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rails--rails/activerecord/lib/active_record/relation.rb
Daniel Colson 6928950def Avoid passing unnecessary arguments to relation 
Most of the time the table and predicate_builder
passed to Relation.new are exactly the
arel_table and predicate builder of the
given klass. This uses klass.arel_table
and klass.predicate_builder as the defaults,
so we don't have to pass them in most cases.

This does change the signaure of both Relation and
AssocationRelation. Are we ok with that?
2018-01-24 16:49:35 -05:00

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# frozen_string_literal: true
module ActiveRecord
# = Active Record \Relation
class Relation
MULTI_VALUE_METHODS = [:includes, :eager_load, :preload, :select, :group,
:order, :joins, :left_outer_joins, :references,
:extending, :unscope]
SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
:reverse_order, :distinct, :create_with, :skip_query_cache]
CLAUSE_METHODS = [:where, :having, :from]
INVALID_METHODS_FOR_DELETE_ALL = [:distinct, :group, :having]
VALUE_METHODS = MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS + CLAUSE_METHODS
include Enumerable
include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches, Explain, Delegation
attr_reader :table, :klass, :loaded, :predicate_builder
alias :model :klass
alias :loaded? :loaded
alias :locked? :lock_value
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
end
def initialize_copy(other)
@values = @values.dup
reset
end
def arel_attribute(name) # :nodoc:
klass.arel_attribute(name, table)
end
# Initializes new record from relation while maintaining the current
# scope.
#
# Expects arguments in the same format as {ActiveRecord::Base.new}[rdoc-ref:Core.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
def new(attributes = nil, &block)
scoping { klass.new(scope_for_create(attributes), &block) }
end
alias build new
# 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}[rdoc-ref:Persistence::ClassMethods#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, ...>
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!}[rdoc-ref:Persistence::ClassMethods#create!]
# on the base class. Raises an exception if a validation error occurs.
#
# Expects arguments in the same format as
# {ActiveRecord::Base.create!}[rdoc-ref:Persistence::ClassMethods#create!].
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
def first_or_create(attributes = nil, &block) # :nodoc:
first || create(attributes, &block)
end
def first_or_create!(attributes = nil, &block) # :nodoc:
first || create!(attributes, &block)
end
def first_or_initialize(attributes = nil, &block) # :nodoc:
first || new(attributes, &block)
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
#
def find_or_create_by(attributes, &block)
find_by(attributes) || create(attributes, &block)
end
# Like #find_or_create_by, but calls
# {create!}[rdoc-ref:Persistence::ClassMethods#create!] so an exception
# is raised if the created record is invalid.
def find_or_create_by!(attributes, &block)
find_by(attributes) || create!(attributes, &block)
end
# Like #find_or_create_by, but calls {new}[rdoc-ref:Core#new]
# instead of {create}[rdoc-ref:Persistence::ClassMethods#create].
def find_or_initialize_by(attributes, &block)
find_by(attributes) || new(attributes, &block)
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}[http://guides.rubyonrails.org/active_record_querying.html#running-explain].
def explain
exec_explain(collecting_queries_for_explain { exec_queries })
end
# Converts relation objects to Array.
def to_ary
records.dup
end
alias to_a to_ary
def records # :nodoc:
load
@records
end
# Serializes the relation objects Array.
def encode_with(coder)
coder.represent_seq(nil, records)
end
# Returns size of the records.
def size
loaded? ? @records.length : count(:all)
end
# Returns true if there are no records.
def empty?
return @records.empty? if loaded?
!exists?
end
# Returns true if there are no records.
def none?
return super if block_given?
empty?
end
# Returns true if there are any records.
def any?
return super if block_given?
!empty?
end
# Returns true if there is exactly one record.
def one?
return super if block_given?
limit_value ? records.one? : size == 1
end
# Returns true if there is more than one record.
def many?
return super if block_given?
limit_value ? records.many? : size > 1
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.
def cache_key(timestamp_column = :updated_at)
@cache_keys ||= {}
@cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column)
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.
def scoping
previous, klass.current_scope = klass.current_scope(true), self
yield
ensure
klass.current_scope = previous
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')
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
# Destroys the records by instantiating each
# record and calling its {#destroy}[rdoc-ref:Persistence#destroy] method.
# Each object's callbacks are executed (including <tt>:dependent</tt> 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
def destroy_all
records.each(&:destroy).tap { reset }
end
# Deletes the records without instantiating the records
# first, and hence not calling the {#destroy}[rdoc-ref:Persistence#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
# <tt>:dependent</tt> 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 <tt>before_*</tt> 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
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
# 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>
def load(&block)
exec_queries(&block) unless loaded?
self
end
# Forces reloading of relation.
def reload
reset
load
end
def reset
@to_sql = @arel = @loaded = @should_eager_load = nil
@records = [].freeze
@offsets = {}
self
end
# Returns sql statement for the relation.
#
# User.where(name: 'Oscar').to_sql
# # => SELECT "users".* FROM "users" WHERE "users"."name" = 'Oscar'
def to_sql
@to_sql ||= begin
relation = self
if eager_loading?
apply_join_dependency { |rel, _| relation = rel }
end
conn = klass.connection
conn.unprepared_statement {
conn.to_sql(relation.arel)
}
end
end
# Returns a hash of where conditions.
#
# User.where(name: 'Oscar').where_values_hash
# # => {name: "Oscar"}
def where_values_hash(relation_table_name = klass.table_name)
where_clause.to_h(relation_table_name)
end
def scope_for_create(attributes = nil)
scope = where_values_hash.merge!(create_with_value.stringify_keys)
scope.merge!(attributes) if attributes
scope
end
# Returns true if relation needs eager loading.
def eager_loading?
@should_eager_load ||=
eager_load_values.any? ||
includes_values.any? && (joined_includes_values.any? || references_eager_loaded_tables?)
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] }
def joined_includes_values
includes_values & joins_values
end
# Compares two relations for equality.
def ==(other)
case other
when Associations::CollectionProxy, AssociationRelation
self == other.records
when Relation
other.to_sql == to_sql
when Array
records == other
end
end
def pretty_print(q)
q.pp(records)
end
# Returns true if relation is blank.
def blank?
records.blank?
end
def values
@values.dup
end
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
def empty_scope? # :nodoc:
@values == klass.unscoped.values
end
def has_limit_or_offset? # :nodoc:
limit_value || offset_value
end
def alias_tracker(joins = [], aliases = nil) # :nodoc:
joins += [aliases] if aliases
ActiveRecord::Associations::AliasTracker.create(connection, table.name, joins)
end
protected
def load_records(records)
@records = records.freeze
@loaded = true
end
private
def has_join_values?
joins_values.any? || left_outer_joins_values.any?
end
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
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
def skip_query_cache_if_necessary
if skip_query_cache_value
uncached do
yield
end
else
yield
end
end
def build_preloader
ActiveRecord::Associations::Preloader.new
end
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
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
end
end
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