Method: ActiveRecord::Batches#find_in_batches

Defined in:
activerecord/lib/active_record/relation/batches.rb

#find_in_batches(options = {}) ⇒ Object

Yields each batch of records that was found by the find options as an array.

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

Options

  • :batch_size - Specifies the size of the batch. Default to 1000.

  • :start - Specifies the starting point for the batch processing.

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).

# Let's process the next 2000 records
Person.find_in_batches(start: 2000, batch_size: 2000) do |group|
  group.each { |person| person.party_all_night! }
end

NOTE: 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 means that this method only works with integer-based primary keys.

NOTE: You can’t set the limit either, that’s used to control the batch sizes.



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# File 'activerecord/lib/active_record/relation/batches.rb', line 87

def find_in_batches(options = {})
  options.assert_valid_keys(:start, :batch_size)

  relation = self

  if logger && (arel.orders.present? || arel.taken.present?)
    logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
  end

  start = options.delete(:start)
  batch_size = options.delete(:batch_size) || 1000

  relation = relation.reorder(batch_order).limit(batch_size)
  records = start ? relation.where(table[primary_key].gteq(start)).to_a : relation.to_a

  while records.any?
    records_size = records.size
    primary_key_offset = records.last.id

    yield records

    break if records_size < batch_size

    if primary_key_offset
      records = relation.where(table[primary_key].gt(primary_key_offset)).to_a
    else
      raise "Primary key not included in the custom select clause"
    end
  end
end