Oracle takes this to its logical extreme by allowing pre-queries that sample some of the data, so it can change the query plan on the fly if it's taking too lon

Oracle takes this to its logical extreme by allowing pre-queries that sample some of the data, so it can change the query plan on the fly if it's taking too long. It's a very powerful feature, but for many workloads it's not worth it. It's worth noting that better statistics and data sampling are usually more important to producing a great plan than exhaustively exploring, e.g., join order (especially for things like many-to-many joins).