class ActiveRecord::Relation
Active Record Relation¶ ↑
Constants
- CLAUSE_METHODS
- INVALID_METHODS_FOR_DELETE_ALL
- MULTI_VALUE_METHODS
- SINGLE_VALUE_METHODS
- VALUE_METHODS
Attributes
Public Class Methods
# 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 end
Public Instance Methods
Compares two relations for equality.
# File lib/active_record/relation.rb, line 701 def ==(other) case other when Associations::CollectionProxy, AssociationRelation self == other.records when Relation other.to_sql == to_sql when Array records == other end end
Returns true if there are any records.
# File lib/active_record/relation.rb, line 276 def any? return super if block_given? !empty? end
Returns true if relation is blank.
# File lib/active_record/relation.rb, line 717 def blank? records.blank? end
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)
# File lib/active_record/relation.rb, line 310 def cache_key(timestamp_column = "updated_at") @cache_keys ||= {} @cache_keys[timestamp_column] ||= klass.collection_cache_key(self, timestamp_column) end
Returns a cache key along with the version.
# File lib/active_record/relation.rb, line 388 def cache_key_with_version if version = cache_version "#{cache_key}-#{version}" else cache_key end end
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%')
# File lib/active_record/relation.rb, line 337 def cache_version(timestamp_column = :updated_at) if collection_cache_versioning @cache_versions ||= {} @cache_versions[timestamp_column] ||= compute_cache_version(timestamp_column) end end
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, ...>
# File lib/active_record/relation.rb, line 94 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
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!.
# File lib/active_record/relation.rb, line 109 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
Attempts to create a record with the given attributes in a table that has a unique 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 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.
# File lib/active_record/relation.rb, line 208 def create_or_find_by(attributes, &block) transaction(requires_new: true) { create(attributes, &block) } rescue ActiveRecord::RecordNotUnique find_by!(attributes) end
Like create_or_find_by
, but calls create! so an exception is raised if the created record is invalid.
# File lib/active_record/relation.rb, line 217 def create_or_find_by!(attributes, &block) transaction(requires_new: true) { create!(attributes, &block) } rescue ActiveRecord::RecordNotUnique find_by!(attributes) end
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
# File lib/active_record/relation.rb, line 574 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 stmt = Arel::DeleteManager.new stmt.from(arel.source) stmt.key = table[primary_key] stmt.take(arel.limit) stmt.offset(arel.offset) stmt.order(*arel.orders) stmt.wheres = arel.constraints klass.connection.delete(stmt, "#{klass} Destroy").tap { reset } end
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)
# File lib/active_record/relation.rb, line 619 def delete_by(*args) where(*args).delete_all end
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
# File lib/active_record/relation.rb, line 552 def destroy_all records.each(&:destroy).tap { reset } end
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)
# File lib/active_record/relation.rb, line 606 def destroy_by(*args) where(*args).destroy_all end
Returns true if relation needs eager loading.
# File lib/active_record/relation.rb, line 686 def eager_loading? @should_eager_load ||= eager_load_values.any? || includes_values.any? && (joined_includes_values.any? || references_eager_loaded_tables?) end
Returns true if there are no records.
# File lib/active_record/relation.rb, line 264 def empty? return @records.empty? if loaded? !exists? end
Serializes the relation objects Array.
# File lib/active_record/relation.rb, line 254 def encode_with(coder) coder.represent_seq(nil, records) end
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.
# File lib/active_record/relation.rb, line 238 def explain exec_explain(collecting_queries_for_explain { exec_queries }) end
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.
If this might be a problem for your application, please see create_or_find_by
.
# File lib/active_record/relation.rb, line 167 def find_or_create_by(attributes, &block) find_by(attributes) || create(attributes, &block) end
Like find_or_create_by
, but calls create! so an exception is raised if the created record is invalid.
# File lib/active_record/relation.rb, line 174 def find_or_create_by!(attributes, &block) find_by(attributes) || create!(attributes, &block) end
Like find_or_create_by
, but calls new instead of create.
# File lib/active_record/relation.rb, line 225 def find_or_initialize_by(attributes, &block) find_by(attributes) || new(attributes, &block) end
# File lib/active_record/relation.rb, line 36 def initialize_copy(other) @values = @values.dup reset end
# File lib/active_record/relation.rb, line 725 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
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] }
# File lib/active_record/relation.rb, line 696 def joined_includes_values includes_values & joins_values end
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>
# File lib/active_record/relation.rb, line 629 def load(&block) unless loaded? @records = exec_queries(&block) @loaded = true end self end
Returns true if there is more than one record.
# File lib/active_record/relation.rb, line 288 def many? return super if block_given? limit_value ? records.many? : size > 1 end
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
# File lib/active_record/relation.rb, line 69 def new(attributes = nil, &block) block = current_scope_restoring_block(&block) scoping { _new(attributes, &block) } end
Returns true if there are no records.
# File lib/active_record/relation.rb, line 270 def none? return super if block_given? empty? end
Returns true if there is exactly one record.
# File lib/active_record/relation.rb, line 282 def one? return super if block_given? limit_value ? records.one? : size == 1 end
# File lib/active_record/relation.rb, line 712 def pretty_print(q) q.pp(records) end
Forces reloading of relation.
# File lib/active_record/relation.rb, line 639 def reload reset load end
# File lib/active_record/relation.rb, line 644 def reset @delegate_to_klass = false @to_sql = @arel = @loaded = @should_eager_load = nil @offsets = @take = nil @cache_keys = nil @records = [].freeze self end
# File lib/active_record/relation.rb, line 679 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
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.
# File lib/active_record/relation.rb, line 405 def scoping already_in_scope? ? yield : _scoping(self) { yield } end
Returns size of the records.
# File lib/active_record/relation.rb, line 259 def size loaded? ? @records.length : count(:all) end
Converts relation objects to Array.
# File lib/active_record/relation.rb, line 243 def to_ary records.dup end
Returns sql statement for the relation.
User.where(name: 'Oscar').to_sql # => SELECT "users".* FROM "users" WHERE "users"."name" = 'Oscar'
# File lib/active_record/relation.rb, line 657 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
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'"
# File lib/active_record/relation.rb, line 532 def touch_all(*names, time: nil) update_all klass.touch_attributes_with_time(*names, time: time) end
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')
# File lib/active_record/relation.rb, line 440 def update_all(updates) raise ArgumentError, "Empty list of attributes to change" if updates.blank? arel = eager_loading? ? apply_join_dependency.arel : build_arel arel.source.left = table stmt = Arel::UpdateManager.new stmt.table(arel.source) stmt.key = table[primary_key] stmt.take(arel.limit) stmt.offset(arel.offset) stmt.order(*arel.orders) stmt.wheres = arel.constraints 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 stmt.set _substitute_values(updates) else stmt.set Arel.sql(klass.sanitize_sql_for_assignment(updates, table.name)) end klass.connection.update(stmt, "#{klass} Update All").tap { reset } end
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)
# File lib/active_record/relation.rb, line 489 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
# File lib/active_record/relation.rb, line 721 def values @values.dup end
Returns a hash of where conditions.
User.where(name: 'Oscar').where_values_hash # => {name: "Oscar"}
# File lib/active_record/relation.rb, line 675 def where_values_hash(relation_table_name = klass.table_name) where_clause.to_h(relation_table_name) end
Protected Instance Methods
# File lib/active_record/relation.rb, line 768 def load_records(records) @records = records.freeze @loaded = true end
Private Instance Methods
# File lib/active_record/relation.rb, line 794 def _create(attributes, &block) klass.create(attributes, &block) end
# File lib/active_record/relation.rb, line 798 def _create!(attributes, &block) klass.create!(attributes, &block) end
# File lib/active_record/relation.rb, line 820 def _increment_attribute(attribute, value = 1) bind = predicate_builder.build_bind_attribute(attribute.name, value.abs) expr = table.coalesce(Arel::Nodes::UnqualifiedColumn.new(attribute), 0) expr = value < 0 ? expr - bind : expr + bind expr.expr end
# File lib/active_record/relation.rb, line 790 def _new(attributes, &block) klass.new(attributes, &block) end
# File lib/active_record/relation.rb, line 802 def _scoping(scope) previous, klass.current_scope = klass.current_scope(true), scope yield ensure klass.current_scope = previous end
# File lib/active_record/relation.rb, line 809 def _substitute_values(values) values.map do |name, value| attr = table[name] unless Arel.arel_node?(value) type = klass.type_for_attribute(attr.name) value = predicate_builder.build_bind_attribute(attr.name, type.cast(value)) end [attr, value] end end
# File lib/active_record/relation.rb, line 778 def already_in_scope? @delegate_to_klass && klass.current_scope(true) end
# File lib/active_record/relation.rb, line 865 def build_preloader ActiveRecord::Associations::Preloader.new end
# File lib/active_record/relation.rb, line 782 def current_scope_restoring_block(&block) current_scope = klass.current_scope(true) -> record do klass.current_scope = current_scope yield record if block_given? end end
# File lib/active_record/relation.rb, line 827 def exec_queries(&block) skip_query_cache_if_necessary do records = if where_clause.contradiction? [] elsif eager_loading? apply_join_dependency do |relation, join_dependency| if relation.null_relation? [] else relation = join_dependency.apply_column_aliases(relation) rows = connection.select_all(relation.arel, "SQL") join_dependency.instantiate(rows, strict_loading_value, &block) end.freeze end else klass.find_by_sql(arel, &block).freeze end preload_associations(records) unless skip_preloading_value records.each(&:readonly!) if readonly_value records.each(&:strict_loading!) if strict_loading_value records end end
# File lib/active_record/relation.rb, line 869 def references_eager_loaded_tables? joined_tables = build_joins([]).flat_map do |join| if join.is_a?(Arel::Nodes::StringJoin) tables_in_string(join.left) else join.left.name end end joined_tables << table.name # always convert table names to downcase as in Oracle quoted table names are in uppercase joined_tables.map!(&:downcase) !(references_values.map(&:to_s) - joined_tables).empty? end
# File lib/active_record/relation.rb, line 855 def skip_query_cache_if_necessary if skip_query_cache_value uncached do yield end else yield end end
# File lib/active_record/relation.rb, line 886 def tables_in_string(string) return [] if string.blank? # always convert table names to downcase as in Oracle quoted table names are in uppercase # ignore raw_sql_ that is used by Oracle adapter as alias for limit/offset subqueries string.scan(/[a-zA-Z_][.\w]+(?=.?\.)/).map!(&:downcase) - ["raw_sql_"] end