Re: Confused about GeoDjango and PostGIS

25.4.2012 19:17, vishy kirjoitti:
> Hi,
>
> I need to do spatial queries like find places within 5 miles of a
> location given in latitude and longitude. So, I am thinking of
> exploring PostGIS and GeoDjango. I have installed both. Now, I already
> have a database which has a table for places with latitude and
> longitude. Can I enable this db to use postgis and add column to this
> table? Or, do I have to create a separate spatial db, create a table
> with a column of geometry type and import data into that table (from
> places table).? If I can use the existing database, how do I enable it
> to use PostGIS?
>

It depends on your environment but basic workflow is same is in *nix
instructions. And it's not even hard. :

createdb yourdatabase
createlang plpgsql yourdatabase
psql -d yourdatabase -f postgis.sql
psql -d yourdatabase -f postgis_comments.sql
psql -d yourdatabase -f spatial_ref_sys.sql


Of course in your case you can skip creation of database. Just create
language and install postgis stuff.

After that you need to make sure that your database user has access to
geometry_columns and spatial_ref_sys tables.

Add new column (For PostGIS 1.5.x, newer postgis has simpler alternative
syntax):

SELECT AddGeometryColumn('my_table', 'my_geom', 4326, 'POINT', 2)

And after that just update new geometry column:
update my_table set my_geom = GeomFromText('POINT(' + x + ' ' + y +')',
4326)

And don't forget to commit. If you have lot's of geometries (1M+) you
probably want to drop out spatial index and recreate it afterwards.
Otherwise building index takes just long time.


--
Jani Tiainen

- Well planned is half done and a half done has been sufficient before...

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