Add metrics for tables

[bazmap]

Proposal

Adding metrics for tables is important as it allows you to monitor what causes troubles into your database.

You can use this query to have informations over your tables :
Adding the result of this query into the metrics collected :

SELECT 
	pg_stat.*,
	pg_statio.*,
	pgc.*,
	pg_relation_size(pgc.oid)
FROM pg_catalog.pg_stat_user_tables AS pg_stat 
LEFT JOIN pg_catalog.pg_statio_user_tables AS pg_statio
	ON pg_statio.relid = pg_stat.relid
LEFT JOIN pg_catalog.pg_class AS pgc 
	ON pgc.oid = pg_stat.relid
;

Why ?

Because you can tracks each table into the database wich helps you to monitor what table can cause trouble.
Some examples :

• seq_scan over seq_tup_read allows you to know if you need index
• Which table haven't been autovacuumed.
• The size of each relations (aka table) : size, nb of tuples, nb of pages
• Number of deadrows

This need to be desactivated as this request return as many line as the number of table into the database.

[bazmap]

Ok I think thats because the pg_stat_user_tables and the pg_statio_user_tables is not activated by default... (the doc says that this is activated by default...)
I will give it a try and closed this issue or change what I need.
Sorry

[bazmap]

Ok these metrics are implemented but the last postgres_exporter doesn't show these on PostgreSQL 11 - Windows 11.
I check other tests and will give you more details

[bazmap]

Ok I found the trouble : I was connected to the "postgres" database which doesn't contain anything... If I specify another databse in the same instance, I have my statistics.
The documentation should indicate that the data collected are only for one database and not for the whole instance.
This is more or less link to the #999 issue.
I will close this one but keep this explaination for other people.