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 24 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
Public Instance Methods
Compares two relations for equality.
# File lib/active_record/relation.rb, line 480 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 226 def any? return super if block_given? !empty? end
Returns true if relation is blank.
# File lib/active_record/relation.rb, line 496 def blank? records.blank? end
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.
# File lib/active_record/relation.rb, line 264 def cache_key(timestamp_column = :updated_at) @cache_keys ||= {} @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column) 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 80 def create(attributes = nil, &block) if attributes.is_a?(Array) attributes.collect { |attr| create(attr, &block) } else scoping { klass.create(scope_for_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 94 def create!(attributes = nil, &block) if attributes.is_a?(Array) attributes.collect { |attr| create!(attr, &block) } else scoping { klass.create!(scope_for_create(attributes), &block) } end 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 377 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
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 355 def destroy_all records.each(&:destroy).tap { reset } end
Returns true if relation needs eager loading.
# File lib/active_record/relation.rb, line 465 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 214 def empty? return @records.empty? if loaded? !exists? end
Serializes the relation objects Array.
# File lib/active_record/relation.rb, line 204 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 188 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.
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
# File lib/active_record/relation.rb, line 162 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 169 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 175 def find_or_initialize_by(attributes, &block) find_by(attributes) || new(attributes, &block) end
# File lib/active_record/relation.rb, line 34 def initialize_copy(other) @values = @values.dup reset end
# File lib/active_record/relation.rb, line 504 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
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 475 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 412 def load(&block) exec_queries(&block) unless loaded? self end
Returns true if there is more than one record.
# File lib/active_record/relation.rb, line 238 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 55 def new(attributes = nil, &block) scoping { klass.new(scope_for_create(attributes), &block) } end
Returns true if there are no records.
# File lib/active_record/relation.rb, line 220 def none? return super if block_given? empty? end
Returns true if there is exactly one record.
# File lib/active_record/relation.rb, line 232 def one? return super if block_given? limit_value ? records.one? : size == 1 end
# File lib/active_record/relation.rb, line 491 def pretty_print(q) q.pp(records) end
Forces reloading of relation.
# File lib/active_record/relation.rb, line 419 def reload reset load end
# File lib/active_record/relation.rb, line 424 def reset @delegate_to_klass = false @to_sql = @arel = @loaded = @should_eager_load = nil @records = [].freeze @offsets = {} self end
# File lib/active_record/relation.rb, line 458 def scope_for_create(attributes = nil) scope = where_values_hash.merge!(create_with_value.stringify_keys) scope.merge!(attributes) if attributes scope 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 278 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
Returns size of the records.
# File lib/active_record/relation.rb, line 209 def size loaded? ? @records.length : count(:all) end
Converts relation objects to Array.
# File lib/active_record/relation.rb, line 193 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 436 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
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')
# File lib/active_record/relation.rb, line 314 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
# File lib/active_record/relation.rb, line 500 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 454 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 528 def load_records(records) @records = records.freeze @loaded = true end
Private Instance Methods
# File lib/active_record/relation.rb, line 581 def build_preloader ActiveRecord::Associations::Preloader.new end
# File lib/active_record/relation.rb, line 539 def exec_queries(&block) skip_query_cache_if_necessary do @records = if eager_loading? apply_join_dependency do |relation, join_dependency| if ActiveRecord::NullRelation === relation [] else relation = join_dependency.apply_column_aliases(relation) rows = connection.select_all(relation.arel, "SQL") join_dependency.instantiate(rows, &block) end.freeze end else klass.find_by_sql(arel, &block).freeze end preload = preload_values preload += includes_values unless eager_loading? preloader = nil preload.each do |associations| preloader ||= build_preloader preloader.preload @records, associations end @records.each(&:readonly!) if readonly_value @loaded = true @records end end
# File lib/active_record/relation.rb, line 535 def has_join_values? joins_values.any? || left_outer_joins_values.any? end
# File lib/active_record/relation.rb, line 585 def references_eager_loaded_tables? joined_tables = arel.join_sources.map do |join| if join.is_a?(Arel::Nodes::StringJoin) tables_in_string(join.left) else [join.left.table_name, join.left.table_alias] end end joined_tables += [table.name, table.table_alias] # always convert table names to downcase as in Oracle quoted table names are in uppercase joined_tables = joined_tables.flatten.compact.map(&:downcase).uniq (references_values - joined_tables).any? end
# File lib/active_record/relation.rb, line 571 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 602 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]+).?\./).flatten.map(&:downcase).uniq - ["raw_sql_"] end