Re: postgres external table

On Mon, Jan 18, 2010 at 7:57 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Greg Smith <greg(at)2ndquadrant(dot)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.