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639 lines
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639 lines
23 KiB
Plaintext
=============================
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Geographic Database Functions
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=============================
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.. module:: django.contrib.gis.db.models.functions
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:synopsis: Geographic Database Functions
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The functions documented on this page allow users to access geographic database
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functions to be used in annotations, aggregations, or filters in Django.
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Example:
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.. code-block:: pycon
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>>> from django.contrib.gis.db.models.functions import Length
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>>> Track.objects.annotate(length=Length("line")).filter(length__gt=100)
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Not all backends support all functions, so refer to the documentation of each
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function to see if your database backend supports the function you want to use.
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If you call a geographic function on a backend that doesn't support it, you'll
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get a ``NotImplementedError`` exception.
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Function's summary:
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========================= ======================== ====================== ======================= ================== ================== ======================
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Measurement Relationships Operations Editors Input format Output format Miscellaneous
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========================= ======================== ====================== ======================= ================== ================== ======================
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:class:`Area` :class:`Azimuth` :class:`Difference` :class:`ForcePolygonCW` :class:`AsGeoJSON` :class:`IsEmpty`
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:class:`Distance` :class:`BoundingCircle` :class:`Intersection` :class:`MakeValid` :class:`AsGML` :class:`IsValid`
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:class:`GeometryDistance` :class:`Centroid` :class:`SymDifference` :class:`Reverse` :class:`AsKML` :class:`MemSize`
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:class:`Length` :class:`Envelope` :class:`Union` :class:`Scale` :class:`AsSVG` :class:`NumGeometries`
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:class:`Perimeter` :class:`LineLocatePoint` :class:`SnapToGrid` :class:`FromWKB` :class:`AsWKB` :class:`NumPoints`
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:class:`PointOnSurface` :class:`Transform` :class:`FromWKT` :class:`AsWKT`
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:class:`Translate` :class:`GeoHash`
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========================= ======================== ====================== ======================= ================== ================== ======================
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``Area``
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========
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.. class:: Area(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-polygon-property-functions.html#function_st-area>`_,
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Oracle, `PostGIS <https://postgis.net/docs/ST_Area.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns the area of the
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field as an :class:`~django.contrib.gis.measure.Area` measure.
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MySQL and SpatiaLite without LWGEOM/RTTOPO don't support area calculations on
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geographic SRSes.
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``AsGeoJSON``
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=============
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.. class:: AsGeoJSON(expression, bbox=False, crs=False, precision=8, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-geojson-functions.html#function_st-asgeojson>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_AsGeoJSON.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns a `GeoJSON
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<https://geojson.org/>`_ representation of the geometry. Note that the result
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is not a complete GeoJSON structure but only the ``geometry`` key content of a
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GeoJSON structure. See also :doc:`/ref/contrib/gis/serializers`.
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Example:
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.. code-block:: pycon
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>>> City.objects.annotate(json=AsGeoJSON("point")).get(name="Chicago").json
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{"type":"Point","coordinates":[-87.65018,41.85039]}
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===================== =====================================================
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Keyword Argument Description
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===================== =====================================================
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``bbox`` Set this to ``True`` if you want the bounding box
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to be included in the returned GeoJSON. Ignored on
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Oracle.
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``crs`` Set this to ``True`` if you want the coordinate
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reference system to be included in the returned
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GeoJSON. Ignored on MySQL and Oracle.
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``precision`` It may be used to specify the number of significant
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digits for the coordinates in the GeoJSON
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representation -- the default value is 8. Ignored on
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Oracle.
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===================== =====================================================
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``AsGML``
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=========
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.. class:: AsGML(expression, version=2, precision=8, **extra)
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*Availability*: Oracle, `PostGIS <https://postgis.net/docs/ST_AsGML.html>`__,
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SpatiaLite
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Accepts a single geographic field or expression and returns a `Geographic Markup
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Language (GML)`__ representation of the geometry.
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Example:
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.. code-block:: pycon
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>>> qs = Zipcode.objects.annotate(gml=AsGML("poly"))
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>>> print(qs[0].gml)
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<gml:Polygon srsName="EPSG:4326"><gml:OuterBoundaryIs>-147.78711,70.245363 ...
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-147.78711,70.245363</gml:OuterBoundaryIs></gml:Polygon>
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===================== =====================================================
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Keyword Argument Description
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===================== =====================================================
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``precision`` Specifies the number of significant digits for the
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coordinates in the GML representation -- the default
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value is 8. Ignored on Oracle.
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``version`` Specifies the GML version to use: 2 (default) or 3.
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===================== =====================================================
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__ https://en.wikipedia.org/wiki/Geography_Markup_Language
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``AsKML``
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=========
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.. class:: AsKML(expression, precision=8, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_AsKML.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns a `Keyhole Markup
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Language (KML)`__ representation of the geometry.
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Example:
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.. code-block:: pycon
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>>> qs = Zipcode.objects.annotate(kml=AsKML("poly"))
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>>> print(qs[0].kml)
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<Polygon><outerBoundaryIs><LinearRing><coordinates>-103.04135,36.217596,0 ...
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-103.04135,36.217596,0</coordinates></LinearRing></outerBoundaryIs></Polygon>
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===================== =====================================================
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Keyword Argument Description
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===================== =====================================================
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``precision`` This keyword may be used to specify the number of
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significant digits for the coordinates in the KML
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representation -- the default value is 8.
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===================== =====================================================
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__ https://developers.google.com/kml/documentation/
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``AsSVG``
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=========
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.. class:: AsSVG(expression, relative=False, precision=8, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_AsSVG.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns a `Scalable Vector
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Graphics (SVG)`__ representation of the geometry.
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===================== =====================================================
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Keyword Argument Description
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===================== =====================================================
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``relative`` If set to ``True``, the path data will be implemented
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in terms of relative moves. Defaults to ``False``,
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meaning that absolute moves are used instead.
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``precision`` This keyword may be used to specify the number of
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significant digits for the coordinates in the SVG
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representation -- the default value is 8.
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===================== =====================================================
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__ https://www.w3.org/Graphics/SVG/
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``AsWKB``
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=========
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.. class:: AsWKB(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-format-conversion-functions.html#function_st-asbinary>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_AsBinary.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns a `Well-known
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binary (WKB)`_ representation of the geometry.
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Example:
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.. code-block:: pycon
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>>> bytes(City.objects.annotate(wkb=AsWKB("point")).get(name="Chelyabinsk").wkb)
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b'\x01\x01\x00\x00\x00]3\xf9f\x9b\x91K@\x00X\x1d9\xd2\xb9N@'
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``AsWKT``
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=========
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.. class:: AsWKT(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-format-conversion-functions.html#function_st-astext>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_AsText.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns a `Well-known text
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(WKT)`_ representation of the geometry.
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Example:
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.. code-block:: pycon
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>>> City.objects.annotate(wkt=AsWKT("point")).get(name="Chelyabinsk").wkt
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'POINT (55.137555 61.451728)'
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``Azimuth``
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===========
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.. class:: Azimuth(point_a, point_b, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_Azimuth.html>`__,
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SpatiaLite (LWGEOM/RTTOPO)
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Returns the azimuth in radians of the segment defined by the given point
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geometries, or ``None`` if the two points are coincident. The azimuth is angle
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referenced from north and is positive clockwise: north = ``0``; east = ``π/2``;
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south = ``π``; west = ``3π/2``.
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``BoundingCircle``
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==================
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.. class:: BoundingCircle(expression, num_seg=48, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_MinimumBoundingCircle.html>`__,
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`Oracle <https://docs.oracle.com/en/database/oracle/oracle-database/21/spatl/
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SDO_GEOM-reference.html#GUID-82A61626-BB64-4793-B53D-A0DBEC91831A>`_
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Accepts a single geographic field or expression and returns the smallest circle
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polygon that can fully contain the geometry.
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The ``num_seg`` parameter is used only on PostGIS.
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``Centroid``
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============
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.. class:: Centroid(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-polygon-property-functions.html#function_st-centroid>`__,
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`PostGIS <https://postgis.net/docs/ST_Centroid.html>`__, Oracle, SpatiaLite
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Accepts a single geographic field or expression and returns the ``centroid``
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value of the geometry.
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``Difference``
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==============
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.. class:: Difference(expr1, expr2, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-difference>`__,
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`PostGIS <https://postgis.net/docs/ST_Difference.html>`__, Oracle, SpatiaLite
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Accepts two geographic fields or expressions and returns the geometric
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difference, that is the part of geometry A that does not intersect with
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geometry B.
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``Distance``
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============
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.. class:: Distance(expr1, expr2, spheroid=None, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-relation-functions-object-shapes.html#function_st-distance>`__,
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`PostGIS <https://postgis.net/docs/ST_Distance.html>`__, Oracle, SpatiaLite
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Accepts two geographic fields or expressions and returns the distance between
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them, as a :class:`~django.contrib.gis.measure.Distance` object. On MySQL, a raw
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float value is returned when the coordinates are geodetic.
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On backends that support distance calculation on geodetic coordinates, the
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proper backend function is automatically chosen depending on the SRID value of
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the geometries (e.g. `ST_DistanceSphere
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<https://postgis.net/docs/ST_DistanceSphere.html>`__ on PostGIS).
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When distances are calculated with geodetic (angular) coordinates, as is the
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case with the default WGS84 (4326) SRID, you can set the ``spheroid`` keyword
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argument to decide if the calculation should be based on a simple sphere (less
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accurate, less resource-intensive) or on a spheroid (more accurate, more
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resource-intensive).
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In the following example, the distance from the city of Hobart to every other
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:class:`~django.contrib.gis.db.models.PointField` in the ``AustraliaCity``
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queryset is calculated:
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.. code-block:: pycon
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>>> from django.contrib.gis.db.models.functions import Distance
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>>> pnt = AustraliaCity.objects.get(name="Hobart").point
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>>> for city in AustraliaCity.objects.annotate(distance=Distance("point", pnt)):
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... print(city.name, city.distance)
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...
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Wollongong 990071.220408 m
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Shellharbour 972804.613941 m
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Thirroul 1002334.36351 m
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...
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.. note::
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Because the ``distance`` attribute is a
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:class:`~django.contrib.gis.measure.Distance` object, you can easily express
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the value in the units of your choice. For example, ``city.distance.mi`` is
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the distance value in miles and ``city.distance.km`` is the distance value
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in kilometers. See :doc:`measure` for usage details and the list of
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:ref:`supported_units`.
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``Envelope``
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============
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.. class:: Envelope(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-general-property-functions.html#function_st-envelope>`__,
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`Oracle <https://docs.oracle.com/en/database/oracle/oracle-database/21/spatl/
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spatial-operators-reference.html#GUID-ACED800F-3435-44AA-9606-D40934A23ED0>`__,
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`PostGIS <https://postgis.net/docs/ST_Envelope.html>`__, SpatiaLite
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Accepts a single geographic field or expression and returns the geometry
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representing the bounding box of the geometry.
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``ForcePolygonCW``
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==================
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.. class:: ForcePolygonCW(expression, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_ForcePolygonCW.html>`__,
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SpatiaLite
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Accepts a single geographic field or expression and returns a modified version
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of the polygon/multipolygon in which all exterior rings are oriented clockwise
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and all interior rings are oriented counterclockwise. Non-polygonal geometries
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are returned unchanged.
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``FromWKB``
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===========
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.. versionadded:: 4.2
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.. class:: FromWKB(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-wkb-functions.html#function_st-geomfromwkb>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_GeomFromWKB.html>`__, SpatiaLite
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Creates geometry from `Well-known binary (WKB)`_ representation.
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``FromWKT``
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===========
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.. versionadded:: 4.2
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.. class:: FromWKT(expression, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-wkt-functions.html#function_st-geomfromtext>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_GeomFromText.html>`__, SpatiaLite
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Creates geometry from `Well-known text (WKT)`_ representation.
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``GeoHash``
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===========
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.. class:: GeoHash(expression, precision=None, **extra)
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*Availability*: `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-geohash-functions.html#function_st-geohash>`__,
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`PostGIS <https://postgis.net/docs/ST_GeoHash.html>`__, SpatiaLite
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(LWGEOM/RTTOPO)
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Accepts a single geographic field or expression and returns a `GeoHash`__
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representation of the geometry.
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The ``precision`` keyword argument controls the number of characters in the
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result.
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__ https://en.wikipedia.org/wiki/Geohash
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``GeometryDistance``
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====================
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.. class:: GeometryDistance(expr1, expr2, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/geometry_distance_knn.html>`__
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Accepts two geographic fields or expressions and returns the distance between
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them. When used in an :meth:`~django.db.models.query.QuerySet.order_by` clause,
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it provides index-assisted nearest-neighbor result sets.
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``Intersection``
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================
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.. class:: Intersection(expr1, expr2, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-intersection>`__,
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`PostGIS <https://postgis.net/docs/ST_Intersection.html>`__, Oracle, SpatiaLite
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Accepts two geographic fields or expressions and returns the geometric
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intersection between them.
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``IsEmpty``
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===========
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.. versionadded:: 4.2
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.. class:: IsEmpty(expr)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_IsEmpty.html>`__
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Accepts a geographic field or expression and tests if the value is an empty
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geometry. Returns ``True`` if its value is empty and ``False`` otherwise.
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``IsValid``
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===========
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.. class:: IsValid(expr)
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*Availability*: `MySQL
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<https://dev.mysql.com/doc/refman/en/spatial-convenience-functions.html#function_st-isvalid>`__,
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`PostGIS <https://postgis.net/docs/ST_IsValid.html>`__, Oracle, SpatiaLite
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Accepts a geographic field or expression and tests if the value is well formed.
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Returns ``True`` if its value is a valid geometry and ``False`` otherwise.
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``Length``
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==========
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.. class:: Length(expression, spheroid=True, **extra)
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*Availability*: MariaDB, `MySQL
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<https://dev.mysql.com/doc/refman/en/gis-linestring-property-functions.html#function_st-length>`__,
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Oracle, `PostGIS <https://postgis.net/docs/ST_Length.html>`__, SpatiaLite
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Accepts a single geographic linestring or multilinestring field or expression
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and returns its length as a :class:`~django.contrib.gis.measure.Distance`
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measure.
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On PostGIS and SpatiaLite, when the coordinates are geodetic (angular), you can
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specify if the calculation should be based on a simple sphere (less
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accurate, less resource-intensive) or on a spheroid (more accurate, more
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resource-intensive) with the ``spheroid`` keyword argument.
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MySQL doesn't support length calculations on geographic SRSes.
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``LineLocatePoint``
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===================
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.. class:: LineLocatePoint(linestring, point, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_LineLocatePoint.html>`__,
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SpatiaLite
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Returns a float between 0 and 1 representing the location of the closest point on
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``linestring`` to the given ``point``, as a fraction of the 2D line length.
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``MakeValid``
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=============
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.. class:: MakeValid(expr)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_MakeValid.html>`__,
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SpatiaLite (LWGEOM/RTTOPO)
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Accepts a geographic field or expression and attempts to convert the value into
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a valid geometry without losing any of the input vertices. Geometries that are
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already valid are returned without changes. Simple polygons might become a
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multipolygon and the result might be of lower dimension than the input.
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``MemSize``
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===========
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.. class:: MemSize(expression, **extra)
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*Availability*: `PostGIS <https://postgis.net/docs/ST_MemSize.html>`__
|
|
|
|
Accepts a single geographic field or expression and returns the memory size
|
|
(number of bytes) that the geometry field takes.
|
|
|
|
``NumGeometries``
|
|
=================
|
|
|
|
.. class:: NumGeometries(expression, **extra)
|
|
|
|
*Availability*: MariaDB, `MySQL
|
|
<https://dev.mysql.com/doc/refman/en/gis-geometrycollection-property-functions.html#function_st-numgeometries>`__,
|
|
`PostGIS <https://postgis.net/docs/ST_NumGeometries.html>`__, Oracle,
|
|
SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns the number of
|
|
geometries if the geometry field is a collection (e.g., a ``GEOMETRYCOLLECTION``
|
|
or ``MULTI*`` field). Returns 1 for single geometries.
|
|
|
|
On MySQL, returns ``None`` for single geometries.
|
|
|
|
``NumPoints``
|
|
=============
|
|
|
|
.. class:: NumPoints(expression, **extra)
|
|
|
|
*Availability*: MariaDB, `MySQL
|
|
<https://dev.mysql.com/doc/refman/en/gis-linestring-property-functions.html#function_st-numpoints>`__,
|
|
`PostGIS <https://postgis.net/docs/ST_NPoints.html>`__, Oracle, SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns the number of points
|
|
in a geometry.
|
|
|
|
On MySQL, returns ``None`` for any non-``LINESTRING`` geometry.
|
|
|
|
``Perimeter``
|
|
=============
|
|
|
|
.. class:: Perimeter(expression, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_Perimeter.html>`__,
|
|
Oracle, SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns the perimeter of the
|
|
geometry field as a :class:`~django.contrib.gis.measure.Distance` object.
|
|
|
|
``PointOnSurface``
|
|
==================
|
|
|
|
.. class:: PointOnSurface(expression, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_PointOnSurface.html>`__,
|
|
MariaDB, Oracle, SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns a ``Point`` geometry
|
|
guaranteed to lie on the surface of the field; otherwise returns ``None``.
|
|
|
|
``Reverse``
|
|
===========
|
|
|
|
.. class:: Reverse(expression, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_Reverse.html>`__, Oracle,
|
|
SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns a geometry with
|
|
reversed coordinates.
|
|
|
|
``Scale``
|
|
=========
|
|
|
|
.. class:: Scale(expression, x, y, z=0.0, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_Scale.html>`__, SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns a geometry with
|
|
scaled coordinates by multiplying them with the ``x``, ``y``, and optionally
|
|
``z`` parameters.
|
|
|
|
``SnapToGrid``
|
|
==============
|
|
|
|
.. class:: SnapToGrid(expression, *args, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_SnapToGrid.html>`__,
|
|
SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns a geometry with all
|
|
points snapped to the given grid. How the geometry is snapped to the grid
|
|
depends on how many numeric (either float, integer, or long) arguments are
|
|
given.
|
|
|
|
=================== =====================================================
|
|
Number of Arguments Description
|
|
=================== =====================================================
|
|
1 A single size to snap both the X and Y grids to.
|
|
2 X and Y sizes to snap the grid to.
|
|
4 X, Y sizes and the corresponding X, Y origins.
|
|
=================== =====================================================
|
|
|
|
``SymDifference``
|
|
=================
|
|
|
|
.. class:: SymDifference(expr1, expr2, **extra)
|
|
|
|
*Availability*: MariaDB, `MySQL
|
|
<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-symdifference>`__,
|
|
`PostGIS <https://postgis.net/docs/ST_SymDifference.html>`__, Oracle,
|
|
SpatiaLite
|
|
|
|
Accepts two geographic fields or expressions and returns the geometric
|
|
symmetric difference (union without the intersection) between the given
|
|
parameters.
|
|
|
|
``Transform``
|
|
=============
|
|
|
|
.. class:: Transform(expression, srid, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_Transform.html>`__,
|
|
Oracle, SpatiaLite
|
|
|
|
Accepts a geographic field or expression and a SRID integer code, and returns
|
|
the transformed geometry to the spatial reference system specified by the
|
|
``srid`` parameter.
|
|
|
|
.. note::
|
|
|
|
What spatial reference system an integer SRID corresponds to may depend on
|
|
the spatial database used. In other words, the SRID numbers used for Oracle
|
|
are not necessarily the same as those used by PostGIS.
|
|
|
|
``Translate``
|
|
=============
|
|
|
|
.. class:: Translate(expression, x, y, z=0.0, **extra)
|
|
|
|
*Availability*: `PostGIS <https://postgis.net/docs/ST_Translate.html>`__,
|
|
SpatiaLite
|
|
|
|
Accepts a single geographic field or expression and returns a geometry with
|
|
its coordinates offset by the ``x``, ``y``, and optionally ``z`` numeric
|
|
parameters.
|
|
|
|
``Union``
|
|
=========
|
|
|
|
.. class:: Union(expr1, expr2, **extra)
|
|
|
|
*Availability*: MariaDB, `MySQL
|
|
<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-union>`__,
|
|
`PostGIS <https://postgis.net/docs/ST_Union.html>`__, Oracle, SpatiaLite
|
|
|
|
Accepts two geographic fields or expressions and returns the union of both
|
|
geometries.
|
|
|
|
.. _`Well-known binary (WKB)`: https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary
|
|
.. _`Well-known text (WKT)`: https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry
|