79 lines
2.3 KiB
PL/PgSQL
79 lines
2.3 KiB
PL/PgSQL
--
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-- Function to "safely" transform to webmercator
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--
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-- This function works around the existance of a valid range
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-- for web mercator by "clipping" anything outside to the valid
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-- range.
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--
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CREATE OR REPLACE FUNCTION CDB_TransformToWebmercator(geom geometry)
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RETURNS geometry
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AS
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$$
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DECLARE
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valid_extent GEOMETRY;
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latlon_input GEOMETRY;
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clipped_input GEOMETRY;
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to_webmercator GEOMETRY;
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ret GEOMETRY;
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BEGIN
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IF ST_Srid(geom) = 3857 THEN
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RETURN geom;
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END IF;
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-- This is the valid web mercator extent
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--
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-- NOTE: some sources set the valid latitude range
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-- to -85.0511 to 85.0511 but as long as proj
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-- does not complain we are happy
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--
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valid_extent := ST_MakeEnvelope(-180, -89, 180, 89, 4326);
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-- Then we transform to WGS84 latlon, which is
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-- where we have known coordinates for the clipping
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--
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latlon_input := ST_Transform(geom, 4326);
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-- Don't bother clipping if the geometry boundary doesn't
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-- go outside the valid extent.
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IF latlon_input @ valid_extent THEN
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RETURN ST_Transform(latlon_input, 3857);
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END IF;
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-- Since we're going to use ST_Intersection on input
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-- we'd better ensure the input is valid
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-- TODO: only do this if the first ST_Intersection fails ?
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IF ST_Dimension(geom) != 0 AND
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-- See http://trac.osgeo.org/postgis/ticket/1719
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GeometryType(geom) != 'GEOMETRYCOLLECTION'
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THEN
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BEGIN
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latlon_input := ST_MakeValid(latlon_input);
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EXCEPTION
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WHEN OTHERS THEN
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-- See http://github.com/Vizzuality/cartodb/issues/931
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RAISE WARNING 'Could not clean input geometry: %', SQLERRM;
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RETURN NULL;
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END;
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latlon_input := ST_CollectionExtract(latlon_input, ST_Dimension(geom)+1);
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END IF;
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-- Then we clip, trying to retain the input type
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-- TODO: catch exceptions here too ?
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clipped_input := ST_Intersection(latlon_input, valid_extent);
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-- We transform to web mercator
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to_webmercator := ST_Transform(clipped_input, 3857);
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-- Finally we convert EMPTY to NULL
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-- See https://github.com/Vizzuality/cartodb/issues/706
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-- And retain "multi" status
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ret := CASE WHEN ST_IsEmpty(to_webmercator) THEN NULL::geometry
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WHEN GeometryType(geom) LIKE 'MULTI%' THEN ST_Multi(to_webmercator)
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ELSE to_webmercator
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END;
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RETURN ret;
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END
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$$ LANGUAGE 'plpgsql' IMMUTABLE STRICT PARALLEL UNSAFE;
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