db.collection.insertOne({name: "example"})

db.createCollection("counters")
db.counters.insertOne({_id: "productid", seq: 0})

function getNextSequence(name) {
    var ret = db.counters.findAndModify({
        query: { _id: name },
        update: { $inc: { seq: 1 } },
        new: true
    });
    return ret.seq;
}

db.products.insertOne({
    _id: getNextSequence("productid"),
    name: "example"
})

db.counters.insertOne({_id: "userid", seq: 0})

function getNextSequence(name) {
    var ret = db.counters.findAndModify({
        query: { _id: name },
        update: { $inc: { seq: 1 } },
        new: true
    });
    return ret.seq;
}

db.users.insertOne({
    _id: getNextSequence("userid"),
    name: "John Doe"
})

// MySQL中的產(chǎn)品表
CREATE TABLE products (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(255),
    price DECIMAL(10, 2)
);

// 原有數(shù)據(jù)
INSERT INTO products (name, price) VALUES ('Laptop', 999.99), ('Smartphone', 699.99);

// 在MongoDB中創(chuàng)建計(jì)數(shù)器集合
db.counters.insertOne({_id: "productid", seq: 2}) // 假設(shè)MySQL中已有兩個(gè)產(chǎn)品

// 定義獲取下一個(gè)序列值的函數(shù)
function getNextSequence(name) {
    var ret = db.counters.findAndModify({
        query: { _id: name },
        update: { $inc: { seq: 1 } },
        new: true
    });
    return ret.seq;
}

// 插入新產(chǎn)品時(shí)使用自定義ID
db.products.insertOne({
    _id: getNextSequence("productid"),
    name: "Tablet",
    price: 499.99
});

// 創(chuàng)建計(jì)數(shù)器集合
db.counters.insertOne({_id: "postid", seq: 0})

// 定義獲取下一個(gè)序列值的函數(shù)
function getNextSequence(name) {
    var ret = db.counters.findAndModify({
        query: { _id: name },
        update: { $inc: { seq: 1 } },
        new: true
    });
    return ret.seq;
}

// 插入新文章時(shí)使用自定義ID
db.posts.insertOne({
    _id: getNextSequence("postid"),
    title: "How to Use MongoDB",
    content: "MongoDB is a NoSQL database..."
});

// 生成的短鏈接
var postId = getNextSequence("postid");
var shortLink = `http://blogplatform.com/post/${postId}`; // http://blogplatform.com/post/1

// 創(chuàng)建計(jì)數(shù)器集合
db.counters.insertOne({_id: "orderid", seq: 1000}) // 假設(shè)訂單號(hào)從1001開(kāi)始

// 定義獲取下一個(gè)序列值的函數(shù)
function getNextSequence(name) {
    var ret = db.counters.findAndModify({
        query: { _id: name },
        update: { $inc: { seq: 1 } },
        new: true
    });
    return ret.seq;
}

// 插入新訂單時(shí)使用自定義ID
db.orders.insertOne({
    _id: getNextSequence("orderid"),
    customerName: "Alice",
    items: [
        {productId: 1, quantity: 2},
        {productId: 2, quantity: 1}
    ],
    total: 1699.97
});

// 新生成的訂單號(hào)
var orderId = getNextSequence("orderid");
console.log("New Order ID: " + orderId); // New Order ID: 1001

// 獲取下一個(gè)自增ID的函數(shù)
function getNextSequenceValue(sequenceName) {
    var sequenceDocument = db.counters.findAndModify({
        query: { _id: sequenceName },
        update: { $inc: { sequence_value: 1 } },
        new: true,
        upsert: true
    });
    return sequenceDocument.sequence_value;
}

// 使用示例
var nextUserId = getNextSequenceValue('user_id');
db.users.insert({ _id: nextUserId, name: "John Doe" });

class Snowflake {
    constructor(workerId, datacenterId, sequence = 0) {
        this.workerId = workerId;
        this.datacenterId = datacenterId;
        this.sequence = sequence;
        this.twepoch = 1288834974657n;
        this.workerIdBits = 5n;
        this.datacenterIdBits = 5n;
        this.maxWorkerId = -1n ^ (-1n << this.workerIdBits);
        this.maxDatacenterId = -1n ^ (-1n << this.datacenterIdBits);
        this.sequenceBits = 12n;
        this.workerIdShift = this.sequenceBits;
        this.datacenterIdShift = this.sequenceBits + this.workerIdBits;
        this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.datacenterIdBits;
        this.sequenceMask = -1n ^ (-1n << this.sequenceBits);
        this.lastTimestamp = -1n;
    }

    tilNextMillis(lastTimestamp) {
        let timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }

    timeGen() {
        return BigInt(Date.now());
    }

    nextId() {
        let timestamp = this.timeGen();

        if (timestamp < this.lastTimestamp) {
            throw new Error('Clock moved backwards. Refusing to generate id');
        }

        if (this.lastTimestamp === timestamp) {
            this.sequence = (this.sequence + 1n) & this.sequenceMask;
            if (this.sequence === 0n) {
                timestamp = this.tilNextMillis(this.lastTimestamp);
            }
        } else {
            this.sequence = 0n;
        }

        this.lastTimestamp = timestamp;
        return ((timestamp - this.twepoch) << this.timestampLeftShift) |
            (this.datacenterId << this.datacenterIdShift) |
            (this.workerId << this.workerIdShift) |
            this.sequence;
    }
}

// 使用示例
const snowflake = new Snowflake(1n, 1n);
const id = snowflake.nextId();
console.log(id.toString());  // 生成唯一ID

// 服務(wù)節(jié)點(diǎn)1
const snowflake1 = new Snowflake(1n, 1n);
const id1 = snowflake1.nextId();
console.log(id1.toString());  // 唯一ID

// 服務(wù)節(jié)點(diǎn)2
const snowflake2 = new Snowflake(2n, 1n);
const id2 = snowflake2.nextId();
console.log(id2.toString());  // 唯一ID