Class: ROM::Relation

Inherits:
Object
  • Object
show all
Extended by:
Dry::Core::ClassAttributes, AutoCurry, Initializer, ClassInterface
Includes:
Memoizable, Pipeline, Commands, Materializable
Defined in:
lib/rom/relation.rb,
lib/rom/relation/name.rb,
lib/rom/relation/wrap.rb,
lib/rom/relation/graph.rb,
lib/rom/relation/loaded.rb,
lib/rom/relation/curried.rb,
lib/rom/relation/combined.rb,
lib/rom/relation/commands.rb,
lib/rom/relation/view_dsl.rb,
lib/rom/relation/composite.rb,
lib/rom/relation/materializable.rb,
lib/rom/relation/class_interface.rb

Overview

Base relation class

Relation is a proxy for the dataset object provided by the gateway. It can forward methods to the dataset, which is why the “native” interface of the underlying gateway is available in the relation

Individual adapters sets up their relation classes and provide different APIs depending on their persistence backend.

Direct Known Subclasses

Memory::Relation

Defined Under Namespace

Modules: ClassInterface, Commands, Materializable Classes: Combined, Composite, Curried, Graph, Loaded, Name, ViewDSL, Wrap

Constant Summary collapse

NOOP_OUTPUT_SCHEMA =

Default no-op output schema which is called in ‘Relation#each`

-> tuple { tuple }.freeze

Constants included from ClassInterface

ClassInterface::DEFAULT_DATASET_PROC, ClassInterface::INVALID_RELATIONS_NAMES

Constants included from Memoizable

Memoizable::MEMOIZED_HASH

Instance Attribute Summary collapse

Attributes included from ClassInterface

#relation_name, #schema_proc

Attributes included from Memoizable

#__memoized__

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Initializer

extended

Methods included from ClassInterface

curried, default_name, default_schema, forward, mapper_registry, set_schema!, use, view, view_methods

Methods included from Notifications::Listener

#subscribe

Methods included from AutoCurry

auto_curried_methods, auto_curry, auto_curry_busy?, auto_curry_guard, extended

Methods included from Pipeline::Operator

#>>

Methods included from Materializable

#first, #one, #one!

Methods included from Memoizable

included

Methods included from Commands

#command

Instance Attribute Details

#auto_map ⇒ TrueClass, FalseClass (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Whether or not a relation and its compositions should be auto-mapped.

Returns:

  • (TrueClass, FalseClass) —

    Whether or not a relation and its compositions should be auto-mapped



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# File 'lib/rom/relation.rb', line 166

option :auto_map, default: -> { self.class.auto_map }

#auto_struct ⇒ TrueClass, FalseClass (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Whether or not tuples should be auto-mapped to structs.

Returns:

  • (TrueClass, FalseClass) —

    Whether or not tuples should be auto-mapped to structs



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# File 'lib/rom/relation.rb', line 171

option :auto_struct, default: -> { self.class.auto_struct }

#commands ⇒ CommandRegistry (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Command registry.

Returns:



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# File 'lib/rom/relation.rb', line 185

option :commands, default: -> { CommandRegistry.new({}, relation_name: name.relation) }

#dataset ⇒ Object (readonly)

Returns dataset used by the relation provided by relation’s gateway.

Returns:

  • (Object) —

    dataset used by the relation provided by relation’s gateway



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# File 'lib/rom/relation.rb', line 137

param :dataset

#input_schema ⇒ Object#[] (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns tuple processing function, uses schema or defaults to Hash[].

Returns:

  • (Object#[]) —

    tuple processing function, uses schema or defaults to Hash[]



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# File 'lib/rom/relation.rb', line 154

option :input_schema, default: -> { schema.to_input_hash }

#mappers ⇒ MapperRegistry (readonly)

Returns an optional mapper registry (empty by default).

Returns:



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# File 'lib/rom/relation.rb', line 180

option :mappers, default: -> { self.class.mapper_registry }

#meta ⇒ Hash (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns Meta data stored in a hash.

Returns:

  • (Hash) —

    Meta data stored in a hash



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# File 'lib/rom/relation.rb', line 190

option :meta, reader: true, default: -> { EMPTY_HASH }

#name ⇒ Object (readonly)

Returns The relation name.

Returns:

  • (Object) —

    The relation name



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# File 'lib/rom/relation.rb', line 149

option :name, default: -> { self.class.schema ? self.class.schema.name : self.class.default_name }

#output_schema ⇒ Object#[] (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns tuple processing function, uses schema or defaults to NOOP_OUTPUT_SCHEMA.

Returns:

  • (Object#[]) —

    tuple processing function, uses schema or defaults to NOOP_OUTPUT_SCHEMA



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# File 'lib/rom/relation.rb', line 159

option :output_schema, default: -> {
  schema.any?(&:read?) ? schema.to_output_hash : NOOP_OUTPUT_SCHEMA
}

#schema ⇒ Schema (readonly)

Returns relation schema, defaults to class-level canonical schema (if it was defined) and sets an empty one as the fallback.

Returns:

  • (Schema) —

    relation schema, defaults to class-level canonical schema (if it was defined) and sets an empty one as the fallback



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# File 'lib/rom/relation.rb', line 144

option :schema, default: -> { self.class.schema || self.class.default_schema }

#struct_namespace(ns) ⇒ Relation (readonly)

Return a new relation configured with the provided struct namespace

Parameters:

  • ns (Module) —

    Custom namespace module for auto-structs

Returns:



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# File 'lib/rom/relation.rb', line 176

option :struct_namespace, reader: false, default: -> { self.class.struct_namespace }

Class Method Details

.auto_map ⇒ Boolean .auto_map(value) ⇒ Object

Whether or not a relation and its compositions should be auto-mapped

Overloads:

  • .auto_map ⇒ Boolean

    Return auto_map setting value

    Returns:

    • (Boolean)
  • .auto_map(value) ⇒ Object

    Set auto_map value



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# File 'lib/rom/relation.rb', line 84

defines :auto_map

.auto_struct ⇒ Boolean .auto_struct(value) ⇒ Object

Whether or not tuples should be auto-mapped to structs

Overloads:

  • .auto_struct ⇒ Boolean

    Return auto_struct setting value

    Returns:

    • (Boolean)
  • .auto_struct(value) ⇒ Object

    Set auto_struct value



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# File 'lib/rom/relation.rb', line 95

defines :auto_struct

.gateway ⇒ Symbol .gateway(gateway_key) ⇒ Object

Manage the gateway

Overloads:

  • .gateway ⇒ Symbol

    Return the gateway key that the relation is associated with

    Returns:

    • (Symbol)
  • .gateway(gateway_key) ⇒ Object

    Link the relation to a gateway. Change this setting if the relation is defined on a non-default gateway

    Examples:

    class Users < ROM::Relation[:sql]
  gateway :custom
end

    Parameters:

    • gateway_key (Symbol) 


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# File 'lib/rom/relation.rb', line 73

defines :gateway

.struct_namespace ⇒ Module .struct_namespace(namespace) ⇒ Object

Get or set a namespace for auto-generated struct classes. By default, new struct classes are created within ROM::Struct

@example using custom namespace
  class Users < ROM::Relation[:sql]
    struct_namespace Entities
  end

  users.by_pk(1).one! # => #<Entities::User id=1 name="Jane Doe">

Overloads:

  • .struct_namespace ⇒ Module

    Returns Default struct namespace.

    Returns:

    • (Module) —

      Default struct namespace

  • .struct_namespace(namespace) ⇒ Object

    Parameters:

    • namespace (Module) 


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# File 'lib/rom/relation.rb', line 114

defines :struct_namespace

Instance Method Details

#[](name) ⇒ Attribute

Return schema attribute

Examples:

accessing canonical attribute

users[:id]
# => #<ROM::SQL::Attribute[Integer] primary_key=true name=:id source=ROM::Relation::Name(users)>

accessing joined attribute

tasks_with_users = tasks.join(users).select_append(tasks[:title])
tasks_with_users[:title, :tasks]
# => #<ROM::SQL::Attribute[String] primary_key=false name=:title source=ROM::Relation::Name(tasks)>

Returns:



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# File 'lib/rom/relation.rb', line 206

def [](name)
  schema[name]
end

#adapter ⇒ Symbol

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns The wrapped relation’s adapter identifier ie :sql or :http.

Returns:

  • (Symbol) —

    The wrapped relation’s adapter identifier ie :sql or :http



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# File 'lib/rom/relation.rb', line 562

def adapter
  self.class.adapter
end

#as(aliaz) ⇒ Relation

Return a new relation with an aliased name

Examples:

users.as(:people)

Parameters:

  • aliaz (Symbol) —

    Aliased name

Returns:



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# File 'lib/rom/relation.rb', line 555

def as(aliaz)
  with(name: name.as(aliaz))
end

#associations ⇒ AssociationSet

Return schema’s association set (empty by default)

Returns:



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# File 'lib/rom/relation.rb', line 461

def associations
  schema.associations
end

#attr_ast ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/rom/relation.rb', line 475

def attr_ast
  schema.map { |t| t.to_read_ast }
end

#auto_map? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/rom/relation.rb', line 487

def auto_map?
  (auto_map || auto_struct) && !meta[:combine_type]
end

#auto_struct? ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/rom/relation.rb', line 492

def auto_struct?
  auto_struct && !meta[:combine_type]
end

#call ⇒ Relation::Loaded

Loads a relation

Returns:



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# File 'lib/rom/relation.rb', line 353

def call
  Loaded.new(self)
end

#combine(*associations) ⇒ Relation #combine(*associations, **nested_associations) ⇒ Relation #combine(associations) ⇒ Relation

Combine with other relations using configured associations

Overloads:

  • #combine(*associations) ⇒ Relation

    Examples:

    users.combine(:tasks, :posts)

    Parameters:

    • *associations (Array<Symbol>) —

      A list of association names

  • #combine(*associations, **nested_associations) ⇒ Relation

    Examples:

    users.combine(:tasks, posts: :authors)

    Parameters:

    • *associations (Array<Symbol>) —

      A list of association names

    • *nested_associations (Hash) —

      A hash with nested association names

  • #combine(associations) ⇒ Relation

    Examples:

    users.combine(posts: [:authors, reviews: [:tags, comments: :author])

    Parameters:

    • *associations (Hash) —

      A hash with nested association names

Returns:



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# File 'lib/rom/relation.rb', line 253

def combine(*args)
  combine_with(*nodes(*args))
end

#combine_with(*others) ⇒ Relation::Graph

Composes with other relations

Parameters:

  • others (Array<Relation>) —

    The other relation(s) to compose with

Returns:



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# File 'lib/rom/relation.rb', line 264

def combine_with(*others)
  Combined.new(self, others)
end

#curried? ⇒ false

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns if this relation is curried

Returns:

  • (false) 


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# File 'lib/rom/relation.rb', line 371

def curried?
  false
end

#each {|Hash| ... } ⇒ Enumerator

Yields relation tuples

Every tuple is processed through Relation#output_schema, it’s a no-op by default

Yields:

  • (Hash)

Returns:

  • (Enumerator) —

    if block is not provided



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# File 'lib/rom/relation.rb', line 219

def each
  return to_enum unless block_given?

  if auto_map?
    mapper.(dataset.map { |tuple| output_schema[tuple] }).each { |struct| yield(struct) }
  else
    dataset.each { |tuple| yield(output_schema[tuple]) }
  end
end

#eager_load(assoc) ⇒ Relation

Return a graph node prepared by the given association

Parameters:

  • assoc (Association) —

    An association object

Returns:



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# File 'lib/rom/relation.rb', line 302

def eager_load(assoc)
  relation = assoc.prepare(self)

  if assoc.override?
    relation.(assoc)
  else
    relation.preload_assoc(assoc)
  end
end

#foreign_key(name) ⇒ Symbol

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Return a foreign key name for the provided relation name

Parameters:

  • name (Name) —

    The relation name object

Returns:

  • (Symbol) 


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# File 'lib/rom/relation.rb', line 593

def foreign_key(name)
  attr = schema.foreign_key(name.dataset)

  if attr
    attr.name
  else
    :"#{Inflector.singularize(name.dataset)}_id"
  end
end

#gateway ⇒ Symbol

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Return name of the source gateway of this relation

Returns:

  • (Symbol) 


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# File 'lib/rom/relation.rb', line 571

def gateway
  self.class.gateway
end

#graph? ⇒ false

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns if this relation is a graph

Returns:

  • (false) 


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# File 'lib/rom/relation.rb', line 380

def graph?
  false
end

#map_to(klass, **opts) ⇒ Relation

Return a new relation that will map its tuples to instances of the provided class

Examples:

users.map_to(MyUserModel)

Parameters:

  • klass (Class) —

    Your custom model class

Returns:



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# File 'lib/rom/relation.rb', line 541

def map_to(klass, **opts)
  with(opts.merge(auto_map: false, auto_struct: true, meta: { model: klass }))
end

#map_with(*mappers) ⇒ Relation::Composite #map_with(*mappers, auto_map: true) ⇒ Relation::Composite

Maps relation with custom mappers available in the registry

When auto_map is enabled, your mappers will be applied after performing default auto-mapping. This means that you can compose complex relations and have them auto-mapped, and use much simpler custom mappers to adjust resulting data according to your requirements.

Overloads:

  • #map_with(*mappers) ⇒ Relation::Composite

    Map tuples using registered mappers

    Examples:

    users.map_with(:my_mapper, :my_other_mapper)

    Parameters:

    • mappers (Array<Symbol>) —

      A list of mapper identifiers

  • #map_with(*mappers, auto_map: true) ⇒ Relation::Composite

    Map tuples using custom registered mappers and enforce auto-mapping

    Examples:

    users.map_with(:my_mapper, :my_other_mapper, auto_map: true)

    Parameters:

    • mappers (Array<Symbol>) —

      A list of mapper identifiers

Returns:



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# File 'lib/rom/relation.rb', line 527

def map_with(*names, **opts)
  super(*names).with(opts)
end

#mapper ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/rom/relation.rb', line 497

def mapper
  mappers[to_ast]
end

#meta_ast ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/rom/relation.rb', line 480

def meta_ast
  meta = self.meta.merge(dataset: name.dataset, alias: name.aliaz, struct_namespace: options[:struct_namespace])
  meta[:model] = false unless auto_struct? || meta[:model]
  meta
end

#new(dataset, new_opts = EMPTY_HASH) ⇒ Object

Return a new relation with provided dataset and additional options

Use this method whenever you need to use dataset API to get a new dataset and you want to return a relation back. Typically relation API should be enough though. If you find yourself using this method, it might be worth to consider reporting an issue that some dataset functionality is not available through relation API.

Examples:

with a new dataset

users.new(users.dataset.some_method)

with a new dataset and options

users.new(users.dataset.some_method, other: 'options')

Parameters:

  • dataset (Object)
  • new_opts (Hash) (defaults to: EMPTY_HASH) —

    Additional options



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# File 'lib/rom/relation.rb', line 420

def new(dataset, new_opts = EMPTY_HASH)
  opts =
    if new_opts.empty?
      options
    elsif new_opts.key?(:schema)
      options.merge(new_opts).reject { |k, _| k == :input_schema || k == :output_schema }
    else
      options.merge(new_opts)
    end

  self.class.new(dataset, opts)
end

#node(name) ⇒ Relation

Create a graph node for a given association identifier

Parameters:

Returns:



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# File 'lib/rom/relation.rb', line 289

def node(name)
  assoc = associations[name]
  other = assoc.node
  other.eager_load(assoc)
end

#nodes(*args) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/rom/relation.rb', line 269

def nodes(*args)
  args.reduce([]) do |acc, arg|
    case arg
    when Symbol
      acc << node(arg)
    when Hash
      acc.concat(arg.map { |name, opts| node(name).combine(opts) })
    when Array
      acc.concat(arg.map { |opts| nodes(opts) }.reduce(:concat))
    end
  end
end

#preload_assoc(assoc, other) ⇒ Relation::Curried

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Preload other relation via association

This is used internally when relations are composed

Returns:



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# File 'lib/rom/relation.rb', line 319

def preload_assoc(assoc, other)
  assoc.preload(self, other)
end

#schema? ⇒ TrueClass, FalseClass

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns true if a relation has schema defined

Returns:

  • (TrueClass, FalseClass) 


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# File 'lib/rom/relation.rb', line 398

def schema?
  ! schema.empty?
end

#schemas ⇒ Hash<Symbol=>Schema>

Return all registered relation schemas

This holds all schemas defined via view DSL

Returns:



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# File 'lib/rom/relation.rb', line 582

def schemas
  self.class.schemas
end

#to_a ⇒ Array<Hash>

Materializes a relation into an array

Returns:

  • (Array<Hash>) 


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# File 'lib/rom/relation.rb', line 362

def to_a
  to_enum.to_a
end

#to_ast ⇒ Array

Returns AST for the wrapped relation

Returns:

  • (Array) 


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# File 'lib/rom/relation.rb', line 470

def to_ast
  [:relation, [name.relation, attr_ast, meta_ast]]
end

#with(opts) ⇒ Relation

Returns a new instance with the same dataset but new options

Examples:

users.with(output_schema: -> tuple { .. })

Parameters:

  • opts (Hash) —

    New options

Returns:



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# File 'lib/rom/relation.rb', line 445

def with(opts)
  new_options =
    if opts.key?(:meta)
      opts.merge(meta: meta.merge(opts[:meta]))
    else
      opts
    end

  new(dataset, options.merge(new_options))
end

#wrap(*names) ⇒ Wrap

Wrap other relations using association names

Examples:

tasks.wrap(:owner)

Parameters:

  • names (Array<Symbol>) —

    A list with association identifiers

Returns:



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# File 'lib/rom/relation.rb', line 333

def wrap(*names)
  wrap_around(*names.map { |n| associations[n].wrap })
end

#wrap? ⇒ false

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Return if this is a wrap relation

Returns:

  • (false) 


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# File 'lib/rom/relation.rb', line 389

def wrap?
  false
end

#wrap_around(*others) ⇒ Relation::Wrap

Wrap around other relations

Parameters:

  • others (Array<Relation>) —

    Other relations

Returns:



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# File 'lib/rom/relation.rb', line 344

def wrap_around(*others)
  wrap_class.new(self, others)
end