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# frozen_string_literal: true
module ActiveRecord # :nodoc:
class Base # :nodoc:
# Synchronizes the passed in ActiveRecord instances with data
# from the database. This is like calling reload on an individual
# ActiveRecord instance but it is intended for use on multiple instances.
#
# This uses one query for all instance updates and then updates existing
# instances rather sending one query for each instance
#
# == Examples
# # Synchronizing existing models by matching on the primary key field
# posts = Post.where(author: "Zach").first
# <.. out of system changes occur to change author name from Zach to Zachary..>
# Post.synchronize posts
# posts.first.author # => "Zachary" instead of Zach
#
# # Synchronizing using custom key fields
# posts = Post.where(author: "Zach").first
# <.. out of system changes occur to change the address of author 'Zach' to 1245 Foo Ln ..>
# Post.synchronize posts, [:name] # queries on the :name column and not the :id column
# posts.first.address # => "1245 Foo Ln" instead of whatever it was
#
def self.synchronize(instances, keys = [primary_key])
return if instances.empty?
conditions = {}
key_values = keys.map { |key| instances.map(&key.to_sym) }
keys.zip(key_values).each { |key, values| conditions[key] = values }
order = keys.map { |key| "#{key} ASC" }.join(",")
klass = instances.first.class
fresh_instances = klass.unscoped.where(conditions).order(order)
instances.each do |instance|
matched_instance = fresh_instances.detect do |fresh_instance|
keys.all? { |key| fresh_instance.send(key) == instance.send(key) }
end
next unless matched_instance
instance.instance_variable_set :@association_cache, {}
instance.send :clear_aggregation_cache if instance.respond_to?(:clear_aggregation_cache, true)
instance.instance_variable_set :@attributes, matched_instance.instance_variable_get(:@attributes)
if instance.respond_to?(:clear_changes_information)
instance.clear_changes_information # Rails 4.2 and higher
else
instance.instance_variable_set :@attributes_cache, {} # Rails 4.0, 4.1
instance.changed_attributes.clear # Rails 3.2
instance.previous_changes.clear
end
# Since the instance now accurately reflects the record in
# the database, ensure that instance.persisted? is true.
instance.instance_variable_set '@new_record', false
instance.instance_variable_set '@destroyed', false
end
end
# See ActiveRecord::ConnectionAdapters::AbstractAdapter.synchronize
def synchronize(instances, key = [ActiveRecord::Base.primary_key])
self.class.synchronize(instances, key)
end
end
end
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