Class: ActiveRecord::Relation

Inherits:
Object
  • Object
show all
Includes:
Batches, Calculations, Delegation, Explain, FinderMethods, QueryMethods, RecordFetchWarning, 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,
lib/active_record/relation/where_clause_factory.rb

Overview

Active Record Relation

Defined Under Namespace

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

Constant Summary collapse

MULTI_VALUE_METHODS = 
[:includes, :eager_load, :preload, :select, :group,
:order, :joins, :left_outer_joins, :references,
:extending, :unscope]
SINGLE_VALUE_METHODS = 
[:limit, :offset, :lock, :readonly, :reordering,
:reverse_order, :distinct, :create_with, :skip_query_cache]
CLAUSE_METHODS = 
[:where, :having, :from]
INVALID_METHODS_FOR_DELETE_ALL = 
[:distinct, :group, :having]
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!, #first, #first!, #forty_two, #forty_two!, #fourth, #fourth!, #last, #last!, #raise_record_not_found_exception!, #second, #second!, #second_to_last, #second_to_last!, #take, #take!, #third, #third!, #third_to_last, #third_to_last!

Methods included from Calculations

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

Methods included from SpawnMethods

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

Methods included from QueryMethods

#_select!, #arel, #create_with, #create_with!, #distinct, #distinct!, #eager_load, #eager_load!, #extending, #extending!, #from, #from!, #get_value, #group, #group!, #having, #having!, #includes, #includes!, #joins, #joins!, #left_outer_joins, #left_outer_joins!, #limit, #limit!, #lock, #lock!, #none, #none!, #offset, #offset!, #or, #or!, #order, #order!, #preload, #preload!, #readonly, #readonly!, #references, #references!, #reorder, #reorder!, #reverse_order, #reverse_order!, #rewhere, #select, #skip_query_cache!, #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 25

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

Instance Attribute Details

#klass ⇒ Object (readonly) Also known as: model

Returns the value of attribute klass.



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# File 'lib/active_record/relation.rb', line 20

def klass
  @klass
end

#loaded ⇒ Object (readonly) Also known as: loaded?

Returns the value of attribute loaded.



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# File 'lib/active_record/relation.rb', line 20

def loaded
  @loaded
end

#predicate_builder ⇒ Object (readonly)

Returns the value of attribute predicate_builder.



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# File 'lib/active_record/relation.rb', line 20

def predicate_builder
  @predicate_builder
end

#table ⇒ Object (readonly)

Returns the value of attribute table.



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# File 'lib/active_record/relation.rb', line 20

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 487

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_scope(*args, &block) ⇒ Object

:nodoc:



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# File 'lib/active_record/relation.rb', line 286

def _exec_scope(*args, &block) # :nodoc:
  @delegate_to_klass = true
  instance_exec(*args, &block) || 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 528

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

#any? ⇒ Boolean

Returns true if there are any records.

Returns:

  • (Boolean) 


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# File 'lib/active_record/relation.rb', line 227

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

#arel_attribute(name) ⇒ Object

:nodoc:



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# File 'lib/active_record/relation.rb', line 40

def arel_attribute(name) # :nodoc:
  klass.arel_attribute(name, table)
end

#blank? ⇒ Boolean

Returns true if relation is blank.

Returns:

  • (Boolean) 


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# File 'lib/active_record/relation.rb', line 503

def blank?
  records.blank?
end

#cache_key(timestamp_column = :updated_at) ⇒ Object

Returns a cache key that can be used to identify the records fetched by this query. The cache key is built with a fingerprint of the sql query, the number of records matched by the query and a 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 key changes.

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

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%')

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)

You can customize the strategy to generate the key on a per model basis overriding ActiveRecord::Base#collection_cache_key.



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# File 'lib/active_record/relation.rb', line 265

def cache_key(timestamp_column = :updated_at)
  @cache_keys ||= {}
  @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column)
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 81

def create(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr, &block) }
  else
    scoping { klass.create(values_for_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 95

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

#delete_all ⇒ Object

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 386

def delete_all
  invalid_methods = INVALID_METHODS_FOR_DELETE_ALL.select do |method|
    value = get_value(method)
    SINGLE_VALUE_METHODS.include?(method) ? value : value.any?
  end
  if invalid_methods.any?
    raise ActiveRecordError.new("delete_all doesn't support #{invalid_methods.join(', ')}")
  end

  if eager_loading?
    relation = apply_join_dependency
    return relation.delete_all
  end

  stmt = Arel::DeleteManager.new
  stmt.from(table)

  if has_join_values? || has_limit_or_offset?
    @klass.connection.join_to_delete(stmt, arel, arel_attribute(primary_key))
  else
    stmt.wheres = arel.constraints
  end

  affected = @klass.connection.delete(stmt, "#{@klass} Destroy")

  reset
  affected
end

#destroy_all ⇒ Object

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 364

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

#eager_loading? ⇒ Boolean

Returns true if relation needs eager loading.

Returns:

  • (Boolean) 


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# File 'lib/active_record/relation.rb', line 472

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 215

def empty?
  return @records.empty? if loaded?
  !exists?
end

#empty_scope? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/active_record/relation.rb', line 520

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 205

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

#explain ⇒ Object

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 189

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
# different 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.

Whether that is a problem or not depends on the logic of the application, but in the particular case in which rows have a UNIQUE constraint an exception may be raised, just retry:

begin
  CreditAccount.transaction(requires_new: true) do
    CreditAccount.find_or_create_by(user_id: user.id)
  end
rescue ActiveRecord::RecordNotUnique
  retry
end



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# File 'lib/active_record/relation.rb', line 163

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 170

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 176

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 103

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 107

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 111

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 524

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 35

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

#inspect ⇒ Object 



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# File 'lib/active_record/relation.rb', line 511

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

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

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

#joined_includes_values ⇒ Object

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 482

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 421

def load(&block)
  exec_queries(&block) unless loaded?

  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 239

def many?
  return super if block_given?
  limit_value ? records.many? : size > 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 56

def new(attributes = nil, &block)
  scoping { klass.new(values_for_create(attributes), &block) }
end

#none? ⇒ Boolean

Returns true if there are no records.

Returns:

  • (Boolean) 


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# File 'lib/active_record/relation.rb', line 221

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 233

def one?
  return super if block_given?
  limit_value ? records.one? : size == 1
end

#pretty_print(q) ⇒ Object 



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# File 'lib/active_record/relation.rb', line 498

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

#records ⇒ Object

:nodoc:



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# File 'lib/active_record/relation.rb', line 199

def records # :nodoc:
  load
  @records
end

#reload ⇒ Object

Forces reloading of relation.



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# File 'lib/active_record/relation.rb', line 428

def reload
  reset
  load
end

#reset ⇒ Object 



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# File 'lib/active_record/relation.rb', line 433

def reset
  @delegate_to_klass = false
  @to_sql = @arel = @loaded = @should_eager_load = nil
  @records = [].freeze
  @offsets = {}
  self
end

#scope_for_create ⇒ Object 



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# File 'lib/active_record/relation.rb', line 467

def scope_for_create
  where_values_hash.merge!(create_with_value.stringify_keys)
end

#scoping ⇒ 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

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 279

def scoping
  previous, klass.current_scope = klass.current_scope(true), self unless @delegate_to_klass
  yield
ensure
  klass.current_scope = previous unless @delegate_to_klass
end

#size ⇒ Object

Returns size of the records.



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# File 'lib/active_record/relation.rb', line 210

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

#to_ary ⇒ Object Also known as: to_a

Converts relation objects to Array.



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# File 'lib/active_record/relation.rb', line 194

def to_ary
  records.dup
end

#to_sql ⇒ Object

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 445

def to_sql
  @to_sql ||= begin
    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
end

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

:nodoc:



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# File 'lib/active_record/relation.rb', line 340

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.

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 315

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

  if eager_loading?
    relation = apply_join_dependency
    return relation.update_all(updates)
  end

  stmt = Arel::UpdateManager.new

  stmt.set Arel.sql(@klass.sanitize_sql_for_assignment(updates))
  stmt.table(table)

  if has_join_values? || offset_value
    @klass.connection.join_to_update(stmt, arel, arel_attribute(primary_key))
  else
    stmt.key = arel_attribute(primary_key)
    stmt.take(arel.limit)
    stmt.order(*arel.orders)
    stmt.wheres = arel.constraints
  end

  @klass.connection.update stmt, "#{@klass} Update All"
end

#values ⇒ Object 



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# File 'lib/active_record/relation.rb', line 507

def values
  @values.dup
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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464
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# File 'lib/active_record/relation.rb', line 463

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