[postgis-devel] [cartodb] Re: GSOC weekly report 2 : Spatial clustering in PostGIS and CartoDB

[mohit kumar]

Hi,
The idea to index was to get the points faster and clustered.
And I didn't got what you meant by your question.
Without indexing it could work but then processing needs to be done as a
controller not on a dB level. Or by changing the whole dB in a quad tree
format, which we are trying to implement by indexing the database.

Regards,
Mohit
On Jun 10, 2014 12:03 AM, "Oleg Bartunov" <obartunov at gmail.com> wrote:
>
> One quick question.  Are you mind  it should works without index !
>
> On Sat, Jun 7, 2014 at 6:25 AM, mohit kumar <mohitkharb at gmail.com> wrote:
> > Thanks Oleg for the help.
> > I am looking at the examples of the spgist opclasses, and would get
back to
> > you in case of any doubt.
> > My idea for clustering was to index point data using quad trees and
display
> > a single point in place of cluster of spatially close points.
> > The zoom level will decide the spatially close points that can be
> > represented as a single point. This zoom level would be given by the
> > map(user). If this value is integrated in indexing, the nodes having the
> > zoom value lower than the asked value would be send by the dB to the
map.
> > The purpose of keeping the child nodes was to show the number of points
in
> > the cluster represented by the single point. This point will be that
node
> > whose zoom value equaling the zoom value of the map.
> > I know this will make index creation very slow, but once done, the point
> > display in the map might become a lot cleaner.
> > This was what I thought on implementation of the work.
> > Your feedback and suggestions are much needed.
> >
> > Regards,
> > Mohit
> >
> > On Jun 6, 2014 4:45 PM, "Oleg Bartunov" <obartunov at gmail.com> wrote:
> >>
> >> Mohit,
> >>
> >> could you explain us what do you want from us :)
> >> Basically, you need to create new type (if needed) and write opclass
for
> >> spgist.  There are several questions:
> >>
> >> 1. Where do you get zoom level ?
> >> 2. Are you sure you want to keep number of child nodes ? It's too slow
for
> >> index creation.
> >>
> >> you may look  examples of spgist opclasses
> >> src/backend/access/spgist
> >>
> >>  Oleg
> >> On Jun 5, 2014 12:50 PM, "mohit kumar" <mohitkharb at gmail.com> wrote:
> >>>
> >>> Thanks Strk for the help.
> >>> I have now moved to postgresSQL implementation of the sp-gist indexing
> >>> and am working on it.
> >>>
> >>> Hi Teodor,Oleg, actually along with the sp-gist index in  PostGIS
> >>> Geometry (point data) I wanted to store the zoom levels and number of
child
> >>> nodes along the indexes for a better indexing at a given zoom level.
> >>>
> >>> Regards,
> >>> Mohit
> >>>
> >>>
> >>> On Wed, Jun 4, 2014 at 3:00 PM, Sandro Santilli <strk at keybit.net>
wrote:
> >>>>
> >>>> [moved exclusively to postgis-devel]
> >>>>
> >>>> On Wed, Jun 04, 2014 at 12:29:56AM +0530, mohit kumar wrote:
> >>>> > On Tue, Jun 3, 2014 at 5:20 PM, Sandro Santilli <strk at cartodb.com>
> >>>> > wrote:
> >>>>
> >>>> > > What's in that package that isn't already in the PostgreSQL
> >>>> > > SP-GiST index ?
> >>>> > > http://www.postgresql.org/docs/9.2/static/spgist.html
> >>>> > >
> >>>> > > I mean, don't you only need to implement the PostGIS connector ?
> >>>> >
> >>>> > I wanted to modify the code for sp-gist to inculcate another
integer
> >>>> > field
> >>>> > for various levels of clustering, so worked on the source code by
> >>>> > purdue
> >>>> > research group.
> >>>>
> >>>> The best would be to contribute a patch back to PostgreSQL to make
the
> >>>> existing sp-gist code capable of doing what you need, if it isn't
> >>>> already.
> >>>>
> >>>> I've added Teodor and Oleg (authors of the PostgreSQL implmentation)
in
> >>>> Cc,
> >>>> could you describe what your additional integer is meant to provide ?
> >>>>
> >>>> Teodor, Oleg, the context here is adding sp-gist support to PostGIS
> >>>> Geometry
> >>>> and using those indices to quickly compute population in a quadtree
> >>>> tile.
> >>>>
> >>>> REF:
> >>>>
> >>>>
http://www.google-melange.com/gsoc/proposal/public/google/gsoc2014/mohitkharb/5698390809640960
> >>>>
> >>>> --strk;
> >>>>
> >>>>  ()  ASCII ribbon campaign  --  Keep it simple !
> >>>>  /\  http://strk.keybit.net/rants/ascii_mails.txt
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> Mohit Kumar
> >>> +91-970-3840-175
> >>> Lab For Spatial Informatics
> >>> International Institute of Information Technology
> >>> Hyderabad, India
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