DynamoDB Dynomite Migrations

Generating Migrations

Dynomite can generate migration files used to create DynamoDB tables. Example:

jets dynamodb:generate create_posts # generates migration
jets dynamodb:migrate               # run migrations

The table name will have a namespace. For example, if your project is called demo, the JETS_ENV=development, and you create a table called posts. The DynamoDB full table name will be demo-dev-posts. You can change this behavior by adjusting the table namespace value. See: Config.

Migration Example

You can use dynamodb:generate to create a starter migration file.

❯ jets dynamodb:generate create_posts
Migration file created: dynamodb/migrate/20230728152326-create_posts.rb

dynamodb/migrate/20230728152326-create_posts.rb

class CreatePosts < Dynomite::Migration
  def up
    create_table :posts do |t|
      t.partition_key :id # post-A2uxLhRzIYdqWwtN
      # Creating GSI with create_table now is much faster than using update_table later.
      # 20s vs 5m to 10m
      t.add_gsi :updated_at
    end
  end
end

More Examples:

Migration Types

DynamoDB tables support certain types of attribute types. The CLI will parse the --partition-key option and use the second part to map it to the underlying DynamoDB type. For example, --partition-key id:string maps string to S.

The migration types map to the DynamoDB Types. Here’s a snippet of from the source with the types map.

ATTRIBUTE_MAP = {
  string: 'S',
  number: 'N',
  binary: 'B',
  boolean: 'BOOL',
  null: 'NULL',
  map: 'M',
  list: 'L',
  string_set: 'SS',
  number_set: 'NS',
  binary_set: 'BS',
}

If a key is not in the map, it is passed through. So both id:string and id:S work. More info on DynamoDB types is available at the ruby aws-sdk docs: Aws::DynamoDB::Types::AttributeDefinition

class CreatePosts < Dynomite::Migration
  def up
    create_table :posts do |t|
      t.partition_key "id:S" # same as "id:string"
    end
  end
end

Here’s the source code: migration/dsl/types.rb

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