[PostGIS] #5775: ST_AsGeoJSONAgg which is aggregate version of ST_AsGeoJSON

[PostGIS]

#5775: ST_AsGeoJSONAgg which is aggregate version of ST_AsGeoJSON
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 Reporter:  robe     |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 3.5.0
Component:  postgis  |    Version:  master
 Keywords:           |
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 I was thinking about this some, and realized when I want to use
 ST_AsGeoJSON, I usually combine it with something like jsonb_buildobject
 or json_buildobject, cause ST_AsGeoJSON has no version that supports
 aggregates like ST_AsMVT has.

 Wouldn't it be nice if one could do this:


 {{{
 SELECT ST_AsGeoJSONAgg(t.*, id_column => 'id')::json
 FROM ( VALUES (1, 'one', 'POINT(1 1)'::geometry),
               (2, 'two', 'POINT(2 2)'),
               (3, 'three', 'POINT(3 3)')
      ) as t(id, name, geom);
 }}}


 and it would output the same result as what this does


 {{{
 SELECT json_build_object(
     'type', 'FeatureCollection',
     'features', json_agg(ST_AsGeoJSON(t.*, id_column => 'id')::json)
     )
 FROM ( VALUES (1, 'one', 'POINT(1 1)'::geometry),
               (2, 'two', 'POINT(2 2)'),
               (3, 'three', 'POINT(3 3)')
      ) as t(id, name, geom);
 }}}

 Now sadly we can't overload ST_AsGeoJSON here, for the same reason
 we couldn't overload ST_Union,
 cause the above would be ambiguous as to if you want to aggregate or do
 row by row.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5775>
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