If this would be accepted I might actually be able to accomplish this.
Maybe. :) But having a TODO wouldn't be a bad idea as well...
Would this require 2 new fields in pg_attribute, or is there a better
way to store the thresholds? I'm thinking that each field would need two
special values; 0 for 'no external/compression' and -1 for 'use default'
(hrm, I guess this means we should add at least one GUC to control that
default...)
I suspect there's folks on -general who would express interest if you
want me to ask there...
On Thu, Mar 02, 2006 at 10:15:19PM -0500, Bruce Momjian wrote:
>
> Is there still interst in this idea for TODO?
>
> ---------------------------------------------------------------------------
> > As Tom suggested, I think it would be best to be able to change the size
> > at which a field gets stored externally. I think it also makes sense to
> > have this reverse the normal order of compress first, then if it still
> > doesn't fit store it externally. I forsee this typically being useful
> > when you have fields that are between ~100 and 1000 bytes in size, and
> > I'm doubtful that compression would do much good there. But I wouldn't
> > rule out this being useful on fields that can also sometimes contain
> > much larger amounts of data, so I don't think it makes sense to disable
> > compression completely. So, I think this leaves two new options:
> >
> > SET STORAGE EXTERNAL [THRESHOLD x]
> > If a field is over x in size, it's stored externally.
> >
> > SET STORAGE EXTENDED [THRESHOLD x]
> > If a field is over x in size, it's stored externally. If it's over
> > BLCKSZ/4 it will also be compressed (I think that's how things work
> > now).
> >
> > Actually, that's rather ugly. I think it would be better to just break
> > external storage and compression out into their own attributes:
> >
> > SET STORAGE [ ALLOW EXTERNAL [THRESHOLD x] ] [ ALLOW COMPRESSION [THRESHOLD x] ]
> >
> > ALLOW EXTERNAL: if a field is larger than x bytes (BLCKSZ/4 by default)
> > then it will be stored externally. May be specified along with ALLOW
> > COMPRESSION.
> >
> > ALLOW COMPRESSION: if a field is larger than x bytes (BLCKSZ/4 by default)
> > then it will be COMPRESSED. May be specified along with ALLOW EXTERNAL.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461