Re: postgres external table - Mailing list pgsql-general
Yes. We get quite a few files as 'feeds' from external systems. Once the files are in our network, we know that no changes will happen to those files. We access them using Oracle external tables and process them (the data, after some processing, end up in other real tables). If external tables were not there, we would have had to schedule some job to load these files.
Jayadevan
From: Greg Stark <gsstark@mit.edu>
To: Craig Ringer <craig@postnewspapers.com.au>
Cc: Vincenzo Romano <vincenzo.romano@notorand.it>, Tom Lane <tgl@sss.pgh.pa.us>, Greg Smith <greg@2ndquadrant.com>, Amy Smith <vah123@gmail.com>, pgsql-general@postgresql.org
Date: 01/19/2010 04:37 PM
Subject: Re: [GENERAL] postgres external table
Sent by: pgsql-general-owner@postgresql.org
On Tue, Jan 19, 2010 at 4:41 AM, Craig Ringer
<craig@postnewspapers.com.au> wrote:
> How can that work without a transactional file system, though? If the
> external process writes to the file while you're half-way through reading
> it, what's the database to do? In general, how do external tables cope with
> the fact that they're on non-transactional storage?
Well if you use mv to replace the old file with the new one then it
should be safe. Unless your query involves opening the table multiple
times or your transactions are more complex than a single query...
--
greg
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Jayadevan
From: Greg Stark <gsstark@mit.edu>
To: Craig Ringer <craig@postnewspapers.com.au>
Cc: Vincenzo Romano <vincenzo.romano@notorand.it>, Tom Lane <tgl@sss.pgh.pa.us>, Greg Smith <greg@2ndquadrant.com>, Amy Smith <vah123@gmail.com>, pgsql-general@postgresql.org
Date: 01/19/2010 04:37 PM
Subject: Re: [GENERAL] postgres external table
Sent by: pgsql-general-owner@postgresql.org
On Tue, Jan 19, 2010 at 4:41 AM, Craig Ringer
<craig@postnewspapers.com.au> wrote:
> How can that work without a transactional file system, though? If the
> external process writes to the file while you're half-way through reading
> it, what's the database to do? In general, how do external tables cope with
> the fact that they're on non-transactional storage?
Well if you use mv to replace the old file with the new one then it
should be safe. Unless your query involves opening the table multiple
times or your transactions are more complex than a single query...
--
greg
--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
DISCLAIMER:
"The information in this e-mail and any attachment is intended only for the person to whom it is addressed and may contain confidential and/or privileged material. If you have received this e-mail in error, kindly contact the sender and destroy all copies of the original communication. IBS makes no warranty, express or implied, nor guarantees the accuracy, adequacy or completeness of the information contained in this email or any attachment and is not liable for any errors, defects, omissions, viruses or for resultant loss or damage, if any, direct or indirect."
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