这不是理想的解决方案,但这是一种仅复制粘贴大部分find_in_batches
但产生关系而不是记录数组(未经测试)的方法 - 只需将其修补到Relation
:
def in_batches( options = {} )
relation = self
unless arel.orders.blank? && arel.taken.blank?
ActiveRecord::Base.logger.warn("Scoped order and limit are ignored, it's forced to be batch order and batch size")
end
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)
end
start = options.delete(:start)
batch_size = options.delete(:batch_size) || 1000
relation = relation.reorder(batch_order).limit(batch_size)
relation = start ? relation.where(table[primary_key].gteq(start)) : relation
while ( size = relation.size ) > 0
yield relation
break if size < batch_size
primary_key_offset = relation.last.id
if primary_key_offset
relation = relation.where(table[primary_key].gt(primary_key_offset))
else
raise "Primary key not included in the custom select clause"
end
end
end
有了这个,你应该能够做到:
Cars.where(:engine => "Turbo").in_batches do |relation|
relation.pluck(:id)
end
这可能不是最好的实现(尤其是关于primary_key_offset 计算,它会实例化一条记录),但你得到了精神。