[vinayan3]

To add on. If you are joining against a table where you are joining on a UUID the join becomes quite slow with very large tables, like >10 million rows.

PG will say it's doing a hash look up and you'd think it'd be fast but it will take quite sometime relative to joining two large tables with integer IDs. With UUIDS PG will give up doing a hash look up sometimes and try to do table scans unless you adjust random_page_cost.

In general joining on UUIDs for large tables is a bad idea. It can be great if you are joining a single row to another row.