Ecto

v2.0.2

Ecto v2.0.2 Ecto.Adapter behaviour

This module specifies the adapter API that an adapter is required to implement.

Summary

Types

autogenerate_id()
cached()
constraints()
fields()
filters()
prepared()
process()
query_meta()

Ecto.Query metadata fields (stored in cache)

returning()
schema_meta()

Ecto.Schema metadata fields

source()
t()

Callbacks

__before_compile__(env)

The callback invoked in case the adapter needs to inject code

autogenerate(field_type)

Called to autogenerate a value for id/embed_id/binary_id

child_spec(repo, options)

Returns the childspec that starts the adapter process

delete(repo, schema_meta, filters, options)

Deletes a single struct with the given filters

dumpers(primitive_type, ecto_type)

Returns the dumpers for a given type

ensure_all_started(repo, type)

Ensure all applications necessary to run the adapter are started

execute(repo, query_meta, query, params, arg4, options)

Executes a previously prepared query

insert(repo, schema_meta, fields, returning, options)

Inserts a single new struct in the data store

insert_all(repo, schema_meta, header, list, returning, options)

Inserts multiple entries into the data store

loaders(primitive_type, ecto_type)

Returns the loaders for a given type

prepare(atom, query)

Commands invoked to prepare a query for all, update_all and delete_all

update(repo, schema_meta, fields, filters, returning, options)

Updates a single struct with the given filters

Types 

autogenerate_id ::
  {field :: atom, type :: :id | :binary_id, value :: term} |
  nil
cached :: term
prepared :: term
process :: (field :: Macro.t, value :: term, context :: term -> term)
query_meta :: %{prefix: binary | nil, sources: tuple, assocs: term, preloads: term, select: term, fields: [term]}

Ecto.Query metadata fields (stored in cache)

returning :: [atom]
schema_meta :: %{source: source, schema: atom, context: term, autogenerate_id: {atom, :id | :binary_id}}

Ecto.Schema metadata fields

source :: {prefix :: binary | nil, table :: binary}
t :: module

Callbacks

__before_compile__(env)

Specs

__before_compile__({line :: Macro.Env.line, env :: Macro.Env.t}, env :: Macro.Env.t) :: Macro.t

The callback invoked in case the adapter needs to inject code.

autogenerate(field_type)

Specs

autogenerate(field_type :: :id | :binary_id | :embed_id) ::
  term |
  nil |
  no_return

Called to autogenerate a value for id/embed_id/binary_id.

Returns the autogenerated value, or nil if it must be autogenerated inside the storage or raise if not supported.

child_spec(repo, options)

Specs

child_spec(repo, options) :: Supervisor.Spec.spec

Returns the childspec that starts the adapter process.

delete(repo, schema_meta, filters, options)

Specs

delete(repo, schema_meta, filters, options) ::
  {:ok, fields} |
  {:invalid, constraints} |
  {:error, :stale} |
  no_return

Deletes a single struct with the given filters.

While filters can be any record column, it is expected that at least the primary key (or any other key that uniquely identifies an existing record) be given as a filter. Therefore, in case there is no record matching the given filters, {:error, :stale} is returned.

dumpers(primitive_type, ecto_type)

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 or :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]
ensure_all_started(repo, type)

Specs

ensure_all_started(repo, type :: :application.restart_type) ::
  {:ok, [atom]} |
  {:error, atom}

Ensure all applications necessary to run the adapter are started.

execute(repo, query_meta, query, params, arg4, options)

Specs

execute(repo, query_meta, query, params :: list, process | nil, options) :: result when result: {integer, [[term]] | nil} | no_return, query: {:nocache, prepared} | {:cached, cached} | {:cache, (cached -> :ok), prepared}

Executes a previously prepared query.

It must return a tuple containing the number of entries and the result set as a list of lists. The result set may also be nil if a particular operation does not support them.

The meta field is a map containing some of the fields found in the Ecto.Query struct.

It receives a process function that should be invoked for each selected field in the query result in order to convert them to the expected Ecto type. The process function will be nil if no result set is expected from the query.

insert(repo, schema_meta, fields, returning, options)

Specs

insert(repo, schema_meta, fields, returning, options) ::
  {:ok, fields} |
  {:invalid, constraints} |
  no_return

Inserts a single new struct in the data store.

Autogenerate

The primary key will be automatically included in returning if the field has type :id or :binary_id and no value was set by the developer or none was autogenerated by the adapter.

insert_all(repo, schema_meta, header, list, returning, options)

Specs

insert_all(repo, schema_meta, header :: [atom], [fields], returning, options) ::
  {integer, [[term]] | nil} |
  no_return

Inserts multiple entries into the data store.

loaders(primitive_type, ecto_type)

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]
prepare(atom, query)

Specs

prepare(atom :: :all | :update_all | :delete_all, query :: Ecto.Query.t) ::
  {:cache, prepared} |
  {:nocache, prepared}

Commands invoked to prepare a query for all, update_all and delete_all.

The returned result is given to execute/6.

update(repo, schema_meta, fields, filters, returning, options)

Specs

update(repo, schema_meta, fields, filters, returning, options) ::
  {:ok, fields} |
  {:invalid, constraints} |
  {:error, :stale} |
  no_return

Updates a single struct with the given filters.

While filters can be any record column, it is expected that at least the primary key (or any other key that uniquely identifies an existing record) be given as a filter. Therefore, in case there is no record matching the given filters, {:error, :stale} is returned.