Added to TODO:
* Research storing disk pages with no alignment/padding
---------------------------------------------------------------------------
Lincoln Yeoh wrote:
> I believe that one should leave such on-the-fly disk compression to the
> O/S. Postgresql already does compression for TOAST.
>
> However, maybe padding for alignment is a waste on the disk - disks being
> so much slower than CPUs (not sure about that once the data is in memory ).
> Maybe there should be an option to reorder columns so that less space is
> wasted.
>
> At 05:47 PM 7/17/2005 -0500, Jim C. Nasby wrote:
>
> >On Sat, Jul 16, 2005 at 03:18:24PM -0700, Ron Mayer wrote:
> >
> > > If that were practical, even more radical I/O saving tricks might be
> > > possible beyond removing alignment bytes - like some compression algorithm.
> >
> >True, though there's a few issues with zlib compression. First, you have
> >to be able to pull specific pages out of the files on disk. Right now
> >that's trivial; you just read bytes xxx - yyy. With compression things
> >are more difficult, because you no longer have a fixed page size.
> >
> >methods. Another factor is that more complex compression methods will be
> >much more CPU intensive.
> >
> >FWIW, the way oracle handles compression is as a one-time operation.
> >When you tell it to compress a table it will re-write the entire table,
> >compressing it as it goes. But any pages that get changed after that
> >will end up uncompressed. Of course in a data warehouse environment
> >that's perfectly acceptable.
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
