From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | bruc(at)acm(dot)org |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Are we losing momentum? |
Date: | 2003-04-15 23:18:24 |
Message-ID: | 10857.1050448704@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
"Robert E. Bruccoleri" <bruc(at)stone(dot)congenomics(dot)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
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