DynamoDB Dynomite Model Unique Id

By default, dynomite a unique id upon creating an item. This field is id and will have the underscore class name and random characters. Example:

The id makes it easy to find an item regardless of whether or not you’re using Composite Keys.

Product.find("product-Q1xnDhRzIYduWAtU")

Related: find

Migration id Index

It would help if you always had an index on the id field so it’s quick to query for it. Example:

class CreateProducts < Dynomite::Migration
  def up
    create_table :products do |t|
      t.partition_key :category # required
      t.sort_key  "sku:number"  # optional. makes the primary key a composite key
      t.add_gsi :id
    end
  end
end

In the above example, we add a GSI index to the id field because the partition key is category. We cannot add an LSI index for the id field because LSI indexes must be Composite Keys by definition.

If you have the id as the partition key only:

class CreateProducts < Dynomite::Migration
  def up
    create_table :products do |t|
      t.partition_key "id" # required
    end
  end
end

Then you don’t need an additional index for id, since the key_schema has the partition_key id, and it’s already quick to look up with get_item. It’s essentially already indexed.

I generally prefer creating tables with a Primary Key Partition Key. A Composite Key can be created with GSI indexes if needed. See: Indexing.

Disable Magic Id

You can disable the setting of the magic id field by:

class Post < ApplicationItem
  disable_id!
end

Note: This only turns off the setting of it. An id field accessor is still available to simplify the implementation.

It is strongly recommended not to disable the id field. Without the id field some dynomite features may not work, like Associations. If you have a very good reason, we’re interested to know.