Class: ActiveRecord::Relation

Inherits:
Object
  • Object
show all
Includes:
Batches, Calculations, Delegation, Explain, FinderMethods, QueryMethods, SpawnMethods, Enumerable
Defined in:
lib/active_record/relation.rb,
lib/active_record/relation/merger.rb,
lib/active_record/relation/from_clause.rb,
lib/active_record/relation/where_clause.rb,
lib/active_record/relation/query_attribute.rb,
lib/active_record/relation/record_fetch_warning.rb

Overview

Active Record Relation

Defined Under Namespace

Modules: RecordFetchWarning Classes: FromClause, HashMerger, Merger, QueryAttribute, StrictLoadingScope, WhereClause

Constant Summary collapse

MULTI_VALUE_METHODS =
[:includes, :eager_load, :preload, :select, :group,
:order, :joins, :left_outer_joins, :references,
:extending, :unscope, :optimizer_hints, :annotate]
SINGLE_VALUE_METHODS =
[:limit, :offset, :lock, :readonly, :reordering, :strict_loading,
:reverse_order, :distinct, :create_with, :skip_query_cache]
CLAUSE_METHODS =
[:where, :having, :from]
INVALID_METHODS_FOR_DELETE_ALL =
[:distinct]
VALUE_METHODS =
MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS

Constants included from FinderMethods

FinderMethods::ONE_AS_ONE

Constants included from QueryMethods

QueryMethods::FROZEN_EMPTY_ARRAY, QueryMethods::FROZEN_EMPTY_HASH, QueryMethods::VALID_UNSCOPING_VALUES

Constants included from Batches

Batches::ORDER_IGNORE_MESSAGE

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from FinderMethods

#exists?, #fifth, #fifth!, #find, #find_by, #find_by!, #find_sole_by, #first, #first!, #forty_two, #forty_two!, #fourth, #fourth!, #include?, #last, #last!, #raise_record_not_found_exception!, #second, #second!, #second_to_last, #second_to_last!, #sole, #take, #take!, #third, #third!, #third_to_last, #third_to_last!

Methods included from Calculations

#average, #calculate, #count, #ids, #maximum, #minimum, #pick, #pluck, #sum

Methods included from SpawnMethods

#except, #merge, #merge!, #only, #spawn

Methods included from QueryMethods

#_select!, #and, #and!, #annotate, #annotate!, #arel, #construct_join_dependency, #create_with, #create_with!, #distinct, #distinct!, #eager_load, #eager_load!, #excluding, #excluding!, #extending, #extending!, #extract_associated, #from, #from!, #group, #group!, #having, #having!, #in_order_of, #includes, #includes!, #invert_where, #invert_where!, #joins, #joins!, #left_outer_joins, #left_outer_joins!, #limit, #limit!, #lock, #lock!, #none, #none!, #offset, #offset!, #optimizer_hints, #optimizer_hints!, #or, #or!, #order, #order!, #preload, #preload!, #readonly, #readonly!, #references, #references!, #reorder, #reorder!, #reselect, #reselect!, #reverse_order, #reverse_order!, #rewhere, #select, #skip_preloading!, #skip_query_cache!, #strict_loading, #strict_loading!, #structurally_compatible?, #uniq!, #unscope, #unscope!, #where, #where!

Methods included from Batches

#find_each, #find_in_batches, #in_batches

Methods included from Explain

#collecting_queries_for_explain, #exec_explain

Constructor Details

#initialize(klass, table: klass.arel_table, predicate_builder: klass.predicate_builder, values: {}) ⇒ Relation

Returns a new instance of Relation.


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# File 'lib/active_record/relation.rb', line 27

def initialize(klass, table: klass.arel_table, predicate_builder: klass.predicate_builder, values: {})
  @klass  = klass
  @table  = table
  @values = values
  @loaded = false
  @predicate_builder = predicate_builder
  @delegate_to_klass = false
  @future_result = nil
  @records = nil
end

Instance Attribute Details

#klassObject (readonly) Also known as: model

Returns the value of attribute klass.


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# File 'lib/active_record/relation.rb', line 21

def klass
  @klass
end

#loadedObject (readonly) Also known as: loaded?

Returns the value of attribute loaded.


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# File 'lib/active_record/relation.rb', line 21

def loaded
  @loaded
end

#predicate_builderObject (readonly)

Returns the value of attribute predicate_builder.


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# File 'lib/active_record/relation.rb', line 21

def predicate_builder
  @predicate_builder
end

#skip_preloading_valueObject

Returns the value of attribute skip_preloading_value.


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# File 'lib/active_record/relation.rb', line 22

def skip_preloading_value
  @skip_preloading_value
end

#tableObject (readonly)

Returns the value of attribute table.


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# File 'lib/active_record/relation.rb', line 21

def table
  @table
end

Instance Method Details

#==(other) ⇒ Object

Compares two relations for equality.


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# File 'lib/active_record/relation.rb', line 765

def ==(other)
  case other
  when Associations::CollectionProxy, AssociationRelation
    self == other.records
  when Relation
    other.to_sql == to_sql
  when Array
    records == other
  end
end

#_exec_scopeObject

:nodoc:


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# File 'lib/active_record/relation.rb', line 432

def _exec_scope(...) # :nodoc:
  @delegate_to_klass = true
  registry = klass.scope_registry
  _scoping(nil, registry) { instance_exec(...) || self }
ensure
  @delegate_to_klass = false
end

#alias_tracker(joins = [], aliases = nil) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 810

def alias_tracker(joins = [], aliases = nil) # :nodoc:
  ActiveRecord::Associations::AliasTracker.create(connection, table.name, joins, aliases)
end

#any?Boolean

Returns true if there are any records.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 284

def any?
  return super if block_given?
  !empty?
end

#bind_attribute(name, value) {|attr, bind| ... } ⇒ Object

:nodoc:

Yields:

  • (attr, bind)

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# File 'lib/active_record/relation.rb', line 43

def bind_attribute(name, value) # :nodoc:
  if reflection = klass._reflect_on_association(name)
    name = reflection.foreign_key
    value = value.read_attribute(reflection.klass.primary_key) unless value.nil?
  end

  attr = table[name]
  bind = predicate_builder.build_bind_attribute(attr.name, value)
  yield attr, bind
end

#blank?Boolean

Returns true if relation is blank.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 781

def blank?
  records.blank?
end

#cache_key(timestamp_column = "updated_at") ⇒ Object

Returns a stable cache key that can be used to identify this query. The cache key is built with a fingerprint of the SQL query.

Product.where("name like ?", "%Cosmic Encounter%").cache_key
# => "products/query-1850ab3d302391b85b8693e941286659"

If ActiveRecord::Base.collection_cache_versioning is turned off, as it was in Rails 6.0 and earlier, the cache key will also include a version.

ActiveRecord::Base.collection_cache_versioning = false
Product.where("name like ?", "%Cosmic Encounter%").cache_key
# => "products/query-1850ab3d302391b85b8693e941286659-1-20150714212553907087000"

You can also pass a custom timestamp column to fetch the timestamp of the last updated record.

Product.where("name like ?", "%Game%").cache_key(:last_reviewed_at)

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# File 'lib/active_record/relation.rb', line 320

def cache_key(timestamp_column = "updated_at")
  @cache_keys ||= {}
  @cache_keys[timestamp_column] ||= klass.collection_cache_key(self, timestamp_column)
end

#cache_key_with_versionObject

Returns a cache key along with the version.


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# File 'lib/active_record/relation.rb', line 399

def cache_key_with_version
  if version = cache_version
    "#{cache_key}-#{version}"
  else
    cache_key
  end
end

#cache_version(timestamp_column = :updated_at) ⇒ Object

Returns a cache version that can be used together with the cache key to form a recyclable caching scheme. The cache version is built with the number of records matching the query, and the timestamp of the last updated record. When a new record comes to match the query, or any of the existing records is updated or deleted, the cache version changes.

If the collection is loaded, the method will iterate through the records to generate the timestamp, otherwise it will trigger one SQL query like:

SELECT COUNT(*), MAX("products"."updated_at") FROM "products" WHERE (name like '%Cosmic Encounter%')

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# File 'lib/active_record/relation.rb', line 347

def cache_version(timestamp_column = :updated_at)
  if collection_cache_versioning
    @cache_versions ||= {}
    @cache_versions[timestamp_column] ||= compute_cache_version(timestamp_column)
  end
end

#create(attributes = nil, &block) ⇒ Object

Tries to create a new record with the same scoped attributes defined in the relation. Returns the initialized object if validation fails.

Expects arguments in the same format as ActiveRecord::Base.create.

Examples

users = User.where(name: 'Oscar')
users.create # => #<User id: 3, name: "Oscar", ...>

users.create(name: 'fxn')
users.create # => #<User id: 4, name: "fxn", ...>

users.create { |user| user.name = 'tenderlove' }
# => #<User id: 5, name: "tenderlove", ...>

users.create(name: nil) # validation on name
# => #<User id: nil, name: nil, ...>

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

def create(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr, &block) }
  else
    block = current_scope_restoring_block(&block)
    scoping { _create(attributes, &block) }
  end
end

#create!(attributes = nil, &block) ⇒ Object

Similar to #create, but calls create! on the base class. Raises an exception if a validation error occurs.

Expects arguments in the same format as ActiveRecord::Base.create!.


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# File 'lib/active_record/relation.rb', line 110

def create!(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create!(attr, &block) }
  else
    block = current_scope_restoring_block(&block)
    scoping { _create!(attributes, &block) }
  end
end

#create_or_find_by(attributes, &block) ⇒ Object

Attempts to create a record with the given attributes in a table that has a unique database constraint on one or several of its columns. If a row already exists with one or several of these unique constraints, the exception such an insertion would normally raise is caught, and the existing record with those attributes is found using #find_by!.

This is similar to #find_or_create_by, but avoids the problem of stale reads between the SELECT and the INSERT, as that method needs to first query the table, then attempt to insert a row if none is found.

There are several drawbacks to #create_or_find_by, though:

  • The underlying table must have the relevant columns defined with unique database constraints.

  • A unique constraint violation may be triggered by only one, or at least less than all, of the given attributes. This means that the subsequent #find_by! may fail to find a matching record, which will then raise an ActiveRecord::RecordNotFound exception, rather than a record with the given attributes.

  • While we avoid the race condition between SELECT -> INSERT from #find_or_create_by, we actually have another race condition between INSERT -> SELECT, which can be triggered if a DELETE between those two statements is run by another client. But for most applications, that's a significantly less likely condition to hit.

  • It relies on exception handling to handle control flow, which may be marginally slower.

  • The primary key may auto-increment on each create, even if it fails. This can accelerate the problem of running out of integers, if the underlying table is still stuck on a primary key of type int (note: All Rails apps since 5.1+ have defaulted to bigint, which is not liable to this problem).

This method will return a record if all given attributes are covered by unique constraints (unless the INSERT -> DELETE -> SELECT race condition is triggered), but if creation was attempted and failed due to validation errors it won't be persisted, you get what #create returns in such situation.


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# File 'lib/active_record/relation.rb', line 209

def create_or_find_by(attributes, &block)
  transaction(requires_new: true) { create(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
  find_by!(attributes)
end

#create_or_find_by!(attributes, &block) ⇒ Object

Like #create_or_find_by, but calls create! so an exception is raised if the created record is invalid.


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# File 'lib/active_record/relation.rb', line 218

def create_or_find_by!(attributes, &block)
  transaction(requires_new: true) { create!(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
  find_by!(attributes)
end

#delete_allObject

Deletes the records without instantiating the records first, and hence not calling the #destroy method nor invoking callbacks. This is a single SQL DELETE statement that goes straight to the database, much more efficient than #destroy_all. Be careful with relations though, in particular :dependent rules defined on associations are not honored. Returns the number of rows affected.

Post.where(person_id: 5).where(category: ['Something', 'Else']).delete_all

Both calls delete the affected posts all at once with a single DELETE statement. If you need to destroy dependent associations or call your before_* or after_destroy callbacks, use the #destroy_all method instead.

If an invalid method is supplied, #delete_all raises an ActiveRecordError:

Post.distinct.delete_all
# => ActiveRecord::ActiveRecordError: delete_all doesn't support distinct

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# File 'lib/active_record/relation.rb', line 601

def delete_all
  invalid_methods = INVALID_METHODS_FOR_DELETE_ALL.select do |method|
    value = @values[method]
    method == :distinct ? value : value&.any?
  end
  if invalid_methods.any?
    raise ActiveRecordError.new("delete_all doesn't support #{invalid_methods.join(', ')}")
  end

  arel = eager_loading? ? apply_join_dependency.arel : build_arel
  arel.source.left = table

  group_values_arel_columns = arel_columns(group_values.uniq)
  having_clause_ast = having_clause.ast unless having_clause.empty?
  stmt = arel.compile_delete(table[primary_key], having_clause_ast, group_values_arel_columns)

  klass.connection.delete(stmt, "#{klass} Delete All").tap { reset }
end

#delete_by(*args) ⇒ Object

Finds and deletes all records matching the specified conditions. This is short-hand for relation.where(condition).delete_all. Returns the number of rows affected.

If no record is found, returns 0 as zero rows were affected.

Person.delete_by(id: 13)
Person.delete_by(name: 'Spartacus', rating: 4)
Person.delete_by("published_at < ?", 2.weeks.ago)

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# File 'lib/active_record/relation.rb', line 642

def delete_by(*args)
  where(*args).delete_all
end

#destroy_allObject

Destroys the records by instantiating each record and calling its #destroy method. Each object's callbacks are executed (including :dependent association options). Returns the collection of objects that were destroyed; each will be frozen, to reflect that no changes should be made (since they can't be persisted).

Note: Instantiation, callback execution, and deletion of each record can be time consuming when you're removing many records at once. It generates at least one SQL DELETE query per record (or possibly more, to enforce your callbacks). If you want to delete many rows quickly, without concern for their associations or callbacks, use #delete_all instead.

Examples

Person.where(age: 0..18).destroy_all

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# File 'lib/active_record/relation.rb', line 579

def destroy_all
  records.each(&:destroy).tap { reset }
end

#destroy_by(*args) ⇒ Object

Finds and destroys all records matching the specified conditions. This is short-hand for relation.where(condition).destroy_all. Returns the collection of objects that were destroyed.

If no record is found, returns empty array.

Person.destroy_by(id: 13)
Person.destroy_by(name: 'Spartacus', rating: 4)
Person.destroy_by("published_at < ?", 2.weeks.ago)

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# File 'lib/active_record/relation.rb', line 629

def destroy_by(*args)
  where(*args).destroy_all
end

#eager_loading?Boolean

Returns true if relation needs eager loading.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 750

def eager_loading?
  @should_eager_load ||=
    eager_load_values.any? ||
    includes_values.any? && (joined_includes_values.any? || references_eager_loaded_tables?)
end

#empty?Boolean

Returns true if there are no records.

Returns:

  • (Boolean)

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

def empty?
  if loaded?
    records.empty?
  else
    !exists?
  end
end

#empty_scope?Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 802

def empty_scope? # :nodoc:
  @values == klass.unscoped.values
end

#encode_with(coder) ⇒ Object

Serializes the relation objects Array.


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# File 'lib/active_record/relation.rb', line 255

def encode_with(coder)
  coder.represent_seq(nil, records)
end

#explainObject

Runs EXPLAIN on the query or queries triggered by this relation and returns the result as a string. The string is formatted imitating the ones printed by the database shell.

Note that this method actually runs the queries, since the results of some are needed by the next ones when eager loading is going on.

Please see further details in the Active Record Query Interface guide.


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# File 'lib/active_record/relation.rb', line 239

def explain
  exec_explain(collecting_queries_for_explain { exec_queries })
end

#find_or_create_by(attributes, &block) ⇒ Object

Finds the first record with the given attributes, or creates a record with the attributes if one is not found:

# Find the first user named "Penélope" or create a new one.
User.find_or_create_by(first_name: 'Penélope')
# => #<User id: 1, first_name: "Penélope", last_name: nil>

# Find the first user named "Penélope" or create a new one.
# We already have one so the existing record will be returned.
User.find_or_create_by(first_name: 'Penélope')
# => #<User id: 1, first_name: "Penélope", last_name: nil>

# Find the first user named "Scarlett" or create a new one with
# a particular last name.
User.create_with(last_name: 'Johansson').find_or_create_by(first_name: 'Scarlett')
# => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">

This method accepts a block, which is passed down to #create. The last example above can be alternatively written this way:

# Find the first user named "Scarlett" or create a new one with a
# particular last name.
User.find_or_create_by(first_name: 'Scarlett') do |user|
  user.last_name = 'Johansson'
end
# => #<User id: 2, first_name: "Scarlett", last_name: "Johansson">

This method always returns a record, but if creation was attempted and failed due to validation errors it won't be persisted, you get what #create returns in such situation.

Please note this method is not atomic, it runs first a SELECT, and if there are no results an INSERT is attempted. If there are other threads or processes there is a race condition between both calls and it could be the case that you end up with two similar records.

If this might be a problem for your application, please see #create_or_find_by.


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# File 'lib/active_record/relation.rb', line 168

def find_or_create_by(attributes, &block)
  find_by(attributes) || create(attributes, &block)
end

#find_or_create_by!(attributes, &block) ⇒ Object

Like #find_or_create_by, but calls create! so an exception is raised if the created record is invalid.


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# File 'lib/active_record/relation.rb', line 175

def find_or_create_by!(attributes, &block)
  find_by(attributes) || create!(attributes, &block)
end

#find_or_initialize_by(attributes, &block) ⇒ Object

Like #find_or_create_by, but calls new instead of create.


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# File 'lib/active_record/relation.rb', line 226

def find_or_initialize_by(attributes, &block)
  find_by(attributes) || new(attributes, &block)
end

#first_or_create(attributes = nil, &block) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 119

def first_or_create(attributes = nil, &block) # :nodoc:
  first || create(attributes, &block)
end

#first_or_create!(attributes = nil, &block) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 123

def first_or_create!(attributes = nil, &block) # :nodoc:
  first || create!(attributes, &block)
end

#first_or_initialize(attributes = nil, &block) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 127

def first_or_initialize(attributes = nil, &block) # :nodoc:
  first || new(attributes, &block)
end

#has_limit_or_offset?Boolean

:nodoc:

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 806

def has_limit_or_offset? # :nodoc:
  limit_value || offset_value
end

#initialize_copy(other) ⇒ Object


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# File 'lib/active_record/relation.rb', line 38

def initialize_copy(other)
  @values = @values.dup
  reset
end

#inspectObject


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# File 'lib/active_record/relation.rb', line 793

def inspect
  subject = loaded? ? records : annotate("loading for inspect")
  entries = subject.take([limit_value, 11].compact.min).map!(&:inspect)

  entries[10] = "..." if entries.size == 11

  "#<#{self.class.name} [#{entries.join(', ')}]>"
end

#joined_includes_valuesObject

Joins that are also marked for preloading. In which case we should just eager load them. Note that this is a naive implementation because we could have strings and symbols which represent the same association, but that aren't matched by this. Also, we could have nested hashes which partially match, e.g. { a: :b } & { a: [:b, :c] }


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# File 'lib/active_record/relation.rb', line 760

def joined_includes_values
  includes_values & joins_values
end

#load(&block) ⇒ Object

Causes the records to be loaded from the database if they have not been loaded already. You can use this if for some reason you need to explicitly load some records before actually using them. The return value is the relation itself, not the records.

Post.where(published: true).load # => #<ActiveRecord::Relation>

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# File 'lib/active_record/relation.rb', line 693

def load(&block)
  if !loaded? || scheduled?
    @records = exec_queries(&block)
    @loaded = true
  end

  self
end

#load_asyncObject

Schedule the query to be performed from a background thread pool.

Post.where(published: true).load_async # => #<ActiveRecord::Relation>

When the Relation is iterated, if the background query wasn't executed yet, it will be performed by the foreground thread.

Note that config.active_record.async_query_executor must be configured for queries to actually be executed concurrently. Otherwise it defaults to executing them in the foreground.

load_async will also fall back to executing in the foreground in the test environment when transactional fixtures are enabled.

If the query was actually executed in the background, the Active Record logs will show it by prefixing the log line with ASYNC:

ASYNC Post Load (0.0ms) (db time 2ms)  SELECT "posts".* FROM "posts" LIMIT 100

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# File 'lib/active_record/relation.rb', line 664

def load_async
  return load if !connection.async_enabled?

  unless loaded?
    result = exec_main_query(async: connection.current_transaction.closed?)

    if result.is_a?(Array)
      @records = result
    else
      @future_result = result
    end
    @loaded = true
  end

  self
end

#many?Boolean

Returns true if there is more than one record.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 297

def many?
  return super if block_given?
  return records.many? if loaded?
  limited_count > 1
end

#new(attributes = nil, &block) ⇒ Object Also known as: build

Initializes new record from relation while maintaining the current scope.

Expects arguments in the same format as ActiveRecord::Base.new.

users = User.where(name: 'DHH')
user = users.new # => #<User id: nil, name: "DHH", created_at: nil, updated_at: nil>

You can also pass a block to new with the new record as argument:

user = users.new { |user| user.name = 'Oscar' }
user.name # => Oscar

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# File 'lib/active_record/relation.rb', line 66

def new(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| new(attr, &block) }
  else
    block = current_scope_restoring_block(&block)
    scoping { _new(attributes, &block) }
  end
end

#none?Boolean

Returns true if there are no records.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 278

def none?
  return super if block_given?
  empty?
end

#one?Boolean

Returns true if there is exactly one record.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 290

def one?
  return super if block_given?
  return records.one? if loaded?
  limited_count == 1
end

#preload_associations(records) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 824

def preload_associations(records) # :nodoc:
  preload = preload_values
  preload += includes_values unless eager_loading?
  scope = strict_loading_value ? StrictLoadingScope : nil
  preload.each do |associations|
    ActiveRecord::Associations::Preloader.new(records: records, associations: associations, scope: scope).call
  end
end

#pretty_print(q) ⇒ Object


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# File 'lib/active_record/relation.rb', line 776

def pretty_print(q)
  q.pp(records)
end

#recordsObject

:nodoc:


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# File 'lib/active_record/relation.rb', line 249

def records # :nodoc:
  load
  @records
end

#reloadObject

Forces reloading of relation.


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# File 'lib/active_record/relation.rb', line 703

def reload
  reset
  load
end

#resetObject


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# File 'lib/active_record/relation.rb', line 708

def reset
  @future_result&.cancel
  @future_result = nil
  @delegate_to_klass = false
  @to_sql = @arel = @loaded = @should_eager_load = nil
  @offsets = @take = nil
  @cache_keys = nil
  @records = nil
  self
end

#scheduled?Boolean

Returns true if the relation was scheduled on the background thread pool.

Returns:

  • (Boolean)

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# File 'lib/active_record/relation.rb', line 683

def scheduled?
  !!@future_result
end

#scope_for_createObject


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# File 'lib/active_record/relation.rb', line 743

def scope_for_create
  hash = where_clause.to_h(klass.table_name, equality_only: true)
  create_with_value.each { |k, v| hash[k.to_s] = v } unless create_with_value.empty?
  hash
end

#scoping(all_queries: nil, &block) ⇒ Object

Scope all queries to the current scope.

Comment.where(post_id: 1).scoping do
  Comment.first
end
# => SELECT "comments".* FROM "comments" WHERE "comments"."post_id" = 1 ORDER BY "comments"."id" ASC LIMIT 1

If all_queries: true is passed, scoping will apply to all queries for the relation including update and delete on instances. Once all_queries is set to true it cannot be set to false in a nested block.

Please check unscoped if you want to remove all previous scopes (including the default_scope) during the execution of a block.


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# File 'lib/active_record/relation.rb', line 421

def scoping(all_queries: nil, &block)
  registry = klass.scope_registry
  if global_scope?(registry) && all_queries == false
    raise ArgumentError, "Scoping is set to apply to all queries and cannot be unset in a nested block."
  elsif already_in_scope?(registry)
    yield
  else
    _scoping(self, registry, all_queries, &block)
  end
end

#sizeObject

Returns size of the records.


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# File 'lib/active_record/relation.rb', line 260

def size
  if loaded?
    records.length
  else
    count(:all)
  end
end

#to_aryObject Also known as: to_a

Converts relation objects to Array.


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# File 'lib/active_record/relation.rb', line 244

def to_ary
  records.dup
end

#to_sqlObject

Returns sql statement for the relation.

User.where(name: 'Oscar').to_sql
# => SELECT "users".* FROM "users"  WHERE "users"."name" = 'Oscar'

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# File 'lib/active_record/relation.rb', line 723

def to_sql
  @to_sql ||= if eager_loading?
    apply_join_dependency do |relation, join_dependency|
      relation = join_dependency.apply_column_aliases(relation)
      relation.to_sql
    end
  else
    conn = klass.connection
    conn.unprepared_statement { conn.to_sql(arel) }
  end
end

#touch_all(*names, time: nil) ⇒ Object

Touches all records in the current relation, setting the updated_at/updated_on attributes to the current time or the time specified. It does not instantiate the involved models, and it does not trigger Active Record callbacks or validations. This method can be passed attribute names and an optional time argument. If attribute names are passed, they are updated along with updated_at/updated_on attributes. If no time argument is passed, the current time is used as default.

Examples

# Touch all records
Person.all.touch_all
# => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670'"

# Touch multiple records with a custom attribute
Person.all.touch_all(:created_at)
# => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670', \"created_at\" = '2018-01-04 22:55:23.132670'"

# Touch multiple records with a specified time
Person.all.touch_all(time: Time.new(2020, 5, 16, 0, 0, 0))
# => "UPDATE \"people\" SET \"updated_at\" = '2020-05-16 00:00:00'"

# Touch records with scope
Person.where(name: 'David').touch_all
# => "UPDATE \"people\" SET \"updated_at\" = '2018-01-04 22:55:23.132670' WHERE \"people\".\"name\" = 'David'"

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# File 'lib/active_record/relation.rb', line 559

def touch_all(*names, time: nil)
  update_all klass.touch_attributes_with_time(*names, time: time)
end

#update(id = :all, attributes) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 488

def update(id = :all, attributes) # :nodoc:
  if id == :all
    each { |record| record.update(attributes) }
  else
    klass.update(id, attributes)
  end
end

#update!(id = :all, attributes) ⇒ Object

:nodoc:


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# File 'lib/active_record/relation.rb', line 496

def update!(id = :all, attributes) # :nodoc:
  if id == :all
    each { |record| record.update!(attributes) }
  else
    klass.update!(id, attributes)
  end
end

#update_all(updates) ⇒ Object

Updates all records in the current relation with details given. This method constructs a single SQL UPDATE statement and sends it straight to the database. It does not instantiate the involved models and it does not trigger Active Record callbacks or validations. However, values passed to #update_all will still go through Active Record's normal type casting and serialization. Returns the number of rows affected.

Note: As Active Record callbacks are not triggered, this method will not automatically update updated_at/updated_on columns.

Parameters

  • updates - A string, array, or hash representing the SET part of an SQL statement.

Examples

# Update all customers with the given attributes
Customer.update_all wants_email: true

# Update all books with 'Rails' in their title
Book.where('title LIKE ?', '%Rails%').update_all(author: 'David')

# Update all books that match conditions, but limit it to 5 ordered by date
Book.where('title LIKE ?', '%Rails%').order(:created_at).limit(5).update_all(author: 'David')

# Update all invoices and set the number column to its id value.
Invoice.update_all('number = id')

Raises:

  • (ArgumentError)

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# File 'lib/active_record/relation.rb', line 464

def update_all(updates)
  raise ArgumentError, "Empty list of attributes to change" if updates.blank?

  if updates.is_a?(Hash)
    if klass.locking_enabled? &&
        !updates.key?(klass.locking_column) &&
        !updates.key?(klass.locking_column.to_sym)
      attr = table[klass.locking_column]
      updates[attr.name] = _increment_attribute(attr)
    end
    values = _substitute_values(updates)
  else
    values = Arel.sql(klass.sanitize_sql_for_assignment(updates, table.name))
  end

  arel = eager_loading? ? apply_join_dependency.arel : build_arel
  arel.source.left = table

  group_values_arel_columns = arel_columns(group_values.uniq)
  having_clause_ast = having_clause.ast unless having_clause.empty?
  stmt = arel.compile_update(values, table[primary_key], having_clause_ast, group_values_arel_columns)
  klass.connection.update(stmt, "#{klass} Update All").tap { reset }
end

#update_counters(counters) ⇒ Object

Updates the counters of the records in the current relation.

Parameters

  • counter - A Hash containing the names of the fields to update as keys and the amount to update as values.

  • :touch option - Touch the timestamp columns when updating.

  • If attributes names are passed, they are updated along with update_at/on attributes.

Examples

# For Posts by a given author increment the comment_count by 1.
Post.where(author_id: author.id).update_counters(comment_count: 1)

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# File 'lib/active_record/relation.rb', line 516

def update_counters(counters)
  touch = counters.delete(:touch)

  updates = {}
  counters.each do |counter_name, value|
    attr = table[counter_name]
    updates[attr.name] = _increment_attribute(attr, value)
  end

  if touch
    names = touch if touch != true
    names = Array.wrap(names)
    options = names.extract_options!
    touch_updates = klass.touch_attributes_with_time(*names, **options)
    updates.merge!(touch_updates) unless touch_updates.empty?
  end

  update_all updates
end

#valuesObject


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# File 'lib/active_record/relation.rb', line 785

def values
  @values.dup
end

#values_for_queriesObject

:nodoc:


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# File 'lib/active_record/relation.rb', line 789

def values_for_queries # :nodoc:
  @values.except(:extending, :skip_query_cache, :strict_loading)
end

#where_values_hash(relation_table_name = klass.table_name) ⇒ Object

Returns a hash of where conditions.

User.where(name: 'Oscar').where_values_hash
# => {name: "Oscar"}

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# File 'lib/active_record/relation.rb', line 739

def where_values_hash(relation_table_name = klass.table_name) # :nodoc:
  where_clause.to_h(relation_table_name)
end