[postgis-tickets] [PostGIS] #4798: ST_AsGeoJSON should warn about duplicate keys

[PostGIS]

#4798: ST_AsGeoJSON should warn about duplicate keys
----------------------------------+---------------------------
 Reporter:  tobwen                |      Owner:  pramsey
     Type:  enhancement           |     Status:  new
 Priority:  medium                |  Milestone:  PostGIS 3.1.0
Component:  postgis               |    Version:  master
 Keywords:  geojson, json, jsonb  |
----------------------------------+---------------------------
 == description
 Although all JSON specifications (RFC 8259, RFC 7159, RFC 4627, and
 ECMA-404) allow multiple columns with the same name, PostgreSQL's JSONB
 does not. JSONB just takes the last occurance.

 Most validators warn about duplicate columns, maybe PostGIS should warn
 about this, too? It might result in expected behaviour when storing as
 JSONB.

 == example
 {{{
 SELECT
     ST_AsGeoJSON(data.*)
 FROM
     (SELECT
         1 AS column,
         2 AS column,
         ST_Transform(geom, 3035) geom
     FROM
         ST_SetSRID(ST_MakePoint(7, 51), 4326) geom
     ) data;
 }}}

 == result JSON
 {{{
 {
   "type":"Feature",
   "geometry":{
     "type":"Point",
     "crs":{
       "type":"name",
       "properties":{
         "name":"EPSG:3035"
       }
     },
     "coordinates":[
       4110471.051819585,
       3103060.820290524
     ]
   },
   "properties":{
     "column":1,
     "column":2
   }
 }
 }}}

 == result JSONB
 {{{
 {
   "type":"Feature",
   "geometry":{
     "crs":{
       "type":"name",
       "properties":{
         "name":"EPSG:3035"
       }
     },
     "type":"Point",
     "coordinates":[
       4110471.051819585,
       3103060.820290524
     ]
   },
   "properties":{
     "column":2
   }
 }
 }}}

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4798>
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