On Tue, Nov 16, 2010 at 3:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Tue, Nov 16, 2010 at 1:58 PM, Alvaro Herrera
>>> I think if you do a regular backup of the complete database, unlogged
>>> tables should come out empty, but if you specifically request a dump of
>>> it, it shouldn't.
>
>> Oh, wow. That seems confusing.
>
> I don't like it either.
>
> I think allowing pg_dump to dump the data in an unlogged table is not
> only reasonable, but essential. Imagine that someone determines that
> his reliability needs will be adequately served by unlogged tables plus
> hourly backups. Now you're going to tell him that that doesn't work
> because pg_dump arbitrarily excludes the data in unlogged tables?
Yeah, you'd have to allow a flag to control the behavior. And in that
case I'd rather the flag have a single default rather than different
defaults depending on whether or not individual tables were selected.
Something like --omit-unlogged-data.
Incidentally, unlogged tables plus hourly backups is not dissimilar to
what some NoSQL products are offering for reliability. Except with
PG, you can (or soon will be able to, hopefully) selectively apply
that lowered degree of reliability to a subset of your data for which
you determine it's appropriate, while maintaining full reliability
guarantees for other data. I am not aware of any other product which
offers that level of fine-grained control over durability.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company