Behaviour describing what analysis capabilities a given Ash data layer supports.
AshDyan ships with implementations for AshPostgres and Ash.DataLayer.Simple
(ETS). Other data layers fall back to a default that supports only the
universally-safe capabilities (:frequency, :aggregate) and rejects
:time_bucket/:percentile with a clear error rather than silently wrong
results.
The capability check is surfaced explicitly via AshDyan.supports?/2 so
callers can discover data-layer limits before issuing a query.
Extending with third-party data layers
The mapping from an Ash data-layer module to its AshDyan.DataLayer
capability implementation is config-mergeable, so a downstream app can register
its own data layer without patching AshDyan:
config :ash_dyan, :data_layer_capabilities, %{
MyApp.CustomDataLayer => MyApp.AshDyan.CustomCapabilities
}Or via an extension:
defmodule MyApp.AshDyan.Extension do
@behaviour AshDyan.Extension
def data_layer_capabilities do
%{
MyApp.CustomDataLayer => MyApp.AshDyan.CustomCapabilities
}
end
end
config :ash_dyan, :extensions, [MyApp.AshDyan.Extension]Summary
Callbacks
Optional callback for SQL-pushdown of time bucketing.
Functions
Resolve the data-layer capability module for a resource.
Returns true if the resource's data layer supports the capability.
Callbacks
@callback paginate(Ash.Query.t(), pos_integer(), pos_integer()) :: {:ok, Ash.Query.t()} | {:error, term()}
@callback pushdown_aggregate(Ash.Query.t(), atom(), atom()) :: {:ok, Ash.Query.t()} | :not_supported
@callback pushdown_time_bucket(Ash.Query.t(), atom(), AshDyan.time_bucket()) :: {:ok, Ash.Query.t()} | :not_supported
Optional callback for SQL-pushdown of time bucketing.
A data layer that can express a time bucket natively (e.g. Postgres
date_trunc) implements this and returns {:ok, query}. The default returns
:not_supported, in which case the engine falls back to in-memory bucketing.
@callback stream(Ash.Query.t(), keyword(), keyword()) :: {:ok, Enumerable.t()} | {:error, term()}
@callback supports?(module(), AshDyan.capability()) :: boolean()
Functions
Resolve the data-layer capability module for a resource.
Built-in mappings are merged with config :ash_dyan, :data_layer_capabilities
and extension configurations, so third-party data layers can register their
own capability module.
@spec supports?(module(), AshDyan.capability()) :: boolean()
Returns true if the resource's data layer supports the capability.