Add pg_stat_wal statistics view.

This view shows the statistics about WAL activity. Currently it has only
two columns: wal_buffers_full and stats_reset. wal_buffers_full column
indicates the number of times WAL data was written to the disk because
WAL buffers got full. This information is useful when tuning wal_buffers.
stats_reset column indicates the time at which these statistics were
last reset.

pg_stat_wal view is also the basic infrastructure to expose other
various statistics about WAL activity later.

Bump PGSTAT_FILE_FORMAT_ID due to the change in pgstat format.

Bump catalog version.

Author: Masahiro Ikeda
Reviewed-by: Takayuki Tsunakawa, Kyotaro Horiguchi, Amit Kapila, Fujii Masao
Discussion: https://postgr.es/m/[email protected]

1 files changed, 31 insertions, 2 deletions

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0dfbac46b4b..343eef507ea 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -61,6 +61,7 @@ typedef enum StatMsgType
 	PGSTAT_MTYPE_ANALYZE,
 	PGSTAT_MTYPE_ARCHIVER,
 	PGSTAT_MTYPE_BGWRITER,
+	PGSTAT_MTYPE_WAL,
 	PGSTAT_MTYPE_SLRU,
 	PGSTAT_MTYPE_FUNCSTAT,
 	PGSTAT_MTYPE_FUNCPURGE,
@@ -122,7 +123,8 @@ typedef struct PgStat_TableCounts
 typedef enum PgStat_Shared_Reset_Target
 {
 	RESET_ARCHIVER,
-	RESET_BGWRITER
+	RESET_BGWRITER,
+	RESET_WAL
 } PgStat_Shared_Reset_Target;
 
 /* Possible object types for resetting single counters */
@@ -437,6 +439,16 @@ typedef struct PgStat_MsgBgWriter
 } PgStat_MsgBgWriter;
 
 /* ----------
+ * PgStat_MsgWal			Sent by backends and background processes to update WAL statistics.
+ * ----------
+ */
+typedef struct PgStat_MsgWal
+{
+	PgStat_MsgHdr m_hdr;
+	PgStat_Counter m_wal_buffers_full;
+} PgStat_MsgWal;
+
+/* ----------
  * PgStat_MsgSLRU			Sent by a backend to update SLRU statistics.
  * ----------
  */
@@ -596,6 +608,7 @@ typedef union PgStat_Msg
 	PgStat_MsgAnalyze msg_analyze;
 	PgStat_MsgArchiver msg_archiver;
 	PgStat_MsgBgWriter msg_bgwriter;
+	PgStat_MsgWal msg_wal;
 	PgStat_MsgSLRU msg_slru;
 	PgStat_MsgFuncstat msg_funcstat;
 	PgStat_MsgFuncpurge msg_funcpurge;
@@ -614,7 +627,7 @@ typedef union PgStat_Msg
  * ------------------------------------------------------------
  */
 
-#define PGSTAT_FILE_FORMAT_ID	0x01A5BC9D
+#define PGSTAT_FILE_FORMAT_ID	0x01A5BC9E
 
 /* ----------
  * PgStat_StatDBEntry			The collector's data per database
@@ -746,6 +759,15 @@ typedef struct PgStat_GlobalStats
 } PgStat_GlobalStats;
 
 /*
+ * WAL statistics kept in the stats collector
+ */
+typedef struct PgStat_WalStats
+{
+	PgStat_Counter wal_buffers_full;
+	TimestampTz stat_reset_timestamp;
+} PgStat_WalStats;
+
+/*
  * SLRU statistics kept in the stats collector
  */
 typedef struct PgStat_SLRUStats
@@ -1266,6 +1288,11 @@ extern char *pgstat_stat_filename;
 extern PgStat_MsgBgWriter BgWriterStats;
 
 /*
+ * WAL statistics counter is updated by backends and background processes
+ */
+extern PgStat_MsgWal WalStats;
+
+/*
  * Updated by pgstat_count_buffer_*_time macros
  */
 extern PgStat_Counter pgStatBlockReadTime;
@@ -1464,6 +1491,7 @@ extern void pgstat_twophase_postabort(TransactionId xid, uint16 info,
 
 extern void pgstat_send_archiver(const char *xlog, bool failed);
 extern void pgstat_send_bgwriter(void);
+extern void pgstat_send_wal(void);
 
 /* ----------
  * Support functions for the SQL-callable functions to
@@ -1478,6 +1506,7 @@ extern PgStat_StatFuncEntry *pgstat_fetch_stat_funcentry(Oid funcid);
 extern int	pgstat_fetch_stat_numbackends(void);
 extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
 extern PgStat_GlobalStats *pgstat_fetch_global(void);
+extern PgStat_WalStats *pgstat_fetch_stat_wal(void);
 extern PgStat_SLRUStats *pgstat_fetch_slru(void);
 
 extern void pgstat_count_slru_page_zeroed(int slru_idx);