[postgis-tickets] [PostGIS] #2965: ST_Distance, use_spheroid default

[PostGIS]

#2965: ST_Distance, use_spheroid default
-----------------------+----------------------------------------------------
  Reporter:  gitai     |       Owner:  pramsey                  
      Type:  defect    |      Status:  closed                   
  Priority:  critical  |   Milestone:  PostGIS 2.1.5            
 Component:  postgis   |     Version:  2.1.x                    
Resolution:  wontfix   |    Keywords:  ST_Distance, use_spheroid
-----------------------+----------------------------------------------------

Comment(by robe):

 autocast is never done per function, its done with a cast object and
 automatically applies to all function.  The thing that controls it is
 this:


 {{{
 CREATE CAST (geometry AS geography)
   WITH FUNCTION postgis.geography(geometry)
   AS IMPLICIT;



 }}}

 Note the term -- IMPLICIT  (that means that if there is a function for
 geography and no equivalent for geometry, then geometry can auto cast
 itself to geography to use it)

 So if you want to experiment yourself with what pramsey is proposing do
 this:


 {{{
 -- this line needed if you installed postgis as an extension
 ALTER EXTENSION postgis DROP CAST (geometry AS geography);
 DROP CAST (geometry AS geography);

  CREATE CAST (geometry AS geography)
   WITH FUNCTION geography(geometry)
   AS ASSIGNMENT;


 --this line needed if you installed postgis as an extension
 ALTER EXTENSION postgis ADD CAST (geometry AS geography);

 }}}


 Once you do that, you'll see that this no longer works


 {{{
 select ST_Distance(ST_SetSRID(ST_MakePoint(-73.9662500, 40.7834300),
 4326), ST_SetSRID(ST_MakePoint(-74.1960983, 40.739418), 4326), true);
 }}}

 and you have to explicitly cast to
 {{{
 select ST_Distance(ST_SetSRID(ST_MakePoint(-73.9662500, 40.7834300),
 4326)::geography, ST_SetSRID(ST_MakePoint(-74.1960983, 40.739418),
 4326)::geography, true);
 }}}


 As a general rule, all constructor functions (except for the ones that
 have ST_Geog.. or that explicitly take in input as geography return
 geometry (not geography).

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/2965#comment:19>
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