仅当该字段存在于该文档中时才需要过滤该字段上的mongo文档

Question

我有一个文档集合，每个文档都有自己的一组列。在所有文档中都会出现几栏，而不会出现。需要建立一个查询，仅在该列存在时才在该列中搜索文本

示例：在收藏集文章中：         db.articles.find({}, {Title:1,Conclusions:1})

    { "_id" : ObjectId("5c392c930e7c0058e781a2c4"), "Title" : "Title for article1", "Conclusions" : { "Conclusions" : "Some conclusion" } }
    { "_id" : ObjectId("5c392c930e7c0058e781a2c9"), "Title" : "Title for article2" }
    { "_id" : ObjectId("5c392c930e7c0058e781a2ce"), "Title" : "Title for article3" }
    { "_id" : ObjectId("5c392c940e7c0058e781a2d8"), "Title" : "Title for article4", "Conclusions" : { "Conclusions" : "Some other conclusion" } }

我能够检查列是否存在以下内容：

    db.articles.find({ "Conclusions": { $exists: true, $ne:null } }, {Title:1,Conclusions:1})

但无法使用它来添加第二个条件（下面什么都不返回）

    db.articles.find({ "Conclusions": { $exists: true, $ne:null }, Conclusions: '/other/i' }, {Title:1,Conclusions:1})

预期结果：

    { "_id" : ObjectId("5c392c940e7c0058e781a2d8"), "Title" : "Title for article4", "Conclusions" : { "Conclusions" : "Some other conclusion" } }