[Qgis-developer] Lib_Refactoring-branch update

Martin Dobias wonder.sk at gmail.com
Wed Dec 6 14:47:48 EST 2006

On 12/6/06, Marco Hugentobler <marco.hugentobler at karto.baug.ethz.ch> wrote:
> Am Mittwoch, 6. Dezember 2006 15:06 schrieb Martin Dobias:
> > currently spatial indexing is just a feature that no other part of
> > QGIS uses (so far).  But I have a long-time vision of offering some
> > functionality for provider if it doesn't support that natively:
> > - fast spatial lookup - using spatial indexing
> > - filtering features by attributes - using search strings
> > - fast feature retreiving - by caching of features in memory
> > - maybe also fast attribute searching - using B-trees or similar
> Nice! A fast feature access by id will allow us to have a smarter attribute
> table which fetches attributes when needed.
> Do you have a timeline in mind for those implementations? If you need help, I
> think I could add with coding work.

No, I have no timeline for this - it's been always a just part of the
bigger vision of conquering the world :-) In real we're not far away.
We have backends for spatial indexing and attribute filtering, just we
need to enable them for a provider in a manner that it could be used

Caching features is something I've not thought much about, so any
design ideas or coding would be most welcome. I'd like to see it
flexible, but not too complicated. User-customizable memory amount
(let's say 50 mb by default) could be used to cache the features, and
features can be removed from the cache using "least recently used"

Attribute indexing is not that crucial for now, but it could help in
some cases - e.g. attribute filtering or searcing in attribute table,
maybe in future for joining tables etc.


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