Re: WIP: SP-GiST, Space-Partitioned GiST

We are working on the hackers documentation, hope to submit it before my
himalaya track.

Oleg
On Sun, 2 Oct 2011, Tom Lane wrote:

> Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
>> On 06.09.2011 20:34, Oleg Bartunov wrote:
>>> Here is the latest spgist patch, which has all planned features as well as
>>> all overhead, introduced by concurrency and recovery, so performance
>>> measurement should be realistic now.
>
>> I'm ignoring the text suffix-tree part of this for now, because of the
>> issue with non-C locales that Alexander pointer out.
>
> It seems to me that SP-GiST simply cannot work for full text comparisons
> in non-C locales, because it's critically dependent on the assumption
> that comparisons of strings are consistent with comparisons of prefixes
> of those strings ... an assumption that's just plain false for most
> non-C locales.
>
> We can dodge that problem in the same way that we did in the btree
> pattern_ops opclasses, namely implement the opclass only for the =
> operator and the special operators ~<~ etc.  I think I favor doing this
> for the first round, because it's a simple matter of removing code
> that's currently present in the patch.  Even with only = support
> the opclass would be extremely useful.
>
> Something we could consider later is a way to use the index for the
> regular text comparison operators (< etc), but only when the operator
> is using C collation.  This is not so much a matter for the index
> implementation as it is about teaching the planner to optionally
> consider collation when matching an operator call to the index.  It's
> probably going to tie into the unfinished business of marking which
> operators are collation sensitive and which are not.
>
> In other news, I looked at the patch briefly, but I don't think I want
> to review it fully without some documentation.  The absolute minimum
> requirement IMO is documentation comparable to what we have for GIN,
> ie a specification for the support methods and some indication of when
> you'd use this index type in preference to others.  I'd be willing to
> help copy-edit and SGML-ize such documentation, but I do not care to
> reverse-engineer it from the code.
>
> 			regards, tom lane
>

 	Regards,
 		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83