Re: Compression of full-page-writes

On Fri, Jan 2, 2015 at 1:59 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> On Thu, Jan 1, 2015 at 10:40:53AM +0530, Amit Kapila wrote:
> > Good question, I think there might be some impact due to that, but in
> > general for page level compression still there will be much more to
> > compress.
> >
> > In general, I think this idea has merit with respect to compressible
data,
> > and to save for the cases where it will not perform well, there is a
on/off
> > switch for this feature and in future if PostgreSQL has some better
> > compression method, we can consider the same as well. One thing
> > that we need to think is whether user's can decide with ease when to
> > enable this global switch.
>
> Yes, that is the crux of my concern. I am worried about someone who
> assumes compressions == good, and then enables it. If we can't clearly
> know when it is good, it is even harder for users to know.

I think it might have been better if this switch is a relation level switch
as whether the data is compressible or not can be based on schema
and data in individual tables, but I think your concern is genuine.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com