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Class: ActiveRecord::Relation

Constant Summary

Batches - Included

DEFAULT_ORDER, ORDER_IGNORE_MESSAGE

QueryMethods - Included

FROZEN_EMPTY_ARRAY, FROZEN_EMPTY_HASH, VALID_UNSCOPING_VALUES

FinderMethods - Included

ONE_AS_ONE

Class Method Summary

Instance Attribute Summary

::Enumerable - Included

#many?

Returns true if the enumerable has more than 1 element.

Instance Method Summary

FinderMethods - Included

#exists?

Returns true if a record exists in the table that matches the id or conditions given, or false otherwise.

#fifth

Find the fifth record.

#fifth!

Same as #fifth but raises RecordNotFound if no record is found.

#find

Find by id - This can either be a specific id (ID), a list of ids (ID, ID, ID), or an array of ids ([ID, ID, ID]).

#find_by

Finds the first record matching the specified conditions.

#find_by!

Like #find_by, except that if no record is found, raises an RecordNotFound error.

#find_sole_by

Finds the sole matching record.

#first

Find the first record (or first N records if a parameter is supplied).

#first!

Same as #first but raises RecordNotFound if no record is found.

#forty_two

Find the forty-second record.

#forty_two!

Same as #forty_two but raises RecordNotFound if no record is found.

#fourth

Find the fourth record.

#fourth!

Same as #fourth but raises RecordNotFound if no record is found.

#include?

Returns true if the relation contains the given record or false otherwise.

#last

Find the last record (or last N records if a parameter is supplied).

#last!

Same as #last but raises RecordNotFound if no record is found.

#member?
#second

Find the second record.

#second!

Same as #second but raises RecordNotFound if no record is found.

#second_to_last

Find the second-to-last record.

#second_to_last!

Same as #second_to_last but raises RecordNotFound if no record is found.

#sole

Finds the sole matching record.

#take

Gives a record (or N records if a parameter is supplied) without any implied order.

#take!

Same as #take but raises RecordNotFound if no record is found.

#third

Find the third record.

#third!

Same as #third but raises RecordNotFound if no record is found.

#third_to_last

Find the third-to-last record.

#third_to_last!

Same as #third_to_last but raises RecordNotFound if no record is found.

Calculations - Included

#async_average

Same as #average, but performs the query asynchronously and returns an Promise.

#async_count

Same as #count, but performs the query asynchronously and returns an Promise.

#async_ids

Same as #ids, but performs the query asynchronously and returns an Promise.

#async_maximum

Same as #maximum, but performs the query asynchronously and returns an Promise.

#async_minimum

Same as #minimum, but performs the query asynchronously and returns an Promise.

#async_pick

Same as #pick, but performs the query asynchronously and returns an Promise.

#async_pluck

Same as #pluck, but performs the query asynchronously and returns an Promise.

#async_sum

Same as #sum, but performs the query asynchronously and returns an Promise.

#average

Calculates the average value on a given column.

#calculate

This calculates aggregate values in the given column.

#count

Count the records.

#ids

Returns the base model’s ID’s for the relation using the table’s primary key.

#maximum

Calculates the maximum value on a given column.

#minimum

Calculates the minimum value on a given column.

#pick

Pick the value(s) from the named column(s) in the current relation.

#pluck

Use #pluck as a shortcut to select one or more attributes without loading an entire record object per row.

#sum

Calculates the sum of values on a given column.

SpawnMethods - Included

#except

Removes from the query the condition(s) specified in skips.

#merge

Merges in the conditions from other, if other is an Relation.

#only

Removes any condition from the query other than the one(s) specified in onlies.

QueryMethods - Included

#and

Returns a new relation, which is the logical intersection of this relation and the one passed as an argument.

#annotate

Adds an SQL comment to queries generated from this relation.

#create_with

Sets attributes to be used when creating new records from a relation object.

#distinct

Specifies whether the records should be unique or not.

#eager_load

Specify associations args to be eager loaded using a LEFT OUTER JOIN.

#excluding

Excludes the specified record (or collection of records) from the resulting relation.

#extending

Used to extend a scope with additional methods, either through a module or through a block provided.

#extensions,
#extract_associated

Extracts a named association from the relation.

#from

Specifies the table from which the records will be fetched.

#group

Allows to specify a group attribute:

#having

Allows to specify a HAVING clause.

#in_order_of

Allows to specify an order by a specific set of values.

#includes

Specify associations args to be eager loaded to prevent N + 1 queries.

#invert_where

Allows you to invert an entire where clause instead of manually applying conditions.

#joins

Performs JOINs on args.

#left_joins
#left_outer_joins

Performs LEFT OUTER JOINs on args:

#limit

Specifies a limit for the number of records to retrieve.

#lock

Specifies locking settings (default to true).

#none

Returns a chainable relation with zero records.

#offset

Specifies the number of rows to skip before returning rows.

#optimizer_hints

Specify optimizer hints to be used in the SELECT statement.

#or

Returns a new relation, which is the logical union of this relation and the one passed as an argument.

#order

Applies an ORDER BY clause to a query.

#preload

Specify associations args to be eager loaded using separate queries.

#readonly

Mark a relation as readonly.

#references

Use to indicate that the given table_names are referenced by an SQL string, and should therefore be JOINed in any query rather than loaded separately.

#regroup

Allows you to change a previously set group statement.

#reorder

Replaces any existing order defined on the relation with the specified order.

#reselect

Allows you to change a previously set select statement.

#reverse_order

Reverse the existing order clause on the relation.

#rewhere

Allows you to change a previously set where condition for a given attribute, instead of appending to that condition.

#select

Works in two unique ways.

#strict_loading

Sets the returned relation to strict_loading mode.

#structurally_compatible?

Checks whether the given relation is structurally compatible with this relation, to determine if it’s possible to use the #and and #or methods without raising an error.

#uniq!

Deduplicate multiple values.

#unscope

Removes an unwanted relation that is already defined on a chain of relations.

#where

Returns a new relation, which is the result of filtering the current relation according to the conditions in the arguments.

#with

Add a Common Table Expression (CTE) that you can then reference within another SELECT statement.

#without

Batches - Included

#find_each

Looping through a collection of records from the database (using the Scoping::Named::ClassMethods#all method, for example) is very inefficient since it will try to instantiate all the objects at once.

#find_in_batches

Yields each batch of records that was found by the find options as an array.

#in_batches

Yields Relation objects to work with a batch of records.

::Enumerable - Included

#compact_blank

Returns a new ::Array without the blank items.

#exclude?

The negative of the Enumerable#include?.

#excluding

Returns a copy of the enumerable excluding the specified elements.

#in_order_of

Returns a new ::Array where the order has been set to that provided in the series, based on the key of the objects in the original enumerable.

#including

Returns a new array that includes the passed elements.

#index_by

Convert an enumerable to a hash, using the block result as the key and the element as the value.

#index_with

Convert an enumerable to a hash, using the element as the key and the block result as the value.

#maximum

Calculates the maximum from the extracted elements.

#minimum

Calculates the minimum from the extracted elements.

#pick

Extract the given key from the first element in the enumerable.

#pluck

Extract the given key from each element in the enumerable.

#sole

Returns the sole item in the enumerable.

#without

Constructor Details

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

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 28

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
  @async = false
  @none = false
end

Instance Attribute Details

#blank?Boolean (readonly)

Returns true if relation is blank.

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# File 'activerecord/lib/active_record/relation.rb', line 844

def blank?
  records.blank?
end

#eager_loading?Boolean (readonly)

Returns true if relation needs eager loading.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 808

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

#empty?Boolean (readonly)

Returns true if there are no records.

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# File 'activerecord/lib/active_record/relation.rb', line 283

def empty?
  return true if @none

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

#klass (readonly) Also known as: #model

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

attr_reader :table, :klass, :loaded, :predicate_builder

#loaded? (readonly)

Alias for #loaded.

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# File 'activerecord/lib/active_record/relation.rb', line 25

alias :loaded? :loaded

#many?Boolean (readonly)

Returns true if there is more than one record.

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# File 'activerecord/lib/active_record/relation.rb', line 334

def many?
  return false if @none

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

#model (readonly)

Alias for #klass.

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# File 'activerecord/lib/active_record/relation.rb', line 24

alias :model :klass

#predicate_builder (readonly)

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

attr_reader :table, :klass, :loaded, :predicate_builder

#scheduled?Boolean (readonly)

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

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# File 'activerecord/lib/active_record/relation.rb', line 740

def scheduled?
  !!@future_result
end

#skip_preloading_value (rw)

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# File 'activerecord/lib/active_record/relation.rb', line 23

attr_accessor :skip_preloading_value

#table (readonly)

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

attr_reader :table, :klass, :loaded, :predicate_builder

Instance Method Details

#==(other)

Compares two relations for equality.

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# File 'activerecord/lib/active_record/relation.rb', line 823

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

#any?(*args) ⇒ Boolean

Returns true if there are any records.

When a pattern argument is given, this method checks whether elements in the ::Enumerable match the pattern via the case-equality operator (===).

posts.any?(Post) # => true or false
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# File 'activerecord/lib/active_record/relation.rb', line 312

def any?(*args)
  return false if @none

  return super if args.present? || block_given?
  !empty?
end

#build(attributes = nil, &block)

Alias for #new.

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# File 'activerecord/lib/active_record/relation.rb', line 77

alias build new

#cache_key(timestamp_column = "updated_at")

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 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 'activerecord/lib/active_record/relation.rb', line 359

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

#cache_key_with_version

Returns a cache key along with the version.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 438

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

#cache_version(timestamp_column = :updated_at)

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%')
[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 386

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)

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, ...>
[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 98

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)

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!}.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 113

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)

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 tries to create the record first. As such it is better suited for cases where the record is most likely not to exist yet.

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.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 215

def create_or_find_by(attributes, &block)
  transaction(requires_new: true) { create(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
  if connection.transaction_open?
    where(attributes).lock.find_by!(attributes)
  else
    find_by!(attributes)
  end
end

#create_or_find_by!(attributes, &block)

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

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 228

def create_or_find_by!(attributes, &block)
  transaction(requires_new: true) { create!(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
  if connection.transaction_open?
    where(attributes).lock.find_by!(attributes)
  else
    find_by!(attributes)
  end
end

#delete_all

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
[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 651

def delete_all
  return 0 if @none

  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?
  key = if klass.composite_primary_key?
    primary_key.map { |pk| table[pk] }
  else
    table[primary_key]
  end
  stmt = arel.compile_delete(key, having_clause_ast, group_values_arel_columns)

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

#delete_by(*args)

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)
[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 699

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

#destroy_all

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
[ GitHub ]

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

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

#destroy_by(*args)

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)
[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 686

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

#encode_with(coder)

Serializes the relation objects ::Array.

[ GitHub ]

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

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

#explain(*options)

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.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 253

def explain(*options)
  exec_explain(collecting_queries_for_explain { exec_queries }, options)
end

#find_or_create_by(attributes, &block)

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.

If creation failed because of a unique constraint, this method will assume it encountered a race condition and will try finding the record once more. If somehow the second find still does not find a record because a concurrent DELETE happened, it will then raise an RecordNotFound exception.

Please note this method is not atomic, it runs first a SELECT, and if there are no results an INSERT is attempted. So if the table doesn’t have a relevant unique constraint it could be the case that you end up with two or more similar records.

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

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

#find_or_create_by!(attributes, &block)

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

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 182

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

#find_or_initialize_by(attributes, &block)

Like #find_or_create_by, but calls new instead of create.

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 240

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

#initialize_copy(other)

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# File 'activerecord/lib/active_record/relation.rb', line 41

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

#inspect

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# File 'activerecord/lib/active_record/relation.rb', line 856

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_values

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] }

[ GitHub ]

  
# File 'activerecord/lib/active_record/relation.rb', line 818

def joined_includes_values
  includes_values & joins_values
end

#load(&block)

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>
[ GitHub ]

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

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

  self
end

#load_async

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 'activerecord/lib/active_record/relation.rb', line 721

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

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

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

attr_reader :table, :klass, :loaded, :predicate_builder

#locked?

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# File 'activerecord/lib/active_record/relation.rb', line 26

alias :locked? :lock_value

#new(attributes = nil, &block) 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 'activerecord/lib/active_record/relation.rb', line 69

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?(*args) ⇒ Boolean

Returns true if there are no records.

When a pattern argument is given, this method checks whether elements in the ::Enumerable match the pattern via the case-equality operator (===).

posts.none?(Comment) # => true or false
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# File 'activerecord/lib/active_record/relation.rb', line 299

def none?(*args)
  return true if @none

  return super if args.present? || block_given?
  empty?
end

#one?(*args) ⇒ Boolean

Returns true if there is exactly one record.

When a pattern argument is given, this method checks whether elements in the ::Enumerable match the pattern via the case-equality operator (===).

posts.one?(Post) # => true or false
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# File 'activerecord/lib/active_record/relation.rb', line 325

def one?(*args)
  return false if @none

  return super if args.present? || block_given?
  return records.one? if loaded?
  limited_count == 1
end

#pretty_print(pp)

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# File 'activerecord/lib/active_record/relation.rb', line 834

def pretty_print(pp)
  subject = loaded? ? records : annotate("loading for pp")
  entries = subject.take([limit_value, 11].compact.min)

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

  pp.pp(entries)
end

#reload

Forces reloading of relation.

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

def reload
  reset
  load
end

#reset

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

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
  @cache_versions = nil
  @records = nil
  self
end

#scope_for_create

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# File 'activerecord/lib/active_record/relation.rb', line 801

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)

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 'activerecord/lib/active_record/relation.rb', line 460

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

#size

Returns size of the records.

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# File 'activerecord/lib/active_record/relation.rb', line 274

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

#to_a

Alias for #to_ary.

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# File 'activerecord/lib/active_record/relation.rb', line 261

alias to_a to_ary

#to_ary Also known as: #to_a

Converts relation objects to ::Array.

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# File 'activerecord/lib/active_record/relation.rb', line 258

def to_ary
  records.dup
end

#to_sql

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 'activerecord/lib/active_record/relation.rb', line 781

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)

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 'activerecord/lib/active_record/relation.rb', line 609

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

#update_all(updates)

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. Any strings provided will be type cast, unless you use Arel.sql. (Don’t pass user-provided values to Arel.sql.)

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')

# Update all books with 'Rails' in their title
Book.where('title LIKE ?', '%Rails%').update_all(title: Arel.sql("title + ' - volume 1'"))

Raises:

  • (ArgumentError)
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# File 'activerecord/lib/active_record/relation.rb', line 507

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

  return 0 if @none

  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?
  key = if klass.composite_primary_key?
    primary_key.map { |pk| table[pk] }
  else
    table[primary_key]
  end
  stmt = arel.compile_update(values, key, having_clause_ast, group_values_arel_columns)
  klass.connection.update(stmt, "#{klass} Update All").tap { reset }
end

#update_counters(counters)

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 'activerecord/lib/active_record/relation.rb', line 566

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

#values

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# File 'activerecord/lib/active_record/relation.rb', line 848

def values
  @values.dup
end