ActiveRecord Rails Find Relations in Batches

find_relations_in_batches.rb

  # Finds and yields relations in batches. Adapted from record.find_in_batches since that yields
  # arrays and we want to operate on relationships.
  # Adapted from:
  #   https://github.com/rails/rails/blob/4-2-stable/activerecord/lib/active_record/relation/batches.rb#L98-L115
  def find_in_batches(target, batch_size: default_batch_size, start: nil)
    relation = target
    if logger && (target.arel.orders.present? || target.arel.taken.present?)
      logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
    end
    relation = relation.reorder(target.send(:batch_order)).limit(batch_size)
    records = start ? relation.where(target.table[target.primary_key].gteq(start)) : relation

    while (records_size = records.length) > 0
      primary_key_offset = records.last.id
      fail "Primary key not included in the custom select clause" unless primary_key_offset

      yield records

      break if records_size < batch_size

      records = relation.where(target.table[target.primary_key].gt(primary_key_offset))
    end
  end