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