module ActiveRecord module Batches # :nodoc: def self.included(base) base.extend(ClassMethods) end # When processing large numbers of records, it's often a good idea to do # so in batches to prevent memory ballooning. module ClassMethods # 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 :batch_size option). # # Example: # # Person.find_each(:conditions => "age > 21") 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 } end self end # Yields each batch of records that was found by the find +options+ as # an array. The size of each batch is set by the :batch_size # option; the default is 1000. # # You can control the starting point for the batch processing by # supplying the :start 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 :start # 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.find_in_batches(:conditions => "age > 21") 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 = {}) raise "You can't specify an order, it's forced to be #{batch_order}" if options[:order] raise "You can't specify a limit, it's forced to be the batch_size" if options[:limit] start = options.delete(:start).to_i batch_size = options.delete(:batch_size) || 1000 with_scope(:find => options.merge(:order => batch_order, :limit => batch_size)) do records = find(:all, :conditions => [ "#{table_name}.#{primary_key} >= ?", start ]) while records.any? yield records break if records.size < batch_size records = find(:all, :conditions => [ "#{table_name}.#{primary_key} > ?", records.last.id ]) end end end private def batch_order "#{table_name}.#{primary_key} ASC" end end end end