Has anyone put any thought or effort into figuring out how to measure the total volume of data in a database against how much of it is hot? I'm looking for some automatable approaches. Similarly, is there a way to measure rarely queried columns, or unused functions & triggers?
pg_stat_user_tables tells you how many records have been inserted, updated and deleted since the instance was started. It does not, though, say which records were updated,
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For monitoring data itself, I'm not sure of anything else built in other than what Ron shared with the stats table. If this is something you really need to monitor, perhaps look into adding a "changed_at" column to the tables that really need it and set a trigger to automatically update the timestamp of that column whenever the row is updated. Not sure how to track column usage.
