Ecto.Adapter behaviour (Ecto v3.5.0-rc.1) View Source
Specifies the minimal API required from adapters.
Link to this section Summary
Callbacks
The callback invoked in case the adapter needs to inject code.
Checks out a connection for the duration of the given function.
Returns the dumpers for a given type.
Ensure all applications necessary to run the adapter are started.
Initializes the adapter supervision tree by returning the children and adapter metadata.
Returns the loaders for a given type.
Link to this section Types
Specs
adapter_meta() :: map()
The metadata returned by the adapter init/1
.
It must be a map and Ecto itself will always inject two keys into the meta:
- the
:cache
key, which as ETS table that can be used as a cache (if available) - the
:pid
key, which is the PID returned by the child spec returned ininit/1
Specs
t() :: module()
Link to this section Functions
Returns the adapter metadata from the init/1
callback.
It expects a name or a PID representing a repo.
Link to this section Callbacks
Specs
__before_compile__(term(), env :: Macro.Env.t()) :: Macro.t()
The callback invoked in case the adapter needs to inject code.
Specs
checkout(adapter_meta(), config :: Keyword.t(), (() -> result)) :: result when result: var
Checks out a connection for the duration of the given function.
In case the adapter provides a pool, this guarantees all of the code
inside the given fun
runs against the same connection, which
might improve performance by for instance allowing multiple related
calls to the datastore to share cache information:
Repo.checkout(fn ->
for _ <- 100 do
Repo.insert!(%Post{})
end
end)
If the adapter does not provide a pool, just calling the passed function and returning its result are enough.
If the adapter provides a pool, it is supposed to "check out" one of the
pool connections for the duration of the function call. Which connection
is checked out is not passed to the calling function, so it should be done
using a stateful method like using the current process' dictionary, process
tracking, or some kind of other lookup method. Make sure that this stored
connection is then used in the other callbacks implementations, such as
Ecto.Adapter.Queryable
and Ecto.Adapter.Schema
.
Specs
dumpers(primitive_type :: Ecto.Type.primitive(), ecto_type :: Ecto.Type.t()) :: [(term() -> {:ok, term()} | :error) | Ecto.Type.t()]
Returns the dumpers for a given type.
It receives the primitive type and the Ecto type (which may be primitive as well). It returns a list of dumpers with the given type usually at the beginning.
This allows developers to properly translate values coming from the Ecto into adapter ones. For example, if the database does not support booleans but instead returns 0 and 1 for them, you could add:
def dumpers(:boolean, type), do: [type, &bool_encode/1]
def dumpers(_primitive, type), do: [type]
defp bool_encode(false), do: {:ok, 0}
defp bool_encode(true), do: {:ok, 1}
All adapters are required to implement a clause for :binary_id types,
since they are adapter specific. If your adapter does not provide
binary ids, you may simply use Ecto.UUID
:
def dumpers(:binary_id, type), do: [type, Ecto.UUID]
def dumpers(_primitive, type), do: [type]
Specs
ensure_all_started( config :: Keyword.t(), type :: :permanent | :transient | :temporary ) :: {:ok, [atom()]} | {:error, atom()}
Ensure all applications necessary to run the adapter are started.
Specs
init(config :: Keyword.t()) :: {:ok, :supervisor.child_spec(), adapter_meta()}
Initializes the adapter supervision tree by returning the children and adapter metadata.
Specs
loaders(primitive_type :: Ecto.Type.primitive(), ecto_type :: Ecto.Type.t()) :: [(term() -> {:ok, term()} | :error) | Ecto.Type.t()]
Returns the loaders for a given type.
It receives the primitive type and the Ecto type (which may be primitive as well). It returns a list of loaders with the given type usually at the end.
This allows developers to properly translate values coming from the adapters into Ecto ones. For example, if the database does not support booleans but instead returns 0 and 1 for them, you could add:
def loaders(:boolean, type), do: [&bool_decode/1, type]
def loaders(_primitive, type), do: [type]
defp bool_decode(0), do: {:ok, false}
defp bool_decode(1), do: {:ok, true}
All adapters are required to implement a clause for :binary_id
types,
since they are adapter specific. If your adapter does not provide binary
ids, you may simply use Ecto.UUID
:
def loaders(:binary_id, type), do: [Ecto.UUID, type]
def loaders(_primitive, type), do: [type]