On Mon, Jan 18, 2010 at 7:57 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Greg Smith <greg@2ndquadrant.com> writes:
>> Craig Ringer wrote:
>>> For those non-Oracle users among us, what's an external table?
>
>> External tables let you map a text file directly to a table without
>> explicitly loading it. In PostgreSQL, if you have data in a CSV file,
>> usually you'd import it with COPY before you'd use it. If external
>> tables were available, you'd just say there's an external table as a CSV
>> file and you could start running queries against it.
>
> I'm finding it hard to visualize a use-case for that. We must postulate
> that the table is so big that you don't want to import it, and yet you
> don't feel a need to have any index on it. Which among other things
> implies that every query will seqscan the whole table. Where's the
> savings?
I've used it mostly for importing in the past. Saves the step of
loading a large file into a table with no constraints as a middle
step.
