Hi, On 2021-06-17 14:22:52 -0400, Robert Haas wrote: > On Thu, Jun 17, 2021 at 2:17 PM Andres Freund <and...@anarazel.de> wrote: > > Adding a hacky special case implementation for cross-database relation > > accesses that violates all kinds of assumptions (like holding a lock on > > a relation when accessing it / pinning pages, processing relcache > > invals, ...) doesn't seem like a good plan. > > I agree that we don't want hacky code that violates assumptions, but > bypassing shared_buffers is a bit hacky, too. Can't we lock the > relations as we're copying them? We know pg_class's OID a fortiori, > and we can find out all the other OIDs as we go.
We possibly can - but I'm not sure that won't end up violating some other assumptions. > I'm just thinking that the hackiness of going around shared_buffers > feels irreducible, but maybe the hackiness in the patch is something > that can be solved with more engineering. Which bypassing of shared buffers are you talking about here? We'd still have to solve a subset of the issues around locking (at least on the source side), but I don't think we need to read pg_class contents to be able to go through shared_buffers? As I suggested, we can use the init fork presence to infer relpersistence? Or do you mean that looking at the filesystem at all is bypassing shared buffers? Greetings, Andres Freund
