Defines a list of fields to use as a cursor when migrating a schema’s table to a new encryption key using mix cloak.migrate.

When to Use This

This behaviour is useful in rare situations where your primary key cannot be used as a cursor to page through the table. You need this if primary key cannot meet the “Column Requirements” below.

For example, you don’t need to use this module if your primary key is:

• An integer
• A PostgreSQL UUID
• A MongoDB ObjectID
• Your primary key already meets the “Column Requirements”

Column Requirements

Each column you specify for the cursor must meet the following requirements:

• Each column must contain sortable values
• Each column must be comparable using the > operator
• The combined value of the columns must be unique in the table

Example

defmodule MyApp.MySchema do
  use Ecto.Schema

  @behaviour Cloak.CustomCursor

  schema "table" do
    # ...
  end

  @impl Cloak.CustomCursor
  def __cloak_cursor_fields__ do
    [:sequential_id, :inserted_at]
  end
end