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