On Tue, Oct 22, 2013 at 2:00 AM, Dimitri Fontaine <dimi...@2ndquadrant.fr>wrote:
> Tom Lane <t...@sss.pgh.pa.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.
