On 09/13/2011 03:51 PM, Michael Nolan wrote:
For example:
A fully integrated ability to query across multiple
databases,possibly
on multiple servers, something Oracle has had for nearly two
decades.
That isn't the approach to take. The fact that Oracle has it is
not a guarantee that it is useful or good. If you need to query
across databases (assuming within the same cluster) then you
designed your database wrong and should have used our SCHEMA
support (what Oracle calls Namespaces) instead.
This is the difference between developers and real world users. Real
world users may not have the ability, time or resources to redesign
their databases just because that's the 'best' way to do something.
Will it be the most efficient way to do it? Almost certainly not.
I've been involved in a few corporate mergers, and there was a short
term need to do queries on the combined databases while the tiger team
handling the IT restructuring figured out how (or whether) to merge
the dabases together. (One of these happened to be an Oracle/Oracle
situation, it was a piece of cake even though the two data centers
were 750 miles apart and the table structures had almost nothing in
common. Another was a two week headache, the third was even worse!)
In a perfect world, it would be nice if one could do combined queries
linking a PostgreSQL database with an Oracle one, or a MySQL one,
too. Because sometimes, that's what you gotta do. Even something
that is several hundred times slower is going to be faster than
merging the databases together. When I do this today, I have to write
a program (in perl or php) that accesses both databases and merges it
by hand.
Can't you do that with FDW that is present in 9.1?
Check http://wiki.postgresql.org/wiki/Foreign_data_wrappers
