SQL Extensions

HEAVY.AI implements a number of custom extension functions to SQL.

Rendering

The following table describes SQL extensions available for the HEAVY.AI implementation of Vega.

SQL SELECT

Function	Arguments and Return
`convert_meters_to_merc_pixel_width(meters, lon, lat,` `min_lon``,` `max_lon``,` `img_width``,` `min_width``)`	Converts a distance in meters in a longitudinal direction from a latitude/longitude coordinate to a pixel size using mercator projection: `meters`: Distance in meters in a longitudinal direction to convert to pixel units. `lon`: Longitude coordinate of the center point to size from. `lat`: Latitude coordinate of the center point to size from. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `img_width`: The width in pixels of the view. `min_width`: Clamps the returned pixel size to be at least this width. Returns: Floating-point value in pixel units. Can be used for the width of a symbol or a point in Vega.
`convert_meters_to_merc_pixel_height(meters, lon, lat,` `min_lat``,` `max_lat``,` `img_height``,` `min_height``)`	Converts a distance in meters in a latitudinal direction from a latitude/longitude coordinate to a pixel size, using mercator projection: `meters`: Distance in meters in a longitudinal direction to convert to pixel units. `lon`: Longitude coordinate of the center point to size from. `lat`: Latitude coordinate of the center point to size from. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. `img_height`: The height in pixels of the view. `min_height`: Clamps the returned pixel size to be at least this height. Returns: Floating-point value in pixel units. Can be used for the height of a symbol or a point in Vega.
`convert_meters_to_pixel_width(meters,` `pt``,` `min_lon``,` `max_lon``,` `img_width``,` `min_width``)`	Converts a distance in meters in a longitudinal direction from a latitude/longitude POINT to a pixel size. Supports only mercator-projected points. `meters`: Distance in meters in a latitudinal direction to convert to pixel units. `pt`: The center POINT to size from. The point must be defined in the EPSG:4326 spatial reference system. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `img_width`: The width in pixels of the view. `min_width`: Clamps the returned pixel size to be at least this width. Returns: Floating-point value in pixel units. Can be used for the width of a symbol or a point in Vega.
`convert_meters_to_pixel_height(meters, pt,` `min_lat``,` `max_lat``,` `img_height``,` `min_height``)`	Converts a distance in meters in a latitudinal direction from an EPSG:4326 POINT to a pixel size. Currently only supports mercator-projected points: `meters`: Distance in meters in a longitudinal direction to convert to pixel units. `pt`: The center POINT to size from. The point must be defined in the EPSG:4326 spatial reference system. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. `img_height`: The height in pixels of the view. `min_height`: Clamps the returned pixel size to be at least this height. Returns: Floating-point value in pixel units. Can be used for the height of a symbol or a point in Vega.
`is_point_in_merc_view(lon, lat,` `min_lon``,` `max_lon``,` `min_lat``,` `max_lat``)`	Returns true if a latitude/longitude coordinate is within a mercator-projected view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`. `lon`: Longitude coordinate of the point. `lat`: Latitude coordinate of the point. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. Returns:True if the point is within the view defined by the `min_lon`/`max_lon`, `min_lat`/`max_lat`; otherwise, false.
`is_point_size_in_merc_view(lon, lat,` `meters``,` `min_lon``,` `max_lon``,` `min_lat``,` `max_lat``)`	Returns true if a latitude/longitude coordinate, offset by a distance in meters, is within a mercator-projected view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`. `lon`: Longitude coordinate of the point. `lat`: Latitude coordinate of the point. `meters`: Distance in meters to offset the point by, in any direction. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. Returns: True if the point is within the view defined by the `min_lon`/`max_lon`, `min_lat`/`max_lat`; otherwise, false.
`is_point_in_view(pt,` `min_lon``,` `max_lon``,` `min_lat``,` `max_lat``)`	Returns true if a latitude/longitude POINT defined in EPSG:4326 is within a mercator-projected view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`. `pt`: The POINT to check. Must be defined in EPSG:4326 spatial reference system. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. Returns: True if the point is within the view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`; otherwise, false.
`is_point_size_in_view(pt, meters,` `min_lon``,` `max_lon``,` `min_lat``,` `max_lat``)`	Returns true if a latitude/longitude POINT defined in EPSG:4326 is within a mercator-projected view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`. `pt`: The POINT to check. Must be defined in EPSG:4326 spatial reference system. `meters`: Distance in meters to offset the point by, in any direction. `min_lon`: Minimum longitude coordinate of the mercator-projected view. `max_lon`: Maximum longitude coordinate of the mercator-projected view. `min_lat`: Minimum latitude coordinate of the mercator-projected view. `max_lat`: Maximum latitude coordinate of the mercator-projected view. Returns: True if a latitude/longitude POINT defined in EPSG:4326, offset by a distance in meters, is within the view defined by `min_lon`/`max_lon`, `min_lat`/`max_lat`; otherwise, false.