[mnw21cam]

I might be out of touch a little with Postgres (I last used it in 2010), but my impression was that COUNT(*) still needed to scan the actual table in order to exclude rows that had been deleted in a transaction, due to the way multi-version concurrency worked. Is this something that has been improved since then?

[zeroimpl]

They support index-only scans now, so there is some sort of optimization which bypasses the table lookup, at least in certain cases.