Phoenix API Toolkit v0.3.0 PhoenixApiToolkit.Ecto.DynamicFilters View Source

Dynamic filtering of Ecto queries is useful for creating list/index functions, and ultimately list/index endpoints, that accept a map of filters to apply to the query. Such a map can be based on HTTP query parameters, naturally.

This module complements PhoenixApiToolkit.Ecto.GenericQueries by leveraging the generic queries provided by that module to filter a query dynamically based on a parameter map.

Several filtering types are so common that they have been implemented using standard filter macro's. This way, you only have to define which fields are filterable in what way.

Example without standard filters

def list_without_standard_filters(filters \\ %{}) do
  from(user in "users", as: :user)
  |> apply_filters(filters, fn
    {:order_by, {field, direction}}, query ->
      GenericQueries.order_by(query, :user, field, direction)

    {literal, value}, query when literal in [:id, :name, :residence, :address] ->
      GenericQueries.equals(query, :user, literal, value)

    _, query ->
      query
  end)
end

# filtering is optional
iex> list_without_standard_filters()
#Ecto.Query<from u0 in "users", as: :user>

# multiple literal matches can be combined
iex> list_without_standard_filters(%{residence: "New York", address: "Main Street"})
#Ecto.Query<from u0 in "users", as: :user, where: u0.address == ^"Main Street", where: u0.residence == ^"New York">

# literal matches and sorting can be combined
iex> list_without_standard_filters(%{residence: "New York", order_by: {:name, :desc}})
#Ecto.Query<from u0 in "users", as: :user, where: u0.residence == ^"New York", order_by: [desc: u0.name]>

# other fields are ignored / passed through
iex> list_without_standard_filters(%{number_of_arms: 3})
#Ecto.Query<from u0 in "users", as: :user>

Example with standard filters

Standard filters can be applied using the standard_filters/4 macro. It supports various filtering styles: literal matches, set membership, smaller/greater than comparisons, ordering and pagination. These filters must be configured at compile time.

@filter_definitions [
  literals: [:id, :username, :address, :balance],
  sets: [:roles],
  smaller_than: [
    inserted_before: :inserted_at,
    balance_sm: :balance
  ],
  greater_than_or_equals: [
    inserted_at_or_after: :inserted_at,
    balance_gte: :balance
  ]
]

def by_username_prefix(query, prefix) do
  from(user in query, where: ilike(user.username, ^"#{prefix}%"))
end

def list_with_standard_filters(filters \\ %{}) do
  from(user in "users", as: :user)
  |> apply_filters(filters, fn
    # Add custom filters first and fallback to standard filters
    {:username_prefix, value}, query -> by_username_prefix(query, value)
    filter, query -> standard_filters(query, filter, :user, @filter_definitions)
  end)
end

# filtering is optional
iex> list_with_standard_filters()
#Ecto.Query<from u0 in "users", as: :user>

# let's do some filtering
iex> list_with_standard_filters(%{username: "Peter", balance_sm: 50.00})
#Ecto.Query<from u0 in "users", as: :user, where: u0.balance < ^50.0, where: u0.username == ^"Peter">

# limit, offset, and order_by are supported
iex> list_with_standard_filters(%{limit: 10, offset: 1, order_by: {:address, :desc}})
#Ecto.Query<from u0 in "users", as: :user, order_by: [desc: u0.address], limit: ^10, offset: ^1>

# complex custom filters can be combined with the standard filters
iex> list_with_standard_filters(%{username_prefix: "Pete", balance_gte: 50.00})
#Ecto.Query<from u0 in "users", as: :user, where: u0.balance >= ^50.0, where: ilike(u0.username, ^"Pete%")>

# other fields are ignored / passed through
iex> list_with_standard_filters(%{number_of_arms: 3, order_by: {:boom, :asc}})
#Ecto.Query<from u0 in "users", as: :user>

Link to this section Summary

Types

Format of a filter that can be applied to a query to narrow it down

Filter definitions supported by standard_filters/4. A keyword list of filter types and the fields for which they should be generated.

Functions

Applies filters to query by reducing filters using filter_reductor. Combine with the generic queries from PhoenixApiToolkit.Ecto.GenericQueries to write complex filterables. Several standard filters have been implemented in standard_filters/4.

Applies standard filters to the query. Standard filters include filters for literal matches, set membership, smaller/greater than comparisons, ordering and pagination.

Link to this section Types

Link to this type

filter()

View Source
filter() :: {atom(), any()}

Format of a filter that can be applied to a query to narrow it down

Link to this type

filter_definitions()

View Source
filter_definitions() :: [
  literals: [atom()],
  sets: [atom()],
  smaller_than: keyword(atom()),
  greater_than_or_equals: keyword(atom())
]

Filter definitions supported by standard_filters/4. A keyword list of filter types and the fields for which they should be generated.

Link to this section Functions

Link to this function

apply_filters(query, filters, filter_reductor)

View Source
apply_filters(Query.t(), map(), (Query.t(), filter() -> Query.t())) ::
  Query.t()

Applies filters to query by reducing filters using filter_reductor. Combine with the generic queries from PhoenixApiToolkit.Ecto.GenericQueries to write complex filterables. Several standard filters have been implemented in standard_filters/4.

See the module docs Elixir.PhoenixApiToolkit.Ecto.DynamicFilters for details and examples.

Link to this macro

standard_filters(query, filter, main_binding, filter_definitions)

View Source (macro)
standard_filters(Query.t(), filter(), atom(), filter_definitions()) :: any()

Applies standard filters to the query. Standard filters include filters for literal matches, set membership, smaller/greater than comparisons, ordering and pagination.

See the module docs Elixir.PhoenixApiToolkit.Ecto.DynamicFilters for details and examples.

Mandatory parameters:

  • query: the Ecto query that is narrowed down
  • filter: the current filter that is being applied to query
  • main_binding: the named binding of the Ecto model that generic queries are applied to
  • filter_definitions: keyword list of filter types and the fields for which they should be generated

The options supported by the filter_definitions parameter are: