查找所有子文档都符合条件的 MongoDB 文档

Question

我有一些Product 文档，每个文档都包含ProductVariation 子文档的列表。我需要找到所有Product 文档，其中ALL 他们的孩子ProductVariation 文档的数量为零。

架构如下所示：

var Product = new mongoose.Schema({
    name: String,
    variations: [ProductVariation]
});

var ProductVariation = new mongoose.Schema({
    type: String,
    quantity: Number,
    price: Number
});

我对 mongodb 有点陌生，所以甚至确定从哪里开始。

Answer 1

尝试使用$not包裹{ "$gt" : 0 }：

> db.products.find()
{ "_id" : ObjectId("5b7cae558ff28edda6ba4a67"), "name" : "widget", "variations" : [ { "type" : "color", "quantity" : 0, "price" : 10 }, { "type" : "size", "quantity" : 0, "price" : 5 } ] }
{ "_id" : ObjectId("5b7cae678ff28edda6ba4a68"), "name" : "foo", "variations" : [ { "type" : "color", "quantity" : 2, "price" : 15 }, { "type" : "size", "quantity" : 0, "price" : 5 } ] }
{ "_id" : ObjectId("5b7cae7f8ff28edda6ba4a69"), "name" : "bar", "variations" : [ { "type" : "color", "quantity" : 0, "price" : 15 }, { "type" : "size", "quantity" : 1, "price" : 5 } ] }

> db.products.find({"variations.quantity": { "$not" : { "$gt" : 0 } } })
{ "_id" : ObjectId("5b7cae558ff28edda6ba4a67"), "name" : "widget", "variations" : [ { "type" : "color", "quantity" : 0, "price" : 10 }, { "type" : "size", "quantity" : 0, "price" : 5 } ] }

它还可以利用{ "variations.quantity" : 1 } 上的索引。