Postgrex extension for the PostGIS data types. Uses the geo library
If available in Hex, the package can be installed
by adding geo_postgis
to your list of dependencies in mix.exs
:
def deps do
[{:geo_postgis, "~> 2.0"}]
end
When a binary is passed to `Geo.PostGIS.Geometry.cast/1` implementation of `Ecto.Type.cast/1`, it is assumed to be a GeoJSON string. When this happens, geo_postgis will use Poison, by default, to convert the binary to a map and then convert that map to on of the Geo structs. If in these cases you would like to use a different JSON parser, you can set the config below.
# config.exs
config :geo_postgis,
json_library: Poison # If you want to set your JSON module
Postgrex.Types.define(MyApp.PostgresTypes, [Geo.PostGIS.Extension], [])
opts = [hostname: "localhost", username: "postgres", database: "geo_postgrex_test", types: MyApp.PostgresTypes ]
[hostname: "localhost", username: "postgres", database: "geo_postgrex_test", types: MyApp.PostgresTypes]
{:ok, pid} = Postgrex.Connection.start_link(opts)
{:ok, #PID<0.115.0>}
geo = %Geo.Point{coordinates: {30, -90}, srid: 4326}
%Geo.Point{coordinates: {30, -90}, srid: 4326}
{:ok, _} = Postgrex.Connection.query(pid, "CREATE TABLE point_test (id int, geom geometry(Point, 4326))")
{:ok, %Postgrex.Result{columns: nil, command: :create_table, num_rows: 0, rows: nil}}
{:ok, _} = Postgrex.Connection.query(pid, "INSERT INTO point_test VALUES ($1, $2)", [42, geo])
{:ok, %Postgrex.Result{columns: nil, command: :insert, num_rows: 1, rows: nil}}
Postgrex.Connection.query(pid, "SELECT * FROM point_test")
{:ok, %Postgrex.Result{columns: ["id", "geom"], command: :select, num_rows: 1,
rows: [{42, %Geo.Point{coordinates: {30.0, -90.0}, srid: 4326 }}]}}
Use with Ecto Referencing the documentation:
#If using with Ecto, you may want something like thing instead
Postgrex.Types.define(MyApp.PostgresTypes,
[Geo.PostGIS.Extension] ++ Ecto.Adapters.Postgres.extensions(),
json: Poison)
#Add extensions to your repo config
config :thanks, Repo,
database: "geo_postgrex_test",
username: "postgres",
password: "postgres",
hostname: "localhost",
adapter: Ecto.Adapters.Postgres,
types: MyApp.PostgresTypes
#Create a model
defmodule Test do
use Ecto.Model
schema "test" do
field :name, :string
field :geom, Geo.PostGIS.Geometry
end
end
#Geometry or Geography columns can be created in migrations too
defmodule Repo.Migrations.Init do
use Ecto.Migration
def up do
create table(:test) do
add :name, :string
add :geom, :geometry
end
end
def down do
drop table(:test)
end
end
Ecto migrations can also use more elaborate Postgis GIS Objects. These types are useful for enforcing constraints on {Lng,Lat} (order matters), or ensuring that a particular projection/coordinate system/format is used.
defmodule Repo.Migrations.AdvancedInit do
use Ecto.Migration
def up do
create table(:test) do
add :name, :string
end
# Add a field `lng_lat_point` with type `geometry(Point,4326)`.
# This can store a "standard GPS" (epsg4326) coordinate pair {longitude,latitude}.
execute("SELECT AddGeometryColumn ('test','lng_lat_point',4326,'POINT',2);")
end
def down do
drop table(:test)
end
end
Be sure to enable the Postgis extension if you haven't already done so:
defmodule MyApp.Repo.Migrations.EnablePostgis do
use Ecto.Migration
def up do
execute "CREATE EXTENSION IF NOT EXISTS postgis"
end
def down do
execute "DROP EXTENSION IF EXISTS postgis"
end
end
Postgis functions can also be used in ecto queries. Currently only the OpenGIS functions are implemented. Have a look at lib/geo_postgis.ex for the implemented functions. You can use them like:
defmodule Example do
import Ecto.Query
import Geo.PostGIS
def example_query(geom) do
from location in Location, limit: 5, select: st_distance(location.geom, ^geom)
end
end
After you got the dependencies via mix deps.get
make sure that:
postgis
is installed- your
postgres
user has the database"geo_postgrex_test"
- your
postgres
db user can login without a password or you set thePGPASSWORD
environment variable appropriately
Then you can run the tests as you are used to with mix test
.