4 ms·
That would highly depend on what you select. If the query could be answered by index only, like COUNT(*), it would probably use the index. You are right if you
by maweki 6y ago
That would highly depend on what you select. If the query could be answered by index only, like COUNT(*), it would probably use the index. You are right if you want to query any data from that row that's not in the index.
- mnw21cam 6y agoI 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 6y agoThey support index-only scans now, so there is some sort of optimization which bypasses the table lookup, at least in certain cases.