Use atomic write for updating WAL statistic

Author: knizhnik

src/backend/access/transam/xlog.c

@@ -1487,7 +1487,7 @@ CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,
 	freespace = INSERT_FREESPACE(CurrPos);
 
 	/* Accumulate amount of data written to WAL for pg_xact_activity */
-	MyProc->walWritten += write_len;
+	pg_atomic_write_u64(&MyProc->walWritten, pg_atomic_read_u64(&MyProc->walWritten) + write_len);
 
 	/*
 	 * there should be enough space for at least the first field (xl_tot_len)

src/backend/storage/lmgr/proc.c

@@ -390,7 +390,7 @@ InitProcess(void)
 	MyPgXact->xid = InvalidTransactionId;
 	MyPgXact->xmin = InvalidTransactionId;
 	MyProc->pid = MyProcPid;
-	MyProc->walWritten = 0;
+	pg_atomic_init_u64(&MyProc->walWritten, 0);
 
 	/* backendId, databaseId and roleId will be filled in later */
 	MyProc->backendId = InvalidBackendId;

src/backend/utils/adt/pgstatfuncs.c

@@ -546,8 +546,7 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_activity(PG_FUNCTION_ARGS)
 {
-
-	#define PG_STAT_GET_ACTIVITY_COLS	29
+#define PG_STAT_GET_ACTIVITY_COLS	29
 	int			num_backends = pgstat_fetch_stat_numbackends();
 	int			curr_backend;
 	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
@@ -931,7 +930,7 @@ pg_stat_get_wal_activity(PG_FUNCTION_ARGS)
 	if (proc == NULL)
 		PG_RETURN_NULL();
 	else
-		PG_RETURN_INT64(proc->walWritten);
+		PG_RETURN_INT64(pg_atomic_read_u64(&proc->walWritten));
 }
 
 

src/include/storage/proc.h

@@ -207,7 +207,7 @@ struct PGPROC
 	/*
 	 * Amount of data written to the WAL by this process
 	 */
-	uint64      walWritten;
+	pg_atomic_uint64 walWritten;
 };
 
 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */