On Fri, Oct 21, 2011 at 1:40 PM, Florian Pflug <f...@phlo.org> wrote: > AFAIR, the performance hit we'd take by making the vacuum cutoff point > (i.e. GetOldestXmin()) global instead of database-local has been repeatedly > used in the past as an against against cross-database queries. I have to > admit that I currently cannot seem to find an entry in the archives to > back that up, though.
I think the main argument against cross-database queries is that every place in the backend that, for example, uses an OID to identify a table would need to be modified to use a database OID and a table OID. Even if the distributed performance penalty of such a change doesn't bother you, the amount of code churn that it would take to make such a change is mind-boggling. I haven't seen anyone explain why they really need this feature anyway, and I think it's going in the wrong direction. IMHO, anyone who wants to be doing cross-database queries should be using schemas instead, and if that's not workable for some reason, then we should improve the schema implementation until it becomes workable. I think that the target use case for separate databases ought to be multi-tenancy, but what is needed there is actually more isolation (e.g. wrt/role names, cluster-wide visibility of pg_database contents, etc.), not less. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers