Rescopes the default query on an Ecto schema.

An Ecto Schema is typically scoped by the Ecto.Schema.schema/2 macro, which defines the query as:

def __schema__(:query) do
  %Ecto.Query{
    from: %Ecto.Query.FromExpr{
      source: {unquote(source), __MODULE__},
      prefix: unquote(prefix)
    }
  }
end

This has a downside in that the schema cannot define a default scope for all queries to follow. For instance, perhaps one wants to ensure that soft-deleted records are not returned by default. To accomplish this, one might exclude any record with an is_deleted field set to true.

def without_deleted(query) do
  from(q in query, where: q.is_deleted == false)
end

Usage

By using the rescope/1 attribute or macro provided by Ecto.Rescope, one can override by passing a function that takes an Ecto.Query struct as the sole argument. This function must return an Ecto.Query struct.

NOTE: The macro must be invoked after the Ecto.Schema.schema/2 macro unless using an attribute. NOTE: The @rescope attribute does not accept anonymous functions.

Example

use Ecto.Rescope

@rescope &ThisModule.without_deleted/1
schema "user" do
  field(:is_deleted, :boolean)
end

def without_deleted(query) do
  from(q in query, where: q.is_deleted == false)
end

Using the macro directly.

Example

import Ecto.Rescope

schema "user" do
  field(:is_deleted, :boolean)
end

rescope(&without_deleted/1)

def without_deleted(query) do
  from(q in query, where: q.is_deleted == false)
end

At this point, any queries using the schema will now be defined with the new default scope.