How can querying for PK's than doing a second query on the FK be faster than a join that's semantically equivalent? Postgres optimizer gone terribly wrong or something? Or am I misunderstanding what's going on?
It would never have occurred to me to even try this, I would have assumed postgres would do as well as could be done at what looks like a very standard join. So I guess that's a lesson not to make assumptions?
Not sure, without even having a theory of why pg would behave this way, I'd be worried that as the data changes it might regress again. Or if the phase of the moon changes or something -- since it seems like magic!
It would never have occurred to me to even try this, I would have assumed postgres would do as well as could be done at what looks like a very standard join. So I guess that's a lesson not to make assumptions?
Not sure, without even having a theory of why pg would behave this way, I'd be worried that as the data changes it might regress again. Or if the phase of the moon changes or something -- since it seems like magic!