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module ActiveRecord
module Batches
class BatchEnumerator
include Enumerable
def initialize(of: 1000, start: nil, finish: nil, relation:) #:nodoc:
@of = of
@relation = relation
@start = start
@finish = finish
end
# Looping through a collection of records from the database (using the
# +all+ method, for example) is very inefficient since it will try to
# instantiate all the objects at once.
#
# In that case, batch processing methods allow you to work with the
# records in batches, thereby greatly reducing memory consumption.
#
# Person.in_batches.each_record do |person|
# person.do_awesome_stuff
# end
#
# Person.where("age > 21").in_batches(of: 10).each_record do |person|
# person.party_all_night!
# end
#
# If you do not provide a block to #each_record, it will return an Enumerator
# for chaining with other methods:
#
# Person.in_batches.each_record.with_index do |person, index|
# person.award_trophy(index + 1)
# end
def each_record
return to_enum(:each_record) unless block_given?
@relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: true).each do |relation|
relation.records.each { |record| yield record }
end
end
# Delegates #delete_all, #update_all, #destroy_all methods to each batch.
#
# People.in_batches.delete_all
# People.where('age < 10').in_batches.destroy_all
# People.in_batches.update_all('age = age + 1')
[:delete_all, :update_all, :destroy_all].each do |method|
define_method(method) do |*args, &block|
@relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: false).each do |relation|
relation.send(method, *args, &block)
end
end
end
# Yields an ActiveRecord::Relation object for each batch of records.
#
# Person.in_batches.each do |relation|
# relation.update_all(awesome: true)
# end
def each
enum = @relation.to_enum(:in_batches, of: @of, start: @start, finish: @finish, load: false)
return enum.each { |relation| yield relation } if block_given?
enum
end
end
end
end
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