[postgis-users] implement your own index

[Biddy]

Mark,

many thanks for all these very useful pointers.

B.

Zitat von Mark Cave-Ayland <mark.cave-ayland at siriusit.co.uk>:

> Biddy wrote:
>
>> María, thank you for the fast reply. However, these docs refer to  
>> the usage of GIST.
>>
>> If I understand it correctly, an R-tree is implemented on top of GIST.
>> What if I don't want to use an R-tree? If I wanted to implement my  
>> own ...let's say I want to implement a quadtree or some other new,  
>> fancy index. How would I go about doing it?
>
> The GIST API currently does not support space partition-based nor  
> ordered indices (see  
> http://www.postgresql.org/docs/8.4/interactive/gist-implementation.html for  
> the exact details). So if you wanted to implement a quadtree or  
> nearest neighbour type index searches then you'd need to alter the  
> GIST API or invent another index AM in PostgreSQL first.
>
> You may find the SP-GIST project interesting in this respect:  
> http://www.cs.purdue.edu/spgist/.
>
>> Additionally, is there a way to change the attributes with which  
>> the R-tree is built? Or at least see how the R-tree is built?
>
> It depends what attributes you are trying to modify. If they can be  
> defined in terms of the GIST picksplit function then it is likely  
> possible.
>
> In terms of visualising the R-Tree itself, Oleg and Teodor's gevel  
> module from http://www.sai.msu.su/~megera/postgres/gist/ can be used  
> as an aid to generate output suitable for rendering.
>
>
> HTH,
>
> Mark.
>
> -- 
> Mark Cave-Ayland - Senior Technical Architect
> PostgreSQL - PostGIS
> Sirius Corporation plc - control through freedom
> http://www.siriusit.co.uk
> t: +44 870 608 0063
>
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