GeoPostGIS

Postgrex extension for the PostGIS data types. Uses the geo library

Documentation

Installation

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, "~> 1.0"}]
end

Examples

Postgrex Extension for the PostGIS data types, Geometry and Geography

  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.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