在Node.js MySQL中的连接池中切换数据库 [英] Switch database in a connection pool in nodejs MySQL

问题描述

使用连接池在nodejs中连接到MySQL后，如何切换数据库?

How can I switch the database after connecting to MySQL in nodejs using connection pool?

我曾经使用与MySQL的常规连接，因为它有一些问题现在我想使用连接池.但是，在与MySQL建立连接后如何更改数据库?

I used to use the normal connection with MySQL since it has some issue now I would like to use the connection pooling. But how can I change the database after creating a connection with MySQL?

这是我更改数据库的方式:

Here is how I change the database:

conn.changeUser({
    database: req.session.dbname
}, function (err) {
    if (err) {
        console.log(err);
    } else {
        next();
    }
});

但是现在它显示conn.changeUser不是函数

But now it shows conn.changeUser is not a function

这是与mysql连接的方法:

Here is the method to connect with mysql:

const conn = mysql.createPool({
    connectionLimit: 10,
    host: config.host,
    user: config.user,
    password: config.password,
    database: 'shaw_elc_gst_13032019'
});

这是我console.log(conn)的结果:

This is the result when I console.log(conn):

Pool {
  _events:
   [Object: null prototype] {
     connection: [Function],
     acquire: [Function],
     enqueue: [Function],
     release: [Function],
     error: [Function] },
  _eventsCount: 5,
  _maxListeners: undefined,
  config:
   PoolConfig {
     acquireTimeout: 10000,
     connectionConfig:
      ConnectionConfig {
        host: 'localhost',
        port: 3306,
        localAddress: undefined,
        socketPath: undefined,
        user: 'root',
        password: '****',
        database: 'shaw_elc_gst_13032019',
        connectTimeout: 10000,
        insecureAuth: false,
        supportBigNumbers: false,
        bigNumberStrings: false,
        dateStrings: false,
        debug: undefined,
        trace: true,
        stringifyObjects: false,
        timezone: 'local',
        flags: '',
        queryFormat: undefined,
        pool: [Circular],
        ssl: false,
        multipleStatements: false,
        typeCast: true,
        maxPacketSize: 0,
        charsetNumber: 33,
        clientFlags: 455631 },
     waitForConnections: true,
     connectionLimit: 10,
     queueLimit: 0 },
  _acquiringConnections: [],
  _allConnections:
   [ PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11069,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11067,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11070,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11068,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11071,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11072,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11073,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11074,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11075,
       _pool: [Circular] },
     PoolConnection {
       _events: [Object],
       _eventsCount: 2,
       _maxListeners: undefined,
       config: [ConnectionConfig],
       _socket: [Socket],
       _protocol: [Protocol],
       _connectCalled: true,
       state: 'authenticated',
       threadId: 11076,
       _pool: [Circular] } ],
  _freeConnections: [],
  _connectionQueue:
   [ [Function],
     [Function],
     [Function],
     [Function],
     [Function],
     [Function],
     [Function],
     [Function] ],
  _closed: false }

推荐答案

我建议给汇集文档完整阅读.

您已经说过您正在使用conn.changeUser(/*...*/)，但是随后您已经说过您正在使用const conn = mysql.createPool(/*...*/);初始化该conn常量.这意味着conn是 pool ，而不是连接；没有changeUser方法也就不足为奇了.

You've said you're using conn.changeUser(/*...*/), but then you've said you're using const conn = mysql.createPool(/*...*/); to initialize that conn constant. That means conn is a pool, not a connection; it's not surprising that it doesn't have a changeUser method.

如果要更改数据库，则需要在连接而不是池上进行.您可以使用pool.getConnection/conn.changeUser/conn.query/conn.release代替速记pool.query形式.首先，调用变量pool，而不是conn:

If you want to change database, you need to do it on the connection, not the pool. Instead of using the shorthand pool.query form, you'd do pool.getConnection/conn.changeUser/conn.query/conn.release. First, call your variable pool, not conn:

const pool = mysql.createPool({

然后

pool.getConnection(function(err, conn) {
    if (err) {
        // handle/report error
        return;
    }
    conn.changeUser({
        database: req.session.dbname
    }, function (err) {
        if (err) {
            // handle/report error
            return;
        }
        // Use the updated connection here, eventually
        // release it:
        conn.release();
    });
});

话虽如此，如果是我，那么每个数据库都有一个连接池，而不是您在其中更改数据库的公共池时，我会感到更自在.就我而言，这可能纯粹是妄想症，但这是我会做的.但是，如果您不使用单独的池，建议您始终执行changeUser，这样可以确保您使用的是哪个数据库，或者完全测试 来查看mysql模块的作用.处理这个问题(并在模块的每个点发布上重复该测试，除非维护人员记录了该行为).

That said, if it were me, I'd be more comfortable having a connection pool per database, rather than a common pool where you change the database. That could be pure paranoia on my part, but it's what I'd do. But if you don't use separate pools, I suggest always do the changeUser so you're sure what database you're using, or test thoroughly to see what the mysql module does to handle this (and repeat that testing on every dot release of the module, unless the maintainer documents the behavior).

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