ruby - 如何创建 Mongoid "within date range or nil"查询？

Question

我正在尝试为匹配特定日期范围或具有 nil 值的记录创建 Mongoid 查询。这是我的 ruby​​ 代码，它执行我想变成 Mongoid 查询的功能:

class MyModel
  include Mongoid::Document
  field :name
  field :enabled, type: Boolean, default: false
  field :start_date, type: DateTime
  field :end_date, type: DateTime

  def self.active
    documents = where(enabled: true)
    documents = documents.keep_if {|doc| doc.start_date.nil? || doc.start_date <= Date.today}
    documents = documents.keep_if {|doc| doc.end_date.nil? || doc.end_date >= Date.tomorrow}
    documents
  end
end

如何通过将此方法转换为 Mongoid 查询来提高性能？

更新:

这是我用来验证正确行为的 RSpec 测试:

describe '.active' do
  let!(:disabled){ Fabricate(:model, enabled: false, name: 'disabled') }
  let!(:enabled_without_date){ Fabricate(:active_model, name: 'enabled_without_date') }
  let!(:past){ Fabricate(:active_model, start_date: 1.week.ago, end_date: Date.yesterday, name: 'past') }
  let!(:current){ Fabricate(:active_model, start_date: Date.today, end_date: Date.tomorrow, name: 'current') }
  let!(:future){ Fabricate(:active_model, start_date: Date.tomorrow, end_date: 1.week.from_now, name: 'future') }
  
  it 'returns only enabled and within the current time' do
    MyModel.count.should == 5
    models = MyModel.active.to_a
    models.should_not be_empty
    models.should_not include disabled
    models.should_not include past
    models.should_not include future
    models.should include enabled_without_date
    models.should include current
  end
end

Answer 1

如果转换条件:

(start <= X OR start.nil?) AND (end >= Y OR end.nil?)

进入析取形式，你得到:

(start <= X AND end >= Y) OR (start <= X and end.nil?) OR (start.nil? and end >= Y) or (start.nil? and end.nil?)

然后您可以通过单个 $or 子句表达这一点:

$or: [
  {:start_date.lte => start_date, :end_date.gte => end_date},
  {:start_date => nil, :end_date.gte => end_date},
  {:start_date.lte => start_date, :end_date => nil},
  {:start_date => nil, :end_date => nil},
]

如果两个值都必须是 set 或 nil(也就是说，你不能有一个 set 和一个 nil)，这就变得更简单了:

$or: [
  {:start_date.lte => start_date, :end_date.gte => end_date},
  {:start_date => nil},
]

为了满足您的规范，完整的查询将是:

Model.where({
  :enabled => true,
  :$or => [
    {:start_date.lte => Date.today.to_time, :end_date.gte => Date.tomorrow.to_time},
    {:start_date => nil},
  ]
})