toland / schemata

Migration tool for Elixir projects using Cassandra

Schemata

Some simple Cassandra migration tasks for Mix.

Migrations

First we define our migrations. These are just ordinary Elixir files in priv/migrations that have some added metadata. For instance, we could want a table to store our import foobar data.

defmodule Schemata.CreateFoobarsMigration do
  use Schemata.Migration, [
    authored_at: "2016-07-22T03:28:53Z",
    description: "Create the foobars table"
  ]

  def up do
    create_table "foobars", in: "test",
      columns: [
        foo: :text,
        bar: :text
      ],
      primary_key: [:foo, :bar]
  end

  def down do
    drop :table, named: "foobars", in: "test"
  end
end

Schemata will load these Elixir files for us, and let us view all migrations with schemata.migrations.

$ mix schemata.migrations
Status   Name                                    Description
---------------------------------------------------------------------------------
up       1464076712285_create_foobars.exs        Creates the foobars table
up       1464076931287_create_users_table.exs    Adds qux to foobars
up       1464078503735_add_foobar_keyspace.exs   Adds the foobar keyspace
up       1464078511522_add_baz_table.exs         Makes the table baz

Let's rollback that last one with schemata.rollback.

$ mix schemata.rollback

01:32:32.203 [info]  == Migrating priv/migrations/1464078511522_add_baz_table.exs down

01:32:32.359 [info]  == Migrated in 1.5s

Listing them again shows the result of the rollback.

$ mix schemata.migrations
Status   Name                                    Description
---------------------------------------------------------------------------------
up       1464076712285_create_foobars.exs        Creates the foobars table
up       1464076931287_create_users_table.exs    Adds qux to foobars
up       1464078503735_add_foobar_keyspace.exs   Adds the foobar keyspace
down     1464078511522_add_baz_table.exs         Makes the table baz

So let's undo that and apply all pending migrations with schemata.migrate...

$ mix schemata.migrate

01:33:20.025 [info]  == Migrating priv/migrations/1464078511522_add_baz_table.exs up

01:33:20.224 [info]  == Migrated in 1.0s

and show that they're all done again!

$ mix schemata.migrations
Status   Name                                    Description
---------------------------------------------------------------------------------
up       1464076712285_create_foobars.exs        Creates the foobars table
up       1464076931287_create_users_table.exs    Adds qux to foobars
up       1464078503735_add_foobar_keyspace.exs   Adds the foobar keyspace
up       1464078511522_add_baz_table.exs         Makes the table baz

Installation

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

   def deps do [{:schemata, "~> 0.1.0"}] end

2. Ensure schemata is started before your application:

   def application do [applications: [:schemata]] end