Re: [HACKERS] Cube extension point support // GSoC'13

On Tue, Oct 22, 2013 at 2:00 AM, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>wrote:

> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> > I believe the reason GIST has compress/decompress functions is not for
> > TOAST (they predate that, if memory serves), but to allow the on-disk
> > representation of an index entry to be different from the data type's
> > normal representation in other ways --- think lossy storage in
> particular.
>
> My understanding of the use case for those functions is to do with
> storing a different data type in the index upper nodes and in the index
> leafs. It should be possible to do that in a non-lossy way, so that you
> would implement compress/decompress and not declare the RECHECK bits.
>
> Then again I'm talking from 8.3 era memories of when I tried to
> understand GiST enough to code the prefix extension.

Actually, I mean purpose of this particular decompress function
implementation, not compress/decompress in general. I understand that in
general compress/decompress can do useful job.

------
With best regards,
Alexander Korotkov.