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From Volker Mische <volker.mis...@gmail.com>
Subject Re: using couchdb for 100GB geodata from openstreetmap
Date Sun, 22 Mar 2009 22:54:48 GMT
pablo platt wrote:
> On Mon, Mar 23, 2009 at 12:32 AM, Volker Mische <volker.mische@gmail.com>wrote:
> 
>> Hi,
>>
>> I'll only reply to the GeoCouch bit:
>>
>>> I've read about geocouch -
>>>
>> http://vmx.cx/cgi-bin/blog/index.cgi/geocouch-geospatial-queries-with-couchdb:2008-10-26:en,CouchDB,Python,geo
>>> and my question is if a geo aware couchdb can be built without any python
>>> and SpatiaLite code?
>>>
>>> If I want to be able to make proximity searches - find banks in 3km range
>>> from st some-street
>>> do I need to create some kind of index docs for the views?
>> The problem is that proximity searches are kind of dynamic. CouchDB
>> views are like precomputed result-sets, but you can't precompute all
>> possible values, as the center of the search could possibly be anywhere.
>> Therefore you need something that makes such dynamic requests possible.
>>
>> Pure CouchDB could be used if you constrain your searches. You would
>> need to restrict to things like, a certain number for the center of
>> searches, only a fixed number of radii, and a fixed number of location
>> types (like banks, restaurants etc).
>>
>> Cheers,
>>   Volker
>>
> 
> I've asked on the #couchdb channel and got the same answer.
> 
> The 'Name Finder' on OSM http://wiki.openstreetmap.org/index.php/Name_finder
> divides the map to region and add a field to each element(place) indicating
> what region it belongs.
> When you make a search "banks near someRoad" it find in which region
> someRoad is and find all the banks in that road.
> So you are limited to predefined distances but the above design will work in
> couchdb as well.
> There is an assumption that they used this design because they used MySQL
> but I can't verify that.
> 
> My question is if arbitrary distances are not a requirement of my app, is it
> better to use couchdb for storing the geodata
> or is it better to use a spatial db like postGIS in any case.
> 
> Thanks

As much as I love CouchDB, your application sounds like a typical case
for PostGIS. The tools to import OSM data into PostGIS are there, and
you have a spatial index. Though you would obviously lose all the other
nice CouchDB features (like replication etc).

Cheers,
  Volker




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