Re: postgres external table

Having 'external tables' lets us avoid the step of loading data from a
file into the table. We do not have to check whether a load job has run
successfully, whether the data in the table really corresponds to the data
in the file etc. It also lets us decide how many rejects can be allowed
and so forth.
http://www.adp-gmbh.ch/ora/misc/ext_table.html
Other than that, I have not found any advantage.
Jayadevan

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, Amy Smith
<vah123(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org
Date: 01/18/2010 08:25 PM
Subject: Re: [GENERAL] postgres external table
Sent by: pgsql-general-owner(at)postgresql(dot)org

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?

regards, tom lane

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