Manual actions allow you to control how an action is performed instead of dispatching to a data layer. To do this, specify the `manual` option with a module that adopts the appropriate behavior.
Manual actions are a way to implement an action in a fully custom way. This can be a very useful escape hatch when you have something that you are finding difficult to model with Ash's builtin tools.
For manual create, update and destroy actions, a module is passed that uses one of the following (`Ash.Resource.ManualCreate`, `Ash.Resource.ManualUpdate` and `Ash.Resource.ManualDestroy`).
The underlying record can be retrieved from `changeset.data` for update and destroy manual actions. The changeset given to the manual action will be after any `before_action` hooks, and before any `after_action` hooks.
Manual read actions work the same, except the will also get the "data layer query". For AshPostgres, this means you get the ecto query that would have been run.
As an alternative to manual read actions, you can also provide the `modify_query` option, which takes an `MFA` and allows low level manipulation of the query just before it is dispatched to the data layer.
For example:
```elixir
read :read do
modify_query {MyApp.ModifyQuery, :modify, []}
end
defmodule MyApp.ModifyQuery do
def modify(ash_query, data_layer_query) do
{:ok, modify_data_layer_query(data_layer_query)}
end
end
```
This can be used as a last-resort escape hatch when you want to still use resource actions but need to do something that you can't do easily with Ash tools. As with any low level escape hatch, here be dragons.