The SE_BBoxFromBSON() function

The SE_BBoxFromBSON() function takes a bson value with spatial data following the GeoJSON specification and a JSON path in a VARCHAR string, and returns an ST_Polygon object.

Syntax

create function SE_BBoxFromBSON(bson,varchar(255))
returns ST_Polygon

Return type

ST_Polygon

Example

The city engineer wants to know the “Bounding Box” of a city.

The following code inserts one row for GeoJSON geometry type Polygon.

-- create a table of bson value containing GeoJson spatial values under the city tag
create table bson_tab (pid serial, geometry bson, type varchar(16));
Table created.

insert into bson_tab values(0, ('{
		"city":{
			"type":"Polygon",
			"coordinates" : [[[0, 0], [10, 0], [10, 10], [0, 10], [0, 0]], [[2, 2], [8, 2], [8, 8], [2, 8], [2, 2]]]
		}
	 }'::json)::bson,
	'Polygon');
1 row(s) inserted.

The query selects a bounding box value from the table by using SE_BBoxFromBSON.

select pid, se_bboxfrombson(geometry, 'city') from bson_tab;

This is the result.

pid           1
(expression)  4326 POLYGON ((2.9999999 1.9999999, 3.0000001 1.9999999, 3.000000
              1 2.0000001, 2.9999999 2.0000001, 2.9999999 1.9999999)) 

pid           2
(expression)  4326 POLYGON ((1 0, 4 0, 4 5, 1 5, 1 0)) 

pid           3
(expression)  4326 POLYGON ((0 0, 10 0, 10 10, 0 10, 0 0)) 

pid           4
(expression)  4326 POLYGON ((1 0, 4 0, 4 5, 1 5, 1 0)) 

pid           5
(expression)  4326 POLYGON ((1 0, 135 0, 135 21, 1 21, 1 0)) 

pid           6
(expression)  4326 POLYGON ((0 0, 28 0, 28 28, 0 28, 0 0)) 

6 row(s) retrieved.