Add Ibis support for geospatial data types and functions

[xmnlab]

Geospatial Primitive Types

POINT:

• A point described by two coordinates.
• Ex: POINT(0 0)

LINESTRING:

• A sequence of 2 or more points and the lines that connect them.
• Ex: LINESTRING(0 0,1 1,1 2)

POLYGON:

• A set of one or more rings (closed line strings), with the first representing the shape (external ring) and the rest representing holes in that shape (internal rings).
• Ex: POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

MULTIPOLYGON:

• A set of one or more polygons.
• Ex: MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

OmniSci supports SRIDs 4326 and 900913. You can specify the SRID of your geometry field when creating the table:

• create table simple_geo (name text encoding dict(32), pt geometry(point,4326));

If you did not set the SRID of your geo field in the table, you need to set it in your SQL code. The following query uses ST _DISTANCE, sets the SRID to 4326, and casts the geospatial point field as a geography to return the distance in meters:

• select a.name, st_distance( cast(st_setsrid(a.pt,4326) as geography), cast(st_setsrid(b.pt.4326) as geography) ) as dist_meters from starting_point a, destination_points b;

Geospatial Literals

Geospatial functions that expect geospatial object arguments accept geospatial columns, geospatial objects returned by other functions, or string literals containing WKT representations of geospatial objects. Supplying a WKT string is equivalent to calling a geometry constructor. For example, these two queries are identical:

SELECT count() from geo1 where ST_Distance(p1, ‘POINT(1 2)’) < 1.0; SELECT count() from geo1 where ST_Distance(p1, ST_GeomFromText(‘POINT(1 2)’));

Geospatial functions

• Geometry/Geography Constructors
  • [x] ST_GeomFromText(WKT) - using literals
  • [x] ST_GeogFromText(WKT) - using literals
• Geometry Editors
  • [ ] ST_Transform (Returns a new geometry with its coordinates transformed to a different spatial reference system.)
  • [ ] ST_SetSRID (Sets the SRID on a geometry to a particular integer value.)
• Geometry Accessors
  • [x] ST_X (Return the X coordinate of the point, or NULL if not available. Input must be a point.)
  • [x] ST_Y (Return the Y coordinate of the point, or NULL if not available. Input must be a point.)
  • [x] ST_XMin (Returns Y minima of a bounding box 2d or 3d or a geometry.)
  • [x] ST_XMax (Returns X maxima of a bounding box 2d or 3d or a geometry.)
  • [x] ST_YMin (Returns Y minima of a bounding box 2d or 3d or a geometry.)
  • [x] ST_YMax (Returns Y maxima of a bounding box 2d or 3d or a geometry.)
  • [x] ST_StartPoint (Returns the first point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING.)
  • [x] ST_EndPoint (Returns the last point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING.)
  • [x] ST_PointN (Return the Nth point in a single linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry.)
  • [x] ST_NPoints (Return the number of points in a geometry. Works for all geometries.)
  • [x] ST_NRings (If the geometry is a polygon or multi-polygon returns the number of rings. It counts the outer rings as well.)
  • [x] ST_SRID (Returns the spatial reference identifier for the ST_Geometry)
• Spatial Relationships and Measurements
  • [x] ST_Distance
  • [x] ST_Contains
  • [x] ST_Area
  • [x] ST_Perimeter
  • [x] ST_Length
  • [x] ST_MaxDistance
• Extra
  • [ ] CastToGeography

References

• https://www.omnisci.com/docs/latest/5_geospatial_functions.html

[xmnlab]

the missing 3 features will be addressed in a new issue.