Rails - PostGIS + postgis_adapter Geometry Problem - ruby-on-rails

Question

I use postgis_adapter alongside with PostgreSQL 9.0.4, PostGIS 1.5.2 and Rails 3.1.0 on Ruby 1.9.2.
As described in the the postgis_adapter README, I tried to perform
Model.create(:geom => Point.from_x_y(10,20))
Postgres responds with
ERROR: parse error - invalid geometry
HINT: You must specify a valid OGC WKT geometry type such as POINT, LINESTRING or POLYGON
The created GeoRuby Object looks like this:
#<GeoRuby::SimpleFeatures::Point:0x0000010420a620 #srid=4326, #with_z=false, #with_m=false, #y=20, #x=10, #z=0.0, #m=0.0>
Hopefully someone got an idea.

Answer 1

Executive summary: it may work if you change it to:
Model.create(:the_name_of_your_geo_column => Point.from_x_y(10,20))
Longer version, with a high probability of Ruby howlers: I've barely written a word of rb but saw one too many great projects this week to continue in a state of ignorance. Working through the error messages in irb (starting from 0 in the language but very familiar with PostGIS):
ActiveRecord::Base.establish_connection(:adapter=>'postgresql',:database=>'moveable')
pt = TablePoint.new(:data => "Hello!",:geom => Point.from_x_y(1,2))
NameError: uninitialized constant Point
So, require 'postgis_adapter', but then:
PGError: ERROR: relation "table_points" does not exist
This must be that awesome naming convention in ActiveRecord that I've heard about. So create a table called table_points because I don't know what the database model/sync methods are.
moveable=> create table table_points(data text, geo_something geometry);
Notice here I used geometry rather than geography because my first instinct as to your problem was that the modeling methods in the database adapter layer created point types. Not at all, actually. Then again in irb,
pt = TablePoint.new(:geom => Point.from_x_y(1,2))
ActiveRecord::UnknownAttributeError: unknown attribute: geom
No attribute named geom? Just to see what would happen, again in psql:
moveable=> alter table table_points add column geom geometry;
ALTER TABLE
Then:
irb(main):014:0> pt = TablePoint.new(:geom => Point.from_x_y(10,20))
=> #<TablePoint data: nil, geo_something: nil, geom: #<GeoRuby::SimpleFeatures::Point:0x1022555f0 #y=20, #with_m=false, #x=10, #m=0.0, #with_z=false, #z=0.0, #srid=-1>>
irb(main):015:0> pt.save
=> true
Unbelievable! What if I did:
pt = TablePoint.new(:data => 'is this even possible?', :geom => Point.from_x_y(38,121), :geo_something => Point.from_x_y(37,120))
=> #<TablePoint data: "is this even possible?", geo_something: #<GeoRuby::SimpleFeatures::Point:0x102041098 #y=120, #with_m=false, #x=37, #m=0.0, #with_z=false, #z=0.0, #srid=-1>, geom: #<GeoRuby::SimpleFeatures::Point:0x1020410c0 #y=121, #with_m=false, #x=38, #m=0.0, #with_z=false, #z=0.0, #srid=-1>>
irb(main):023:0> pt.save
=> true
Even more unbelievable!
moveable=> select * from table_points;
data | geo_something | geom
--------+-----------------+--------
| | 0101000000000
| 010100000000000 |
| 010100000000000 |
...ble? | 00005E400000000 | 010000405E40
(4 rows)
I hesitate to post this as an answer because of fundamental lack of familiarity with Ruby but the above works (mindbendingly, to me), and you may be able to adapt it to your case.

Answer 2

My knowledge of Rails and Ruby is very limited, but try instead:
class Model < ActiveRecord::Base
end
pt = Model.new(:geom => Point.from_x_y(10,20))
pt.save

Answer 3

Adding a Spatial Reference System Identifier (SRID) fixed this problem for me:
Model.create(:geom => Point.from_x_y(10,20, 4326))
If you're using Google Maps, 4326 is the right SRID. Other maps and vendors might use something else.

Answer 4

I ran into a similar problem using spatial_adapter when upgrading a working app from Rails-3.0 to 3.1. It seems newer versions of ActiveRecord type cast your record to a GeoRuby object during insert. The activerecord-postgis-adapter correctly handles the type cast of your geometry column (presumably to EWKT). I spent a lot of time chasing this today and Aaron Patterson's response in this post was very helpful.
To fix your problem, upgrade your Gemfile and database.yml to use activerecord-postgis-adapter.