal_stats->wal_records);
+	values[1] = Int64GetDatum(wal_stats->wal_fpi);
+	values[2] = Int64GetDatum(wal_stats->wal_bytes);
+	values[3] = Int64GetDatum(wal_stats->wal_buffers_full);
+	values[4] = Int64GetDatum(wal_stats->wal_init);
+	values[5] = Int64GetDatum(wal_stats->wal_init_zero);
+	values[6] = Int64GetDatum(wal_stats->wal_write);
+	values[7] = Int64GetDatum(wal_stats->wal_write_time);
+	values[8] = Int64GetDatum(wal_stats->wal_sync);
+	values[9] = Int64GetDatum(wal_stats->wal_sync_time);
+	values[10] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
 
 	/* Returns the record as Datum */
 	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 22340ba..ee55eb1 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5492,9 +5492,9 @@
 { oid => '1136', descr => 'statistics: information about WAL activity',
   proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => '',
-  proallargtypes => '{int8,timestamptz}',
-  proargmodes => '{o,o}',
-  proargnames => '{wal_buffers_full,stats_reset}',
+  proallargtypes => '{int8,int8,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,wal_init,wal_init_zero,wal_write,wal_write_time,wal_sync,wal_sync_time,stats_reset}',
   prosrc => 'pg_stat_get_wal' },
 
 { oid => '2306', descr => 'statistics: information about SLRU caches',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index a821ff4..b35ae99 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -459,7 +459,16 @@ typedef struct PgStat_MsgBgWriter
 typedef struct PgStat_MsgWal
 {
 	PgStat_MsgHdr m_hdr;
+	PgStat_Counter m_wal_records;
+	PgStat_Counter m_wal_fpi;
+	PgStat_Counter m_wal_bytes;
 	PgStat_Counter m_wal_buffers_full;
+	PgStat_Counter m_wal_init;
+	PgStat_Counter m_wal_init_zero;
+	PgStat_Counter m_wal_write;
+	PgStat_Counter m_wal_write_time;	/* accumulate times in milliseconds */
+	PgStat_Counter m_wal_sync;
+	PgStat_Counter m_wal_sync_time; /* accumulate times in milliseconds */
 } PgStat_MsgWal;
 
 /* ----------
@@ -795,7 +804,22 @@ typedef struct PgStat_GlobalStats
  */
 typedef struct PgStat_WalStats
 {
+	PgStat_Counter wal_records;
+	PgStat_Counter wal_fpi;
+	PgStat_Counter wal_bytes;
 	PgStat_Counter wal_buffers_full;
+	PgStat_Counter wal_init;
+	PgStat_Counter wal_init_zero;
+
+	/*
+	 * TODO: Is it better to separate following metrics
+	 * for backends and background processes?
+	 */
+	PgStat_Counter wal_write;
+	PgStat_Counter wal_write_time;
+	PgStat_Counter wal_sync;
+	PgStat_Counter wal_sync_time;
+
 	TimestampTz stat_reset_timestamp;
 } PgStat_WalStats;
 
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index cf2a9b4..b15f04c 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2135,9 +2135,18 @@ pg_stat_user_tables| SELECT pg_stat_all_tables.relid,
     pg_stat_all_tables.autoanalyze_count
    FROM pg_stat_all_tables
   WHERE ((pg_stat_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'information_schema'::name])) AND (pg_stat_all_tables.schemaname !~ '^pg_toast'::text));
-pg_stat_wal| SELECT w.wal_buffers_full,
+pg_stat_wal| SELECT w.wal_records,
+    w.wal_fpi,
+    w.wal_bytes,
+    w.wal_buffers_full,
+    w.wal_init,
+    w.wal_init_zero,
+    w.wal_write,
+    w.wal_write_time,
+    w.wal_sync,
+    w.wal_sync_time,
     w.stats_reset
-   FROM pg_stat_get_wal() w(wal_buffers_full, stats_reset);
+   FROM pg_stat_get_wal() w(wal_records, wal_fpi, wal_bytes, wal_buffers_full, wal_init, wal_init_zero, wal_write, wal_write_time, wal_sync, wal_sync_time, stats_reset);
 pg_stat_wal_receiver| SELECT s.pid,
     s.status,
     s.receive_start_lsn,