activerecord/lib/active_record/relation.rb
# frozen_string_literal: true
module ActiveRecord
# = Active Record \Relation
class Relation
class ExplainProxy # :nodoc:
def initialize(relation, options)
@relation = relation
@options = options
end
def inspect
exec_explain { @relation.send(:exec_queries) }
end
def average(column_name)
exec_explain { @relation.average(column_name) }
end
def count(column_name = nil)
exec_explain { @relation.count(column_name) }
end
def first(limit = nil)
exec_explain { @relation.first(limit) }
end
def last(limit = nil)
exec_explain { @relation.last(limit) }
end
def maximum(column_name)
exec_explain { @relation.maximum(column_name) }
end
def minimum(column_name)
exec_explain { @relation.minimum(column_name) }
end
def pluck(*column_names)
exec_explain { @relation.pluck(*column_names) }
end
def sum(identity_or_column = nil)
exec_explain { @relation.sum(identity_or_column) }
end
private
def exec_explain(&block)
@relation.exec_explain(@relation.collecting_queries_for_explain { block.call }, @options)
end
end
MULTI_VALUE_METHODS = [:includes, :eager_load, :preload, :select, :group,
:order, :joins, :left_outer_joins, :references,
:extending, :unscope, :optimizer_hints, :annotate,
:with]
SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering, :strict_loading,
:reverse_order, :distinct, :create_with, :skip_query_cache]
CLAUSE_METHODS = [:where, :having, :from]
INVALID_METHODS_FOR_DELETE_ALL = [:distinct, :with]
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
attr_accessor :skip_preloading_value
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
@loaded = false
@predicate_builder = predicate_builder
@delegate_to_klass = false
@future_result = nil
@records = nil
@async = false
@none = false
end
def initialize_copy(other)
@values = @values.dup
reset
end
def bind_attribute(name, value) # :nodoc:
if reflection = klass._reflect_on_association(name)
name = reflection.foreign_key
value = value.read_attribute(reflection.association_primary_key) unless value.nil?
end
attr = table[name]
bind = predicate_builder.build_bind_attribute(attr.name, value)
yield attr, bind
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)
if attributes.is_a?(Array)
attributes.collect { |attr| new(attr, &block) }
else
block = current_scope_restoring_block(&block)
scoping { _new(attributes, &block) }
end
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
block = current_scope_restoring_block(&block)
scoping { _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
block = current_scope_restoring_block(&block)
scoping { _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
# # 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
# ActiveRecord::RecordNotFound exception.
#
# Please note <b>this method is not atomic</b>, 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.
def find_or_create_by(attributes, &block)
find_by(attributes) || create_or_find_by(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_or_find_by!(attributes, &block)
end
# 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).
# * Columns with unique database constraints should not have uniqueness validations defined,
# otherwise #create will fail due to validation errors and #find_by will never be called.
#
# 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.
def create_or_find_by(attributes, &block)
transaction(requires_new: true) { create(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
if lease_connection.transaction_open?
where(attributes).lock.find_by!(attributes)
else
find_by!(attributes)
end
end
# Like #create_or_find_by, but calls
# {create!}[rdoc-ref:Persistence::ClassMethods#create!] so an exception
# is raised if the created record is invalid.
def create_or_find_by!(attributes, &block)
transaction(requires_new: true) { create!(attributes, &block) }
rescue ActiveRecord::RecordNotUnique
if lease_connection.transaction_open?
where(attributes).lock.find_by!(attributes)
else
find_by!(attributes)
end
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.
#
# User.all.explain
# # EXPLAIN SELECT `users`.* FROM `users`
# # ...
#
# 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.
#
# To run EXPLAIN on queries created by +first+, +pluck+ and +count+, call
# these methods on +explain+:
#
# User.all.explain.count
# # EXPLAIN SELECT COUNT(*) FROM `users`
# # ...
#
# The column name can be passed if required:
#
# User.all.explain.maximum(:id)
# # EXPLAIN SELECT MAX(`users`.`id`) FROM `users`
# # ...
#
# Please see further details in the
# {Active Record Query Interface guide}[https://guides.rubyonrails.org/active_record_querying.html#running-explain].
def explain(*options)
ExplainProxy.new(self, options)
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
if loaded?
records.length
else
count(:all)
end
end
# Returns true if there are no records.
def empty?
return true if @none
if loaded?
records.empty?
else
!exists?
end
end
# 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 (<tt>===</tt>).
#
# posts.none?(Comment) # => true or false
def none?(*args)
return true if @none
return super if args.present? || block_given?
empty?
end
# 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 (<tt>===</tt>).
#
# posts.any?(Post) # => true or false
def any?(*args)
return false if @none
return super if args.present? || block_given?
!empty?
end
# 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 (<tt>===</tt>).
#
# posts.one?(Post) # => true or false
def one?(*args)
return false if @none
return super if args.present? || block_given?
return records.one? if loaded?
limited_count == 1
end
# Returns true if there is more than one record.
def many?
return false if @none
return super if block_given?
return records.many? if loaded?
limited_count > 1
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)
def cache_key(timestamp_column = "updated_at")
@cache_keys ||= {}
@cache_keys[timestamp_column] ||= klass.collection_cache_key(self, timestamp_column)
end
def compute_cache_key(timestamp_column = :updated_at) # :nodoc:
query_signature = ActiveSupport::Digest.hexdigest(to_sql)
key = "#{klass.model_name.cache_key}/query-#{query_signature}"
if collection_cache_versioning
key
else
"#{key}-#{compute_cache_version(timestamp_column)}"
end
end
private :compute_cache_key
# 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%')
def cache_version(timestamp_column = :updated_at)
if collection_cache_versioning
@cache_versions ||= {}
@cache_versions[timestamp_column] ||= compute_cache_version(timestamp_column)
end
end
def compute_cache_version(timestamp_column) # :nodoc:
timestamp_column = timestamp_column.to_s
if loaded?
size = records.size
if size > 0
timestamp = records.map { |record| record.read_attribute(timestamp_column) }.max
end
else
collection = eager_loading? ? apply_join_dependency : self
with_connection do |c|
column = c.visitor.compile(table[timestamp_column])
select_values = "COUNT(*) AS #{adapter_class.quote_column_name("size")}, MAX(%s) AS timestamp"
if collection.has_limit_or_offset?
query = collection.select("#{column} AS collection_cache_key_timestamp")
query._select!(table[Arel.star]) if distinct_value && collection.select_values.empty?
subquery_alias = "subquery_for_cache_key"
subquery_column = "#{subquery_alias}.collection_cache_key_timestamp"
arel = query.build_subquery(subquery_alias, select_values % subquery_column)
else
query = collection.unscope(:order)
query.select_values = [select_values % column]
arel = query.arel
end
size, timestamp = c.select_rows(arel, nil).first
if size
column_type = klass.type_for_attribute(timestamp_column)
timestamp = column_type.deserialize(timestamp)
else
size = 0
end
end
end
if timestamp
"#{size}-#{timestamp.utc.to_fs(cache_timestamp_format)}"
else
"#{size}"
end
end
private :compute_cache_version
# Returns a cache key along with the version.
def cache_key_with_version
if version = cache_version
"#{cache_key}-#{version}"
else
cache_key
end
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
#
# If <tt>all_queries: true</tt> 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.
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
def _exec_scope(...) # :nodoc:
@delegate_to_klass = true
registry = klass.scope_registry
_scoping(nil, registry) { instance_exec(...) || self }
ensure
@delegate_to_klass = false
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. 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'"))
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.with_connection do |c|
c.update(stmt, "#{klass} Update All").tap { reset }
end
end
def update(id = :all, attributes) # :nodoc:
if id == :all
each { |record| record.update(attributes) }
else
klass.update(id, attributes)
end
end
def update!(id = :all, attributes) # :nodoc:
if id == :all
each { |record| record.update!(attributes) }
else
klass.update!(id, attributes)
end
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.
# * <tt>:touch</tt> 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)
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
# 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'"
def touch_all(*names, time: nil)
update_all klass.touch_attributes_with_time(*names, time: time)
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
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.with_connection do |c|
c.delete(stmt, "#{klass} Delete All").tap { reset }
end
end
# Finds and destroys all records matching the specified conditions.
# This is short-hand for <tt>relation.where(condition).destroy_all</tt>.
# 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)
def destroy_by(*args)
where(*args).destroy_all
end
# Finds and deletes all records matching the specified conditions.
# This is short-hand for <tt>relation.where(condition).delete_all</tt>.
# Returns the number of rows affected.
#
# If no record is found, returns <tt>0</tt> 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)
def delete_by(*args)
where(*args).delete_all
end
# 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}[https://guides.rubyonrails.org/configuring.html#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 <tt>ASYNC</tt>:
#
# ASYNC Post Load (0.0ms) (db time 2ms) SELECT "posts".* FROM "posts" LIMIT 100
def load_async
with_connection do |c|
return load if !c.async_enabled?
unless loaded?
result = exec_main_query(async: c.current_transaction.closed?)
if result.is_a?(Array)
@records = result
else
@future_result = result
end
@loaded = true
end
end
self
end
# Returns <tt>true</tt> if the relation was scheduled on the background
# thread pool.
def scheduled?
!!@future_result
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)
if !loaded? || scheduled?
@records = exec_queries(&block)
@loaded = true
end
self
end
# Forces reloading of relation.
def reload
reset
load
end
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
# 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 ||= if eager_loading?
apply_join_dependency do |relation, join_dependency|
relation = join_dependency.apply_column_aliases(relation)
relation.to_sql
end
else
klass.with_connection do |conn|
conn.unprepared_statement { conn.to_sql(arel) }
end
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) # :nodoc:
where_clause.to_h(relation_table_name)
end
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
# 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. <tt>{ a: :b } & { a: [:b, :c] }</tt>
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(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
# Returns true if relation is blank.
def blank?
records.blank?
end
def values
@values.dup
end
def values_for_queries # :nodoc:
@values.except(:extending, :skip_query_cache, :strict_loading)
end
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
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:
ActiveRecord::Associations::AliasTracker.create(lease_connection, table.name, joins, aliases)
end
class StrictLoadingScope # :nodoc:
def self.empty_scope?
true
end
def self.strict_loading_value
true
end
end
def preload_associations(records) # :nodoc:
preload = preload_values
preload += includes_values unless eager_loading?
scope = strict_loading_value ? StrictLoadingScope : nil
preload.each do |associations|
ActiveRecord::Associations::Preloader.new(records: records, associations: associations, scope: scope).call
end
end
protected
def load_records(records)
@records = records.freeze
@loaded = true
end
private
def already_in_scope?(registry)
@delegate_to_klass && registry.current_scope(klass, true)
end
def global_scope?(registry)
registry.global_current_scope(klass, true)
end
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
def _new(attributes, &block)
klass.new(attributes, &block)
end
def _create(attributes, &block)
klass.create(attributes, &block)
end
def _create!(attributes, &block)
klass.create!(attributes, &block)
end
def _scoping(scope, registry, all_queries = false)
previous = registry.current_scope(klass, true)
registry.set_current_scope(klass, scope)
if all_queries
previous_global = registry.global_current_scope(klass, true)
registry.set_global_current_scope(klass, scope)
end
yield
ensure
registry.set_current_scope(klass, previous)
if all_queries
registry.set_global_current_scope(klass, previous_global)
end
end
def _substitute_values(values)
values.map do |name, value|
attr = table[name]
if Arel.arel_node?(value)
if value.is_a?(Arel::Nodes::SqlLiteral)
value = Arel::Nodes::Grouping.new(value)
end
else
type = klass.type_for_attribute(attr.name)
value = predicate_builder.build_bind_attribute(attr.name, type.cast(value))
end
[attr, value]
end
end
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
def exec_queries(&block)
skip_query_cache_if_necessary do
rows = if scheduled?
future = @future_result
@future_result = nil
future.result
else
exec_main_query
end
records = instantiate_records(rows, &block)
preload_associations(records) unless skip_preloading_value
records.each(&:readonly!) if readonly_value
records.each { |record| record.strict_loading!(strict_loading_value) } unless strict_loading_value.nil?
records
end
end
def exec_main_query(async: false)
if @none
if async
return FutureResult.wrap([])
else
return []
end
end
skip_query_cache_if_necessary do
if where_clause.contradiction?
[].freeze
elsif eager_loading?
with_connection do |c|
apply_join_dependency do |relation, join_dependency|
if relation.null_relation?
[].freeze
else
relation = join_dependency.apply_column_aliases(relation)
@_join_dependency = join_dependency
c.select_all(relation.arel, "SQL", async: async)
end
end
end
else
klass._query_by_sql(arel, async: async)
end
end
end
def instantiate_records(rows, &block)
return [].freeze if rows.empty?
if eager_loading?
records = @_join_dependency.instantiate(rows, strict_loading_value, &block).freeze
@_join_dependency = nil
records
else
klass._load_from_sql(rows, &block).freeze
end
end
def skip_query_cache_if_necessary(&block)
if skip_query_cache_value
uncached(&block)
else
yield
end
end
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
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
def limited_count
limit_value ? count : limit(2).count
end
end
end