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require 'active_support/core_ext/object/blank'
module ActiveRecord
module Batches # :nodoc:
# Yields each record that was found by the find +options+. The find is
# performed by find_in_batches with a batch size of 1000 (or as
# specified by the <tt>:batch_size</tt> option).
# Example:
# Person.where("age > 21").find_each do |person|
# person.party_all_night!
# end
# Note: This method is only intended to use for batch processing of
# large amounts of records that wouldn't fit in memory all at once. If
# you just need to loop over less than 1000 records, it's probably
# better just to use the regular find methods.
def find_each(options = {})
find_in_batches(options) do |records|
records.each { |record| yield record }
# Yields each batch of records that was found by the find +options+ as
# an array. The size of each batch is set by the <tt>:batch_size</tt>
# option; the default is 1000.
# You can control the starting point for the batch processing by
# supplying the <tt>:start</tt> option. This is especially useful if you
# want multiple workers dealing with the same processing queue. You can
# make worker 1 handle all the records between id 0 and 10,000 and
# worker 2 handle from 10,000 and beyond (by setting the <tt>:start</tt>
# option on that worker).
# It's not possible to set the order. That is automatically set to
# ascending on the primary key ("id ASC") to make the batch ordering
# work. This also mean that this method only works with integer-based
# primary keys. You can't set the limit either, that's used to control
# the the batch sizes.
# Example:
# Person.where("age > 21").find_in_batches do |group|
# sleep(50) # Make sure it doesn't get too crowded in there!
# group.each { |person| person.party_all_night! }
# end
def find_in_batches(options = {})
relation = self
if orders.present? || taken.present?
ActiveRecord::Base.logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
if (finder_options = options.except(:start, :batch_size)).present?
raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order].present?
raise "You can't specify a limit, it's forced to be the batch_size" if options[:limit].present?
relation = apply_finder_options(finder_options)
start = options.delete(:start).to_i
batch_size = options.delete(:batch_size) || 1000
relation = relation.except(:order).order(batch_order).limit(batch_size)
records = relation.where(primary_key.gteq(start)).all
while records.any?
yield records
break if records.size < batch_size
if primary_key_offset =
records = relation.where(
raise "Primary key not included in the custom select clause"
def batch_order
"#{@klass.table_name}.#{@klass.primary_key} ASC"
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