[英]Mongoose populate virtual with sort and limit
我正在嘗試編寫一個 mongoose 查詢來檢索一組資產以及這些資產的最新交易。 交易與資產位於不同的集合中。
為此,我首先在資產模型中創建了一個虛擬數組,以將資產與交易聯系起來。
schema.virtual('transactions', {
ref: 'transaction',
localField: '_id',
foreignField: '_asset',
justOne: false
})
然后我在 node.js express 控制器中使用 .populate 進行查詢(注意硬編碼的“limit: 1”在某個時候會變成 N):
exports.getList = function (req, res) {
Model
.find({}, { __v: 0 })
.populate({
path: 'transactions',
options: { sort: { 'created_at': -1}, limit: 1},
})
.lean()
.exec(function (err, model) {
if (err)
res.send(err);
res.json(model);
});
}
我的測試系統中有 3 個資產,每個資產都有一堆交易,它返回前兩個資產的舊交易,而第三個資產沒有任何交易。
當我刪除“limit:1”並返回所有交易時,它會正確排序並返回所有三個資產的交易。
我相信我遇到了這個錯誤:
https://github.com/Automattic/mongoose/issues/4321
關於優雅的解決方法的任何想法?
返回所有交易將不是一個可行的長期解決方案。
這確實是一個棘手的問題。 這里的基礎知識是.populate()
而不是“用虛擬填充”,它的設計目的不是像您在這里期望的那樣工作。
本質上.populate()
本質上是向 MongoDB 發出的另一個查詢以檢索相關數據。 為此,它基本上使用$in
發出一個查詢,其中包含要匹配的目標的所有“相關字段”值。
“問題 4321”的核心是,使用諸如"sort"
和"limit"
之類的選項,需要提供這樣一個$in
參數的實際查詢實際上是一個.aggregate()
語句,它將是能夠“獲得為每個鍵分組的最后n
結果” 。 這實際上並不是 mongoose 目前向 MongoDB 發出的問題,此時按可用操作對n
項進行分組也不太實際。
您可以手動使用.aggregate()
解決這個問題,如所提供列表的末尾所示,但當然僅在少數情況下實際上是可行的。
// Get latest transactions for each master
Transaction.aggregate([
{ '$match': {
'_asset': {
'$in': masters.map(m => m._id)
}
}},
{ '$sort': { '_asset': 1, 'createdAt': -1 } },
{ '$group': {
'_id': '$_asset',
'amount': { '$first': '$amount' },
'createdAt': { '$first': '$createdAt' },
'updatedAt': { '$first': '$updatedAt' },
'did': { '$first': '$_id' }
}},
{ '$project': {
'_id': '$did',
'_asset': '$_id',
'amount': 1,
'createdAt': 1,
'updatedAt': 1
}}
])
它不是很好,也不是真正高效的解決方案,但比其他類似的替代方案要好。 我相信還有更好的方法。
對於您這里的情況,我懷疑有許多類似的情況,您不希望在父文檔中包含“完整”交易列表,即使由於生成的數組的潛在大小而作為參考。 這種“反模式”通常是“虛擬填充”和實際上$lookup
旨在避免的。
但是,在您“獲取最新交易”的特定用例中,這些都不是可行的解決方案。 由於兩者本質上都需要查看“所有”事務,然后只從它們中檢索n
結果。
因此,此處的“最新”或實際上是“最近”的案例實際上退回到“有限數量”的“嵌入”(至少是引用),以提供可行的解決方案。 所以建議就是這樣做,並在父級本身中保留一個"recent"
的交易列表。 這為您提供了包含的場景中的文檔,如下所示:
{
"_id" : ObjectId("5959e34adf833e1451a32661"),
"__v" : 0,
"name" : "One",
"recent" : [
ObjectId("5959e34bdf833e1451a32676"),
ObjectId("5959e34bdf833e1451a32674"),
ObjectId("5959e34bdf833e1451a32672"),
ObjectId("5959e34bdf833e1451a32670"),
ObjectId("5959e34bdf833e1451a3266e")
]
}
請注意,這些不是“所有”相關交易,而只是“最近”交易。 關鍵是只保留一個適合目的的“小”列表。
通過這種方式,您可以直接查詢“父項”,然后將包含"recent"
項的數組進行$slice
。 在清單中,我這樣做:
Master.find().select({ 'recent': { '$slice': 1 } })
這將返回數組中的“最新”條目,而無需向服務器進行任何其他查詢。 在這種情況下,它是“最新的”,因為我們在寫入"transactions"
集合的同時將項目“預先添加”到該數組,該集合包含所有內容:
Transaction.create({ _asset: master._id, amount: data.amount })
.then(transaction =>
Master.update(
{ _id: transaction._asset },
{ "$push": {
"recent": {
"$each": [transaction._id],
"$position": 0,
"$slice": 5
}
}}
)
關鍵元素是$push
到父級中的數組,它在數組的開頭用$position
修改為“preprend”,因此“第一個”項目始終是要添加的“最新”事務,與父母。
然后在這里使用$slice
修飾符將"recent"
數組保持在僅限n
項目的限制。 因此,當添加新項目時,“最舊”項目將被“從列表中刪除”。
這里還有另一個實際目的,即在分頁場景中列出“主”和“交易”時,第一個請求可以直接使用"recent"
數組。 然后對新“頁面”的額外請求,可以簡單地通過$nin
過濾掉"recent"
數組中包含的項目,並使用常規的.skip()
和.limit()
或替代“范圍”分頁實踐來檢索每個“頁面” ”的結果。
要完整演示所有概念,請參閱下面的列表和所有生成的結果。
示范清單:
const async = require('async'),
mongoose = require('mongoose'),
Schema = mongoose.Schema;
mongoose.set('debug',true);
mongoose.Promise = global.Promise;
mongoose.connect('mongodb://localhost/prepend');
const transactionSchema = new Schema({
_asset: { type: Schema.Types.ObjectId, ref: 'Master' },
amount: Number
},{
timestamps: {
createdAt: 'createdAt'
}
});
const Transaction = mongoose.model('Transaction', transactionSchema);
const masterSchema = new Schema({
name: String,
recent: [{ type: Schema.Types.ObjectId, ref: 'Transaction' }]
});
masterSchema.virtual('transactions', {
ref: 'Transaction',
localField: '_id',
foreignField: '_asset',
justOne: false
});
const Master = mongoose.model('Master', masterSchema);
function log(data) {
console.log(JSON.stringify(data, undefined, 2))
}
async.series(
[
// Clean data
(callback) =>
async.each(mongoose.models,(model,callback) =>
model.remove({},callback),callback),
// Create Masters
(callback) =>
Master.insertMany(['One','Two'].map( name => ({ name })),callback),
// Add 10 transactions to each master
(callback) =>
async.each(['One','Two'],(name,callback) =>
async.eachSeries(
Array.apply(null,Array(10)).map((e,i) => ({ name, amount: i+1 })),
(data,callback) => {
Master.findOne({ name: data.name })
.then(master =>
Transaction.create({ _asset: master._id, amount: data.amount })
)
.then(transaction =>
Master.update(
{ _id: transaction._asset },
{ "$push": {
"recent": {
"$each": [transaction._id],
"$position": 0,
"$slice": 5
}
}}
)
)
.then(res => callback())
.catch(callback)
},
callback
),
callback),
// Show populated recent 1 entry only
(callback) =>
Master.find().select({ 'recent': { '$slice': 1 } })
.populate('recent').exec((err,results) => {
if (err) callback(err);
log(results);
callback();
}),
// Populate recent - page 1 then fetch next page
(callback) =>
async.waterfall(
[
(callback) =>
Master.findOne({ name: 'One' }).populate('recent')
.lean()
.exec((err,master) => {
if (err) callback(err);
log(master);
callback(null,{
_asset: master._id,
exclude: master.recent.map( r => r._id )
});
}),
(options,callback) =>
Transaction.find({
_asset: options._asset,
_id: { '$nin': options.exclude }
}).sort({ 'createdAt': -1 }).limit(5)
.exec((err,transactions) => {
if (err) callback(err);
log(transactions)
callback();
})
],
callback
),
// Issue 4321 - Fix - Manual populate with aggregate
(callback) =>
Master.find().select('-recent').exec()
.then(masters => {
// Get latest transactions for each master
Transaction.aggregate([
{ '$match': {
'_asset': {
'$in': masters.map(m => m._id)
}
}},
{ '$sort': { '_asset': 1, 'createdAt': -1 } },
{ '$group': {
'_id': '$_asset',
'amount': { '$first': '$amount' },
'createdAt': { '$first': '$createdAt' },
'updatedAt': { '$first': '$updatedAt' },
'did': { '$first': '$_id' }
}},
{ '$project': {
'_id': '$did',
'_asset': '$_id',
'amount': 1,
'createdAt': 1,
'updatedAt': 1
}}
]).exec((err,transactions) => {
// Map latest transactions to master
masters = masters.map(
m => Object.assign(
m.toObject(),
{
transactions: transactions.filter(
t => t._asset.toHexString() === m._id.toHexString()
)
}
)
);
log(masters);
callback();
})
}).catch(callback)
],
(err) => {
if (err) throw err;
mongoose.disconnect();
}
);
演示輸出
Mongoose: transactions.remove({}, {})
Mongoose: masters.remove({}, {})
Mongoose: masters.insertMany([ { __v: 0, name: 'One', _id: 5959e34adf833e1451a32661, recent: [] }, { __v: 0, name: 'Two', _id: 5959e34adf833e1451a32662, recent: [] } ], null)
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:14 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:14 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 1, _id: ObjectId("5959e34adf833e1451a32663"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 1, _id: ObjectId("5959e34adf833e1451a32664"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34adf833e1451a32664") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34adf833e1451a32663") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 2, _id: ObjectId("5959e34bdf833e1451a32665"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 2, _id: ObjectId("5959e34bdf833e1451a32666"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32666") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32665") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 3, _id: ObjectId("5959e34bdf833e1451a32667"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 3, _id: ObjectId("5959e34bdf833e1451a32668"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32668") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32667") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 4, _id: ObjectId("5959e34bdf833e1451a32669"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 4, _id: ObjectId("5959e34bdf833e1451a3266a"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266a") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32669") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 5, _id: ObjectId("5959e34bdf833e1451a3266b"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 5, _id: ObjectId("5959e34bdf833e1451a3266c"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266c") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266b") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 6, _id: ObjectId("5959e34bdf833e1451a3266d"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 6, _id: ObjectId("5959e34bdf833e1451a3266e"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266e") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266d") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 7, _id: ObjectId("5959e34bdf833e1451a3266f"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 7, _id: ObjectId("5959e34bdf833e1451a32670"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32670") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a3266f") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 8, _id: ObjectId("5959e34bdf833e1451a32671"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 8, _id: ObjectId("5959e34bdf833e1451a32672"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32672") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32671") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 9, _id: ObjectId("5959e34bdf833e1451a32673"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 9, _id: ObjectId("5959e34bdf833e1451a32674"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32674") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32673") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: masters.findOne({ name: 'Two' }, { fields: {} })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32662"), amount: 10, _id: ObjectId("5959e34bdf833e1451a32675"), __v: 0 })
Mongoose: transactions.insert({ updatedAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), createdAt: new Date("Mon, 03 Jul 2017 06:25:15 GMT"), _asset: ObjectId("5959e34adf833e1451a32661"), amount: 10, _id: ObjectId("5959e34bdf833e1451a32676"), __v: 0 })
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32661") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32676") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.update({ _id: ObjectId("5959e34adf833e1451a32662") }, { '$push': { recent: { '$each': [ ObjectId("5959e34bdf833e1451a32675") ], '$slice': 5, '$position': 0 } } }, {})
Mongoose: masters.find({}, { fields: { recent: { '$slice': 1 } } })
Mongoose: transactions.find({ _id: { '$in': [ ObjectId("5959e34bdf833e1451a32676"), ObjectId("5959e34bdf833e1451a32675") ] } }, { fields: {} })
[
{
"_id": "5959e34adf833e1451a32661",
"__v": 0,
"name": "One",
"recent": [
{
"_id": "5959e34bdf833e1451a32676",
"updatedAt": "2017-07-03T06:25:15.282Z",
"createdAt": "2017-07-03T06:25:15.282Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 10,
"__v": 0
}
]
},
{
"_id": "5959e34adf833e1451a32662",
"__v": 0,
"name": "Two",
"recent": [
{
"_id": "5959e34bdf833e1451a32675",
"updatedAt": "2017-07-03T06:25:15.280Z",
"createdAt": "2017-07-03T06:25:15.280Z",
"_asset": "5959e34adf833e1451a32662",
"amount": 10,
"__v": 0
}
]
}
]
Mongoose: masters.findOne({ name: 'One' }, { fields: {} })
Mongoose: transactions.find({ _id: { '$in': [ ObjectId("5959e34bdf833e1451a32676"), ObjectId("5959e34bdf833e1451a32674"), ObjectId("5959e34bdf833e1451a32672"), ObjectId("5959e34bdf833e1451a32670"), ObjectId("5959e34bdf833e1451a3266e") ] } }, { fields: {} })
{
"_id": "5959e34adf833e1451a32661",
"__v": 0,
"name": "One",
"recent": [
{
"_id": "5959e34bdf833e1451a32676",
"updatedAt": "2017-07-03T06:25:15.282Z",
"createdAt": "2017-07-03T06:25:15.282Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 10,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a32674",
"updatedAt": "2017-07-03T06:25:15.264Z",
"createdAt": "2017-07-03T06:25:15.264Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 9,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a32672",
"updatedAt": "2017-07-03T06:25:15.216Z",
"createdAt": "2017-07-03T06:25:15.216Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 8,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a32670",
"updatedAt": "2017-07-03T06:25:15.195Z",
"createdAt": "2017-07-03T06:25:15.195Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 7,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a3266e",
"updatedAt": "2017-07-03T06:25:15.180Z",
"createdAt": "2017-07-03T06:25:15.180Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 6,
"__v": 0
}
]
}
Mongoose: transactions.find({ _id: { '$nin': [ ObjectId("5959e34bdf833e1451a32676"), ObjectId("5959e34bdf833e1451a32674"), ObjectId("5959e34bdf833e1451a32672"), ObjectId("5959e34bdf833e1451a32670"), ObjectId("5959e34bdf833e1451a3266e") ] }, _asset: ObjectId("5959e34adf833e1451a32661") }, { sort: { createdAt: -1 }, limit: 5, fields: {} })
[
{
"_id": "5959e34bdf833e1451a3266c",
"updatedAt": "2017-07-03T06:25:15.164Z",
"createdAt": "2017-07-03T06:25:15.164Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 5,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a3266a",
"updatedAt": "2017-07-03T06:25:15.135Z",
"createdAt": "2017-07-03T06:25:15.135Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 4,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a32668",
"updatedAt": "2017-07-03T06:25:15.080Z",
"createdAt": "2017-07-03T06:25:15.080Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 3,
"__v": 0
},
{
"_id": "5959e34bdf833e1451a32666",
"updatedAt": "2017-07-03T06:25:15.039Z",
"createdAt": "2017-07-03T06:25:15.039Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 2,
"__v": 0
},
{
"_id": "5959e34adf833e1451a32664",
"updatedAt": "2017-07-03T06:25:15.009Z",
"createdAt": "2017-07-03T06:25:15.009Z",
"_asset": "5959e34adf833e1451a32661",
"amount": 1,
"__v": 0
}
]
Mongoose: masters.find({}, { fields: { recent: 0 } })
Mongoose: transactions.aggregate([ { '$match': { _asset: { '$in': [ 5959e34adf833e1451a32661, 5959e34adf833e1451a32662 ] } } }, { '$sort': { _asset: 1, createdAt: -1 } }, { '$group': { _id: '$_asset', amount: { '$first': '$amount' }, createdAt: { '$first': '$createdAt' }, updatedAt: { '$first': '$updatedAt' }, did: { '$first': '$_id' } } }, { '$project': { _id: '$did', _asset: '$_id', amount: 1, createdAt: 1, updatedAt: 1 } } ], {})
[
{
"_id": "5959e34adf833e1451a32661",
"__v": 0,
"name": "One",
"transactions": [
{
"amount": 10,
"createdAt": "2017-07-03T06:25:15.282Z",
"updatedAt": "2017-07-03T06:25:15.282Z",
"_id": "5959e34bdf833e1451a32676",
"_asset": "5959e34adf833e1451a32661"
}
]
},
{
"_id": "5959e34adf833e1451a32662",
"__v": 0,
"name": "Two",
"transactions": [
{
"amount": 10,
"createdAt": "2017-07-03T06:25:15.280Z",
"updatedAt": "2017-07-03T06:25:15.280Z",
"_id": "5959e34bdf833e1451a32675",
"_asset": "5959e34adf833e1451a32662"
}
]
}
]
對於那些在 2021 年閱讀本文的人,從mongoose 5.12.3
可以在模型中完成以下操作:
schema.virtual('transactions', {
ref: 'transaction',
localField: '_id',
foreignField: '_asset',
justOne: false,
options: { sort: { 'createdAt': -1}, limit: 1},
})
然后在控制器中:
exports.getList = function (req, res) {
Model
.find({}, { __v: 0 })
.populate({
path: 'transactions',
})
.lean()
.exec(function (err, model) {
if (err)
res.send(err);
res.json(model);
});
}
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.