Active Record Relation
Namespace
Module
Methods
- ==
- any?
- blank?
- build
- cache_key
- create
- create!
- delete_all
- destroy_all
- eager_loading?
- empty?
- encode_with
- explain
- find_or_create_by
- find_or_create_by!
- find_or_initialize_by
- initialize_copy
- inspect
- joined_includes_values
- load
- load_records
- many?
- new
- new
- none?
- one?
- pretty_print
- reload
- reset
- scope_for_create
- scoping
- size
- to_a
- to_ary
- to_sql
- update_all
- values
- where_values_hash
Included Modules
Constants
CLAUSE_METHODS | = | [:where, :having, :from] |
INVALID_METHODS_FOR_DELETE_ALL | = | [:distinct, :group, :having] |
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] |
VALUE_METHODS | = | MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS |
Attributes
[R] | klass | |
[R] | loaded | |
[R] | loaded? | |
[R] | model | |
[R] | predicate_builder | |
[R] | table |
Class Public methods
new(klass, table: klass.arel_table, predicate_builder: klass.predicate_builder, values: {})
π Source code
# File activerecord/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
π See on GitHub
Instance Public methods
==(other)
Compares two relations for equality.
π Source code
# File activerecord/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
π See on GitHub
any?()
Returns true if there are any records.
π Source code
# File activerecord/lib/active_record/relation.rb, line 227
def any?
return super if block_given?
!empty?
end
π See on GitHub
blank?()
Returns true if relation is blank.
π Source code
# File activerecord/lib/active_record/relation.rb, line 503
def blank?
records.blank?
end
π See on GitHub
cache_key(timestamp_column = :updated_at)
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.
π Source code
# File activerecord/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
π See on GitHub
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, ...>
π Source code
# File activerecord/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
π See on GitHub
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!.
π Source code
# File activerecord/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
π See on GitHub
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
π Source code
# File activerecord/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
π See on GitHub
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
π Source code
# File activerecord/lib/active_record/relation.rb, line 364
def destroy_all
records.each(&:destroy).tap { reset }
end
π See on GitHub
eager_loading?()
Returns true if relation needs eager loading.
π Source code
# File activerecord/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
π See on GitHub
empty?()
Returns true if there are no records.
π Source code
# File activerecord/lib/active_record/relation.rb, line 215
def empty?
return @records.empty? if loaded?
!exists?
end
π See on GitHub
encode_with(coder)
Serializes the relation objects Array
.
π Source code
# File activerecord/lib/active_record/relation.rb, line 205
def encode_with(coder)
coder.represent_seq(nil, records)
end
π See on GitHub
explain()
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.
π Source code
# File activerecord/lib/active_record/relation.rb, line 189
def explain
exec_explain(collecting_queries_for_explain { exec_queries })
end
π See on GitHub
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 "PenΓ©lope" or create a new one.
User.find_or_create_by(first_name: 'PenΓ©lope')
# => #<User id: 1, first_name: "PenΓ©lope", last_name: nil>
# Find the first user named "PenΓ©lope" or create a new one.
# We already have one so the existing record will be returned.
User.find_or_create_by(first_name: 'PenΓ©lope')
# => #<User id: 1, first_name: "PenΓ©lope", 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
π Source code
# File activerecord/lib/active_record/relation.rb, line 163
def find_or_create_by(attributes, &block)
find_by(attributes) || create(attributes, &block)
end
π See on GitHub
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.
π Source code
# File activerecord/lib/active_record/relation.rb, line 170
def find_or_create_by!(attributes, &block)
find_by(attributes) || create!(attributes, &block)
end
π See on GitHub
find_or_initialize_by(attributes, &block)
Like find_or_create_by
, but calls new instead of create.
π Source code
# File activerecord/lib/active_record/relation.rb, line 176
def find_or_initialize_by(attributes, &block)
find_by(attributes) || new(attributes, &block)
end
π See on GitHub
initialize_copy(other)
π Source code
# File activerecord/lib/active_record/relation.rb, line 35
def initialize_copy(other)
@values = @values.dup
reset
end
π See on GitHub
inspect()
π Source code
# File activerecord/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
π See on GitHub
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] }
π Source code
# File activerecord/lib/active_record/relation.rb, line 482
def joined_includes_values
includes_values & joins_values
end
π See on GitHub
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>
π Source code
# File activerecord/lib/active_record/relation.rb, line 421
def load(&block)
exec_queries(&block) unless loaded?
self
end
π See on GitHub
many?()
Returns true if there is more than one record.
π Source code
# File activerecord/lib/active_record/relation.rb, line 239
def many?
return super if block_given?
limit_value ? records.many? : size > 1
end
π See on GitHub
new(attributes = nil, &block)
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
π Source code
# File activerecord/lib/active_record/relation.rb, line 56
def new(attributes = nil, &block)
scoping { klass.new(values_for_create(attributes), &block) }
end
π See on GitHub
none?()
Returns true if there are no records.
π Source code
# File activerecord/lib/active_record/relation.rb, line 221
def none?
return super if block_given?
empty?
end
π See on GitHub
one?()
Returns true if there is exactly one record.
π Source code
# File activerecord/lib/active_record/relation.rb, line 233
def one?
return super if block_given?
limit_value ? records.one? : size == 1
end
π See on GitHub
pretty_print(q)
π Source code
# File activerecord/lib/active_record/relation.rb, line 498
def pretty_print(q)
q.pp(records)
end
π See on GitHub
reload()
Forces reloading of relation.
π Source code
# File activerecord/lib/active_record/relation.rb, line 428
def reload
reset
load
end
π See on GitHub
reset()
π Source code
# File activerecord/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
π See on GitHub
scope_for_create()
π Source code
# File activerecord/lib/active_record/relation.rb, line 467
def scope_for_create
where_values_hash.merge!(create_with_value.stringify_keys)
end
π See on GitHub
scoping()
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.
π Source code
# File activerecord/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
π See on GitHub
size()
Returns size of the records.
π Source code
# File activerecord/lib/active_record/relation.rb, line 210
def size
loaded? ? @records.length : count(:all)
end
π See on GitHub
to_ary()
Converts relation objects to Array
.
π Source code
# File activerecord/lib/active_record/relation.rb, line 194
def to_ary
records.dup
end
π See on GitHub
to_sql()
Returns sql statement for the relation.
User.where(name: 'Oscar').to_sql
# => SELECT "users".* FROM "users" WHERE "users"."name" = 'Oscar'
π Source code
# File activerecord/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
π See on GitHub
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.
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')
π Source code
# File activerecord/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
π See on GitHub
values()
π Source code
# File activerecord/lib/active_record/relation.rb, line 507
def values
@values.dup
end
π See on GitHub
where_values_hash(relation_table_name = klass.table_name)
Returns a hash of where conditions.
User.where(name: 'Oscar').where_values_hash
# => {name: "Oscar"}
π Source code
# File activerecord/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
π See on GitHub
Instance Protected methods
load_records(records)
π Source code
# File activerecord/lib/active_record/relation.rb, line 535
def load_records(records)
@records = records.freeze
@loaded = true
end
π See on GitHub