Remove read/sync fields from pg_stat_wal and GUC track_wal_io_timing

The four following attributes are removed from pg_stat_wal:
* wal_write
* wal_sync
* wal_write_time
* wal_sync_time

a051e71e28a1 has added an equivalent of this information in pg_stat_io
with more granularity as this now spreads across the backend types, IO
context and IO objects.  So, keeping the same information in pg_stat_wal
has little benefits.

Another benefit of this commit is the removal of PendingWalStats,
simplifying an upcoming patch to add per-backend WAL statistics, which
already support IO statistics and which have access to the write/sync
stats data of WAL.

The GUC track_wal_io_timing, that was used to enable or disable the
aggregation of the write and sync timings for WAL, is also removed.
pgstat_prepare_io_time() is simplified.

Bump catalog version.
Bump PGSTAT_FILE_FORMAT_ID, due to the update of PgStat_WalStats.

Author: Bertrand Drouvot <[email protected]>
Discussion: https://postgr.es/m/Z7RkQ0EfYaqqjgz/@ip-10-97-1-34.eu-west-3.compute.internal

1 files changed, 2 insertions, 22 deletions

diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c
index c1ca65eb991..4dc41a4a590 100644
--- a/src/backend/utils/activity/pgstat_wal.c
+++ b/src/backend/utils/activity/pgstat_wal.c
@@ -21,8 +21,6 @@
 #include "utils/pgstat_internal.h"
 
 
-PgStat_PendingWalStats PendingWalStats = {0};
-
 /*
  * WAL usage counters saved from pgWalUsage at the previous call to
  * pgstat_report_wal(). This is used to calculate how much WAL usage
@@ -118,17 +116,10 @@ pgstat_wal_flush_cb(bool nowait)
 
 #define WALSTAT_ACC(fld, var_to_add) \
 	(stats_shmem->stats.fld += var_to_add.fld)
-#define WALSTAT_ACC_INSTR_TIME(fld) \
-	(stats_shmem->stats.fld += INSTR_TIME_GET_MICROSEC(PendingWalStats.fld))
 	WALSTAT_ACC(wal_records, wal_usage_diff);
 	WALSTAT_ACC(wal_fpi, wal_usage_diff);
 	WALSTAT_ACC(wal_bytes, wal_usage_diff);
 	WALSTAT_ACC(wal_buffers_full, wal_usage_diff);
-	WALSTAT_ACC(wal_write, PendingWalStats);
-	WALSTAT_ACC(wal_sync, PendingWalStats);
-	WALSTAT_ACC_INSTR_TIME(wal_write_time);
-	WALSTAT_ACC_INSTR_TIME(wal_sync_time);
-#undef WALSTAT_ACC_INSTR_TIME
 #undef WALSTAT_ACC
 
 	LWLockRelease(&stats_shmem->lock);
@@ -138,11 +129,6 @@ pgstat_wal_flush_cb(bool nowait)
 	 */
 	prevWalUsage = pgWalUsage;
 
-	/*
-	 * Clear out the statistics buffer, so it can be re-used.
-	 */
-	MemSet(&PendingWalStats, 0, sizeof(PendingWalStats));
-
 	return false;
 }
 
@@ -158,18 +144,12 @@ pgstat_wal_init_backend_cb(void)
 }
 
 /*
- * To determine whether any WAL activity has occurred since last time, not
- * only the number of generated WAL records but also the numbers of WAL
- * writes and syncs need to be checked. Because even transaction that
- * generates no WAL records can write or sync WAL data when flushing the
- * data pages.
+ * To determine whether WAL usage happened.
  */
 bool
 pgstat_wal_have_pending_cb(void)
 {
-	return pgWalUsage.wal_records != prevWalUsage.wal_records ||
-		PendingWalStats.wal_write != 0 ||
-		PendingWalStats.wal_sync != 0;
+	return pgWalUsage.wal_records != prevWalUsage.wal_records;
 }
 
 void