猫鼬：查找数组的唯一类别

Question

以下是“文档”的示例，表示 mongodb 中的商店产品。我想知道从节点 api 将类别作为数组检索的最有效方法是什么？例如，我想要 [“女装”、“男装”] 的结果。我真的不想遍历数据库中的所有记录，或者有什么方法可以直接查询类别属性。

 [{
            "name":"eu sit voluptate",
            "description":"Deserunt magna minim in nisi ad nisi amet. Cillum in aliquip ex fugiat ut nisi Lorem amet laboris magna occaecat tempor. Nostrud quis nisi minim aute consectetur quis consectetur in nulla. Laboris velit sunt et adipisicing duis consequat do.\r\n",
            "color":"neutral",
            "price":751.12,
            "category":"womens clothing",
            "subcategory":"tops",
            "id":1,
            "sizes":"XL",
            "images":[
               "https://placeholdit.imgix.net/~text?txtsize=15&txt=320%C3%97320&w=320&h=320"
            ],
            "brand":"paul_smith",
            "created":"2015-01-01T12:53:31 -00:00",
            "inStock":true,
            "sale":[
               {
                  "onSale":false,
                  "salePercOff":10
               }
            ]
         },{
            "name":"sit proident mollit",
            "description":"Occaecat proident adipisicing cillum Lorem in. Nulla ipsum culpa eu proident pariatur culpa. Eiusmod consequat qui ex deserunt sunt ut ullamco labore minim proident sint ipsum officia.\r\n",
            "color":"neutral",
            "price":626.6,
            "category":"mens clothing",
            "subcategory":"jumpers",
            "id":15,
            "sizes":40,
            "images":[
               "https://placeholdit.imgix.net/~text?txtsize=15&txt=320%C3%97320&w=320&h=320"
            ],
            "brand":"james_reed",
            "created":"2014-12-18T03:50:19 -00:00",
            "inStock":true,
            "sale":[
               {
                  "onSale":true,
                  "salePercOff":10
               }
            ]
         }]

Answer 1

答案是一个简单的查询：

db.shop.distinct('category');