> PostgreSQL doesn't support specifying which method is used for a particular join
Not directly, no. You can make some of them possible / impossible depending on your indexing and server settings, as well as the query itself. For example, if the smaller side of the join can't fix into `work_mem` – which defaults to 4 MiB – you won't get a hash join. You can either create smaller tables, more restrictive join conditions, or increase the size of `work_mem` (but be careful not to blow up the DB, since that's per connection).
Not directly, no. You can make some of them possible / impossible depending on your indexing and server settings, as well as the query itself. For example, if the smaller side of the join can't fix into `work_mem` – which defaults to 4 MiB – you won't get a hash join. You can either create smaller tables, more restrictive join conditions, or increase the size of `work_mem` (but be careful not to blow up the DB, since that's per connection).