[GRASS-dev] vector libs: file based spatial index

[Markus Metz]

Martin Landa wrote:
> Hi Markus,
>
> 2009/7/7 Markus Metz <markus.metz.giswork at googlemail.com>:
>
> [...]
>
>   
>> For the time being, the only reasonable way to deal with these massive
>> datasets is to *not* build topology. It's not not only the spatial index
>> that is getting out of hand, also topology itself and the category
>> index. The grass vector libs must be told that there is nothing special
>> about point datasets (to cite Hamish) which means rewriting major parts
>> of the vector libs, and that takes time.
>>     
>
> BTW, are you planning to commit your changes in sidx to trunk?
>   
Yes, after I'm done with testing. I have the probably unrealistic aim to
get building the new file-based spatial index as fast as the current
memory-based index, and I still have to implement the new memory-based
version, currently it's all file-based. I have polished the file-based
version with R*-tree methods and speed optimizations (amongst others a
custom quicksort), but adjusting the grass vector libs to use either the
memory-based version or the file-based version is really a lot of work.
It will take me at least another week to get it right, e.g. decide what
tasks should be done by Vlib and what tasks should be done by diglib,
and how the two should work together. I can send you a detailed
technical report if you want, but I'm afraid it will be very technical
and potentially boring unless you are interested in performance
differences between Toni Guttmann's RTree and Norbert Beckmann's
R*-tree. I would need some help to get random file access optimized,
it's not too bad in my tests but I don't know if it can get better.

Markus M