Getting started

You should already have Ecto installed and configured before proceeding. Please follow Ecto's Getting Started guide to get going first.

1. Add :commanded_ecto_projections to your list of dependencies in mix.exs:

   def deps do
     [
       {:commanded_ecto_projections, "~> 1.4"}
     ]
   end
   

2. Generate an Ecto migration in your app:

   $ mix ecto.gen.migration create_projection_versions
   

3. Modify the generated migration, in priv/repo/migrations, to create the projection_versions table:

   defmodule CreateProjectionVersions do
     use Ecto.Migration
   
     def change do
       create table(:projection_versions, primary_key: false) do
         add(:projection_name, :text, primary_key: true)
         add(:last_seen_event_number, :bigint)
   
         timestamps(type: :naive_datetime_usec)
       end
     end
   end
   

4. Run the Ecto migration:

   $ mix ecto.migrate
   

5. Define your first read model projector:

   defmodule MyApp.ExampleProjector do
     use Commanded.Projections.Ecto,
       application: MyApp.Application,
       repo: MyApp.Projections.Repo,
       name: "example_projection"
   end
   

Refer to the Usage guide for more detail on how to configure and use a read model projector.