Aurora don't have pg_stat_wal information leading to calculation mistakes

[jobinau]

Currently the pg_gather is falling back to pg_stat_wal information for getting the stats_reset if Database level stats reset information is not available.
However AWS Aurora don't provide this information. Which is leading to calculation mistakes at database level and table level.
This Problem is reported by @laudares

[jobinau]

One option is to look for the stats reset information in multiple location and get the oldest of it as a fallback timestamp, if the DB level reset information is missing.

SELECT min(min) AS reset_ts FROM 
(SELECT min(stats_reset) FROM pg_get_io
UNION
SELECT stats_reset FROM pg_stat_archiver
UNION
SELECT stats_reset FROM pg_get_wal
UNION
SELECT stats_reset FROM pg_get_bgwriter) a \gset