"Robert E. Bruccoleri" <bruc@stone.congenomics.com> writes:
> I beg to differ with Tom Lane's opinion, but schemas do not solve the
> problem with multi-database queries because of the following reasons:
> 1) When dealing with large databases, the use of multiple databases
> reduces the risk of wiping out all the data, and reduces the recovery
> time in case of accidents.
> 2) Multiple databases allow for different management policies on each
> database, whereas schemas require some consistency across them all.
> In a heterogeneous working environment, this is a signficant issue.
> 3) PostgreSQL should strive for heterogeneous multi-database queries,
> so that applications currently using other systems could be slowly
> migrated to PostgreSQL by moving portions of a database from other
> vendors to PostgreSQL. In my work, the lack of PostgreSQL - Oracle
> connectivity is a disabling impediment to wider PostgreSQL usage.
Please keep in mind that I was replying to a poster who said "cross-db
queries on the same server (meaning same postmaster, for our purposes)
are trivial; why hasn't Postgres got them when everybody else does?"
Your above arguments are all good ones, but they presume a scenario that
is much different and *MUCH* harder to implement than local "cross
database" queries. My point is that schemas solve the same-server
problems that the original poster was interested in. I did not say,
nor mean, that there is no need for cross-server queries. But that is
a different problem. Today we can only offer dblink; maybe someday
SQL-MED.
regards, tom lane
