--- /dev/null
+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
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