猫鼬切片不限制数组大小

Question

我正在开发一个应用程序，但我遇到了 Mongoose 在更新时限制数组大小的问题。我不太熟悉 MongoDB 或 Mongoose，但我希望这个项目能增长我的知识。我尝试了一些在 SOF 上查询的其他解决方案，但 none 似乎对我有用。这是我对问题的细分...

库：猫鼬 5.7.7

总结：在日志文档中，我希望只保留最新的10条日志，旧的被推离阵列。

问题：对于我当前的查询，切片似乎没有限制文档的数量。该阵列只是继续增长。

ActivityLog.updateOne(
  { guild },
  {
    $push: {
      logs: {
        $each: [{ ...log }]
      },
      $slice: -10
    }
  },
  { upsert: true }
);

Answer 1

这在您的实施中实际上可能是一个更大的问题。以下是实际使用中的基本内容，以证明它确实有效：

const { Schema } = mongoose = require('mongoose');

const uri = 'mongodb://localhost:27017/test';
const options = { useNewUrlParser: true, useUnifiedTopology: true };

mongoose.set("debug", true);
mongoose.set("useFindAndModify", false);
mongoose.set("useCreateIndex", true);

const demoSchema = new Schema({
  _id: Number,
  fifo: [Number]
},{ _id: false });

const Demo = mongoose.model('Demo', demoSchema, 'demo');

const log = data => console.log(JSON.stringify(data, undefined, 2));

(async function() {

  try {

    const conn = await mongoose.connect(uri, options);

    await Promise.all(
      Object.values(conn.models).map(m => m.deleteMany())
    );

    let counter = 0;

    await new Promise((resolve, reject) =>
      setInterval(async () => {
        try {
          let result = await Demo.findByIdAndUpdate(
            1,
            { "$push": { "fifo": { "$each": [counter], "$slice": -3 } } },
            { upsert: true, new: true }
          );

          log(result);
        } catch(e) {
          reject(e)
        }
        counter++;
      }, 2000)
    );


  } catch (e) {
    console.error(e);
  } finally {
    mongoose.disconnect();
  }

})()

在几次迭代中（为了简洁起见，这里使用 -3）你会看到：

Mongoose: demo.deleteMany({}, {})
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 0 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    0
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 1 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    0,
    1
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 2 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    0,
    1,
    2
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 3 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    1,
    2,
    3
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 4 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    2,
    3,
    4
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 5 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    3,
    4,
    5
  ],
  "_id": 1,
  "__v": 0
}
Mongoose: demo.findOneAndUpdate({ _id: 1 }, { '$setOnInsert': { __v: 0 }, '$push': { fifo: { '$each': [ 6 ], '$slice': -3 } }}, { upsert: true, remove: false, projection: {}, returnOriginal: false })
{
  "fifo": [
    4,
    5,
    6
  ],
  "_id": 1,
  "__v": 0
}

所以这确实保留了指定 $slice 长度的数组，并且由于负数而从数组的末尾开始，既将数组增长到设定的大小，然后删除除了最后添加的所有内容成员。

猫鼬切片不限制数组大小

Mongoose Slice Not Limiting Array Size

mongoose

mongodb

node.js

mongoose-schema