Add wal_fpi_bytes to wal_stats metric

internal/metrics/metrics.yaml

@@ -4137,6 +4137,27 @@ metrics:
                     wal_sync_time
                 from
                     pg_stat_wal, io
+            19: |-
+                with io as (
+                  select 
+                    sum(writes) as wal_write, 
+                    sum(fsyncs) as wal_sync,
+                    sum(round(write_time::numeric, 3)::int8) as wal_write_time,
+                    sum(round(fsync_time::numeric, 3)::int8) as wal_sync_time
+                  from pg_stat_io where "object" = 'wal')
+                select /* pgwatch_generated */
+                    (extract(epoch from now()) * 1e9)::int8 as epoch_ns,
+                    wal_records,
+                    wal_fpi,
+                    (wal_bytes / 1024)::int8 as wal_bytes_kb,
+                    wal_fpi_bytes,
+                    wal_buffers_full,
+                    wal_write,
+                    wal_sync,
+                    wal_write_time,
+                    wal_sync_time
+                from
+                    pg_stat_wal, io
     datfrozenxid:
         description: >
             This metric collects information about the database frozen transaction ID.