[-] remove pg_stat_file() dependencies from metrics (#677)

Author: pashagolub

internal/metrics/metrics.yaml

@@ -410,9 +410,6 @@ metrics:
             - '*'
         metric_storage_name: db_size
     db_stats:
-        init_sql: |-
-            GRANT EXECUTE ON FUNCTION pg_stat_file(text) TO pgwatch;
-            GRANT EXECUTE ON FUNCTION pg_stat_file(text, boolean) TO pgwatch;
         sqls:
             11: |-
                 select /* pgwatch_generated */
@@ -433,7 +430,7 @@ metrics:
                   deadlocks,
                   blk_read_time,
                   blk_write_time,
-                  extract(epoch from (now() - coalesce((pg_stat_file('postmaster.pid', true)).modification, pg_postmaster_start_time())))::int8 as postmaster_uptime_s,
+                  extract(epoch from (now() - pg_postmaster_start_time()))::int8 as postmaster_uptime_s,
                   extract(epoch from (now() - pg_backup_start_time()))::int8 as backup_duration_s,
                   case when pg_is_in_recovery() then 1 else 0 end as in_recovery_int,
                   system_identifier::text as tag_sys_id,
@@ -469,7 +466,7 @@ metrics:
                   deadlocks,
                   blk_read_time,
                   blk_write_time,
-                  extract(epoch from (now() - coalesce((pg_stat_file('postmaster.pid', true)).modification, pg_postmaster_start_time())))::int8 as postmaster_uptime_s,
+                  extract(epoch from (now() - pg_postmaster_start_time()))::int8 as postmaster_uptime_s,
                   extract(epoch from (now() - pg_backup_start_time()))::int8 as backup_duration_s,
                   checksum_failures,
                   extract(epoch from (now() - checksum_last_failure))::int8 as checksum_last_failure_s,
@@ -507,7 +504,7 @@ metrics:
                   deadlocks,
                   blk_read_time,
                   blk_write_time,
-                  extract(epoch from (now() - coalesce((pg_stat_file('postmaster.pid', true)).modification, pg_postmaster_start_time())))::int8 as postmaster_uptime_s,
+                  extract(epoch from (now() - pg_postmaster_start_time()))::int8 as postmaster_uptime_s,
                   extract(epoch from (now() - pg_backup_start_time()))::int8 as backup_duration_s,
                   checksum_failures,
                   extract(epoch from (now() - checksum_last_failure))::int8 as checksum_last_failure_s,
@@ -552,7 +549,7 @@ metrics:
                   deadlocks,
                   blk_read_time,
                   blk_write_time,
-                  extract(epoch from (now() - coalesce((pg_stat_file('postmaster.pid', true)).modification, pg_postmaster_start_time())))::int8 as postmaster_uptime_s,
+                  extract(epoch from (now() - pg_postmaster_start_time()))::int8 as postmaster_uptime_s,
                   checksum_failures,
                   extract(epoch from (now() - checksum_last_failure))::int8 as checksum_last_failure_s,
                   case when pg_is_in_recovery() then 1 else 0 end as in_recovery_int,
@@ -3930,7 +3927,7 @@ metrics:
                       pg_wal_lsn_diff(pg_last_wal_replay_lsn(), '0/0')::int8
                     end as xlog_location_b,
                   case when pg_is_in_recovery() then 1 else 0 end as in_recovery_int,
-                  extract(epoch from (now() - coalesce((pg_stat_file('postmaster.pid', true)).modification, pg_postmaster_start_time())))::int8 as postmaster_uptime_s,
+                  extract(epoch from (now() - pg_postmaster_start_time()))::int8 as postmaster_uptime_s,
                   system_identifier::text as tag_sys_id,
                   case
                     when pg_is_in_recovery() = false then
@@ -3956,12 +3953,9 @@ metrics:
     wal_size:
         sqls:
             11: |-
-                /* If using not a real superuser but a role with "pg_monitor" grant then below execute grant is needed:
-                  GRANT EXECUTE ON FUNCTION pg_stat_file(text) to pgwatch;
-                */
                 select /* pgwatch_generated */
                     (extract(epoch from now()) * 1e9)::int8 as epoch_ns,
-                    (sum((pg_stat_file('pg_wal/' || name)).size))::int8 as wal_size_b
+                    sum(size)::int8 as wal_size_b
                 from pg_ls_waldir()
         gauges:
             - '*'