mongodb - 在集合中查询最新的唯一对象

Question

问题:假设我在一个集合中有以下对象:

如何为每个 "product_id" 返回一条记录，并且只返回具有最高 "version" 编号的记录？这可以在 mongoose 中完成吗？

{
    "_id" : ObjectId("54f765564b10883c1800002a"),
    "total_invoice_fob_case" : 86.70999999999999,
    "status" : "Draft",
    "discount" : "3.40",
    "effective_date" : ISODate("2013-08-01T06:00:00.000Z"),
    "version" : 2,
    "controlstate" : "AB",
    "controlstate_id" : ObjectId("54d510e9e3d793f581b6bb27"),
    "product" : "Product A",
    "product_id" : ObjectId("54f75b5e4b1088801a000627"),
    "size" : "1.75LTR",
    "size_id" : ObjectId("5418a3dd750b4294c2cb3a47"),
    "vendor" : "BEAM SUNTORY",
    "vendor_id" : ObjectId("54ef5aa74b1088781b000169"),
    "product_state_code" : "123",
    "net_fob_cost" : 86.70999999999999,
    "change_reason" : [ 
        "Other"
    ],
    "submitted" : {
        "submitted_date" : ISODate("2014-05-16T06:00:00.000Z")
    }
},
{
    "_id" : ObjectId("54f765564b10883c1800002b"),
    "total_invoice_fob_case" : 86.70999999999999,
    "status" : "Draft",
    "discount" : "4.40",
    "effective_date" : ISODate("2013-08-01T06:00:00.000Z"),
    "version" : 3,
    "controlstate" : "AB",
    "controlstate_id" : ObjectId("54d510e9e3d793f581b6bb27"),
    "product" : "Product A",
    "product_id" : ObjectId("54f75b5e4b1088801a000627"),
    "size" : "1.75LTR",
    "size_id" : ObjectId("5418a3dd750b4294c2cb3a47"),
    "vendor" : "BEAM SUNTORY",
    "vendor_id" : ObjectId("54ef5aa74b1088781b000169"),
    "product_state_code" : "123",
    "net_fob_cost" : 86.70999999999999,
    "change_reason" : [ 
        "Other"
    ],
    "submitted" : {
        "submitted_date" : ISODate("2014-05-16T06:00:00.000Z")
    }
},
{
    "_id" : ObjectId("54f765564b10883c1800002c"),
    "total_invoice_fob_case" : 86.70999999999999,
    "status" : "Draft",
    "discount" : "3.40",
    "effective_date" : ISODate("2013-08-01T06:00:00.000Z"),
    "version" : 2,
    "controlstate" : "AB",
    "controlstate_id" : ObjectId("54d510e9e3d793f581b6bb27"),
    "product" : "Product B",
    "product_id" : ObjectId("54f75b5e4b1088801a000628"),
    "size" : "1.75LTR",
    "size_id" : ObjectId("5418a3dd750b4294c2cb3a47"),
    "vendor" : "BEAM SUNTORY",
    "vendor_id" : ObjectId("54ef5aa74b1088781b000169"),
    "product_state_code" : "123",
    "net_fob_cost" : 86.70999999999999,
    "change_reason" : [ 
        "Other"
    ],
    "submitted" : {
        "submitted_date" : ISODate("2014-05-16T06:00:00.000Z")
    }
}

Answer 1

听起来像是 Mongo 的 aggregation framework 的工作.您可以从 this example 推断如何解决这个问题。

更新:要检索每个具有最高版本的 product_id，您还需要使用 $first :

db.products.aggregate([
  {$sort: {product_id: 1, version: -1}}, // sort first so that $first pulls the correct record
  {$group: {
    _id: {product_id: '$product_id'}, // group by the product_id
    product: {$first: $$ROOT} // only return the first document per group
  }}
]);