GEOMETRYCOLLECTION

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A GEOMETRYCOLLECTION is a collection of heterogeneous spatial objects, such as Points, LineStrings, Polygons, or other GEOMETRYCOLLECTIONs. It provides a way of referring to a group of spatial objects as one "thing" so that you can operate on it/them more conveniently using various SQL functions.

You can also store a GEOMETRYCOLLECTION with the following additional dimensions:

• A third dimension coordinate Z (GEOMETRYCOLLECTIONZ).
• A measure coordinate M (GEOMETRYCOLLECTIONM).
• Both a third dimension and a measure coordinate (GEOMETRYCOLLECTIONZM).

The Z and M dimensions can be accessed or modified using a number of built-in functions, including:

• ST_Z
• ST_M
• ST_Affine
• ST_Zmflag
• ST_MakePoint
• ST_MakePointM
• ST_Force3D
• ST_Force3DZ
• ST_Force3DM
• ST_Force4D
• ST_Snap
• ST_SnapToGrid
• ST_RotateZ
• ST_AddMeasure

Note that CockroachDB's spatial indexing is still based on the 2D coordinate system. This means that:

• The Z/M dimension is not index accelerated when using spatial predicates.
• Some spatial functions ignore the Z/M dimension, with transformations discarding the Z/M value.

Examples

A GeometryCollection can be created from SQL by calling the st_geomfromtext function on a GeometryCollection definition expressed in the Well Known Text (WKT) format as shown below.

SELECT ST_GeomFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0, 1440 900), POLYGON((0 0, 0 1024, 1024 1024, 1024 0, 0 0)))');

                                                                                                                                                              st_geomfromtext
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  0107000000030000000101000000000000000000000000000000000000000102000000020000000000000000000000000000000000000000000000008096400000000000208C40010300000001000000050000000000000000000000000000000000000000000000000000000000000000009040000000000000904000000000000090400000000000009040000000000000000000000000000000000000000000000000
(1 row)

See also

• Spatial tutorial
• Spatial objects
• POINT
• LINESTRING
• POLYGON
• MULTIPOINT
• MULTILINESTRING
• MULTIPOLYGON
• Using GeoServer with CockroachDB

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