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Test for postgis

Project description

Summary

Add types and functions to work with geometric attributes that are stored in a Postgis database (that is a PostgreSQL database with Postgis extension enabled).

The present cube supports only version 2.0 and later of Postgis.

It introduces one new type when defining attributes in the data model schema:

  • a Geometry type. Additionally, you should give the following elements along with a Geometry attribute:
    • geom_type. The Postgis type of geometries that this attribute will accept, for example POINT, MULTILINESTRING or POLYGON,
    • srid. The spatial reference system the geometry coordinates will live in. This is an integer and a foreign key that must match the srid key in the spatial_ref_sys table. Most of the time, it will be the same as the spatial system EPSG code,
    • coord_dimension. The number of dimensions used by geometries. Defaults to 2.
  • a Geography type (see the description).

Then you can also use geometric functions like ST_INTERSECTS, ST_WITHIN or ST_UNION to work with this new type.

See Postgis manual for reference documentation about Postgis.

Example

In schema.py, one can declare a City entity like the following.

class City(EntityType):
    name = String(required=True)
    geometry = Geometry(geom_type='POLYGON', srid=4326)

You may then make queries like:

# get all cities in a given bounding box
rql('City C WHERE C geometry G HAVING(ST_WITHIN(G, ST_MAKEENVELOPE('
    '%(left)s, %(bottom)s, %(right)s, %(top)s, 4326)) = TRUE)',
        {'left': 2.2,
        'right': 2.6,
        'top': 49,
        'bottom': 48})

# get all cities at a given distance from a point, sorted by distance
rql('Any C, ST_DISTANCE(G, ST_SETSRID(ST_MAKEPOINT(2.2, 48.4), 4326)) '
    'ORDERBY 5 WHERE '
        'C geometry G HAVING ('
        ' ST_DWITHIN(G, ST_SETSRID(ST_MAKEPOINT(2.2, 48.4), 4326), 0.1) = TRUE)')

Project details


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