activerecord-import/lib/activerecord-import/synchronize.rb

55 lines
2.1 KiB
Ruby

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.find_by_author("Zach")
# <.. 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.find_by_author("Zach")
# <.. 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=[self.primary_key])
return if instances.empty?
conditions = {}
order = ""
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.find( :all, :conditions=>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
if matched_instance
instance.clear_aggregation_cache
instance.clear_association_cache
instance.instance_variable_set '@attributes', matched_instance.attributes
end
end
end
# See ActiveRecord::ConnectionAdapters::AbstractAdapter.synchronize
def synchronize(instances, key=[ActiveRecord::Base.primary_key])
self.class.synchronize(instances, key)
end
end
end