自动增加Mongo/Mongoose中的文件编号 [英] Auto increment document number in Mongo / Mongoose

问题描述

我的应用程序有多个用户，每个用户都有文档.每个文档都需要有一个序列号，可能看起来像这样:2013-1、2013-2(年份和序列号)，或者可能只是一个简单的数字:1、2、3 ...

My app has several users, each user has documents. Each documents needs to have a sequence number, that may look something like this: 2013-1, 2013-2 (year and sequence number), or perhaps just a simple number: 1, 2, 3...

目前，我正在创建Mongoose文档时从用户设置中分配序列号.根据该序列号和用户设置的数字格式，我将生成最终的文档编号.

Currently, I am assigning the sequence number from user's settings when the Mongoose docuemnt is created. Based on that sequence number and the number format from user's settings, I am generating the final document number.

我意识到，当同时创建2个文档时，它们将获得完全相同的编号，因为在保存文档后，我将在设置中增加序列号.但是我在创建(尚未保存)文档时分配了序列号，因此两个文档的序列号将完全相同.

What I realized is that when 2 documents are created at the same time, they will get exactly the same number, because I am incrementing the sequence number in settings just after I have saved a document. But I am assigning the sequence number when I am creating (not saving yet) the document so the sequence number will be exactly the same for both documents.

我显然需要一种在保存时处理此序号自动递增的方法...

I obviously need a way to handle this sequence number auto-incrementing at the moment of saving...

我如何确保该数字是唯一的并且会自动递增/生成?

How can I assure that this number is unique and automatically incremented/generated?

推荐答案

@emre和@WiredPraire向我指出了正确的方向，但我想为我的问题提供与Mongoose兼容的完整答案.我得到了以下解决方案:

@emre and @WiredPraire pointed me to the right direction, but I wanted to provide a full Mongoose-compatible answer to my question. I ended up with the following solution:

var Settings = new Schema({
  nextSeqNumber: { type: Number, default: 1 }
});

var Document = new Schema({
  _userId: { type: Schema.Types.ObjectId, ref: "User" },
  number: { type: String }
});

// Create a compound unique index over _userId and document number
Document.index({ "_userId": 1, "number": 1 }, { unique: true });

// I make sure this is the last pre-save middleware (just in case)
Document.pre('save', function(next) {
  var doc = this;
  // You have to know the settings_id, for me, I store it in memory: app.current.settings.id
  Settings.findByIdAndUpdate( settings_id, { $inc: { nextSeqNumber: 1 } }, function (err, settings) {
    if (err) next(err);
    doc.number = settings.nextSeqNumber - 1; // substract 1 because I need the 'current' sequence number, not the next
    next();
  });
});

请注意，使用此方法无法在架构中要求数字路径，也没有要点，因为它是自动添加的.

Please note that with this method there is no way to require the number path in the schema, and there is no point as well, because it is automatically added.

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