Rails: Converting from MySQL to PostGres breaks Geokit Distance Calculations?

问题

I recently switched my database from MySQL to PostGres. I also use GeoKit. When I started my app up with the new database already seeded, I get the following error:

PGError: ERROR:  function radians(character varying) does not exist
LINE 1: ...COS(0.661045389762993)*COS(-2.12957994527573)*COS(RADIANS(ti...
                                                         ^
HINT:  No function matches the given name and argument types. You might 
need to add explicit type casts.

Anyone know why this is breaking now? I know GeoKit still works because it's still performing the geocoding in the model per ticket when the database is seeded, it just won't do the distance calculations correctly.

回答1:

For those looking up this answer in the search, the problem is that Postgresql requires the lat, lng columns to be decimal or at least non-string whereas MySQL allows using both.

回答2:

Unsurprisingly the "radians" function expects a DOUBLE PRECISION argument. And there's no cast defined for TEXT/CHARACTER VARYING (a.k.a. VARCHAR) to DOUBLE PRECISION.

Probably the easiest solution is to define such a cast.

来源：https://stackoverflow.com/questions/2814968/rails-converting-from-mysql-to-postgres-breaks-geokit-distance-calculations