AshPostgresBelongsToIndex

Automatically adds AshPostgres custom indexes for belongs_to relationships in Ash resources.

Installation

Add ash_postgres_belongs_to_index to your list of dependencies in mix.exs:

def deps do
  [
    {:ash_postgres_belongs_to_index, "~> 0.3.0"}
  ]
end

Usage

defmodule Post do
  use Ash.Resource,
    data_layer: Ash.DataLayer.Postgres,
    extensions: [AshPostgresBelongsToIndex]

  postgres do
    table "post"
  end

  attributes do
    uuid_primary_key :id
    attribute :title, :string
    attribute :content, :string
  end

  relationships do
    belongs_to :user, User
  end
end

For the example above, the following index will be generated:

postgres do
  references do
    reference :user, index?: true
  end
end

Conflict detection

Indexes are only added when the FK is not already covered:

• A manual reference :user, index?: true is left alone.
• A manual reference :user, on_delete: :delete (no index?) still gets an index — added via custom_indexes, since a relationship can only have one reference entity.
• A custom index that covers the FK as its leftmost field(s) is respected, e.g. index [:user_id, :created_at] covers :user_id. Partial indexes (with a where clause) only count when the condition is the FK's own IS NOT NULL.

Only indexes declared in the resource DSL (custom_indexes / references) are considered. Indexes created by hand-written migrations are invisible to this plugin — declare them in custom_indexes, or exclude the relationship via except, to avoid duplicates.

Multitenancy

For attribute-based multitenancy, each FK gets both a composite [tenant_attr, fk_id] index (for tenant-scoped queries) and a single-column [fk_id] index with all_tenants?: true (FK constraint checks are not tenant-scoped, so the composite cannot serve them).

License

MIT