On Fri, Mar 26, 2021, at 14:16, Tom Lane wrote: > Alvaro Herrera <alvhe...@alvh.no-ip.org <mailto:alvherre%40alvh.no-ip.org>> > writes: > > On 2021-Mar-26, Joel Jacobson wrote: > >> On Thu, Mar 25, 2021, at 17:51, Tom Lane wrote: > >> I wonder what performance will be like with lots o' objects. > > > I guess he is concerned about the number of catalog accesses. > > My concern is basically that you're forcing the join between > pg_shdepend and $everything_else to be done as a nested loop. > It will work well, up to where you have so many objects that > it doesn't ... but the planner will have no way to improve it.
Thanks Alvaro and Tom for explaining. > Having said that, I don't really see a better way either. > Materializing $everything_else via a UNION ALL seems like > no fun from a maintenance perspective, plus we're not that > great on optimizing such constructs either. I see why pg_shdepend+pg_get_acl() is to prefer. That said, I think maintenance of UNION ALL would actually not be too bad, since the system views could initially be generated by a query using information_schema, and the same query could update them when new catalogs are added. /Joel
