Manually initializing a destroyed connection pool did not change database schema name

Summary

I am setting up test script to create multiple database schema to utilize AVA parallel test run. As a result, I need to create the schema first, then switch the application connection pool to use the new created schema. However I encountered a bug in doing so, and would like to ask the official proper way to change the database schema name.

Environment

Knex version: 0.21.0 Database + version: MySQL 5.7 OS: Windows 10

Bug

According to the documentation:

If you ever need to explicitly teardown the connection pool, you may use knex.destroy([callback]). You may use knex.destroy by passing a callback, or by chaining as a promise, just not both. To manually initialize a destroyed connection pool, you may use knex.initialize([config]), if no config is passed, it will use the first knex configuration used.

I expect I can change the database name by knex.destroy and knex.initialize(newConfig) with new configuration. This does not work.

Reduced test case as follows:

const knex = require('knex')

function getConfig () {
  return {
    client: 'mysql',
    connection: {
      host: 'localhost',
      user: 'root',
      password: ''
    }
  }
}

const db = knex(getConfig()).on('query', function (data) {
  console.log(data.sql)
})

const method = 1

;(async () => {
  // Randomly (in my case it is based on server listening port) assigned a database name for AVA parallel testing
  const dbName = 'TMP_DB_' + (Math.floor(Math.random() * 999) + 9001)
  try {
    await db.raw(`CREATE DATABASE ${dbName}`)
    await db.raw(`USE ${dbName}`)
    await db.schema.createTable('tmp1', (table) => {
      table.increments()
      table.string('val1', 10).notNullable()
    })
    if (method === 1) {
      // I tried the documented way, but the `connection.database` is not changed with the following code
      await db.destroy()
      const newConfig = getConfig()
      newConfig.connection.database = dbName
      db.initialize(newConfig)
    } else if (method === 2) {
      // Is this the proper way to set the `connection.database`?
      db.client.connectionSettings.database = dbName
    }
    // This will result in `Error: ER_NO_DB_ERROR: No database selected` if database name is not set
    await Promise.all([
      db('tmp1').insert({ val1: 'a' }),
      db('tmp1').insert({ val1: 'b' }),
      db('tmp1').insert({ val1: 'c' })
    ])
  } finally {
    try {
      await db.raw(`DROP DATABASE ${dbName}`)
    } catch (ignore) {}
    await db.destroy()
  }
  console.log('End')
})().catch(e => console.log(e.stack))

Question

My additional question together with this bug, is how to change the database schema of the connection pool? Is the const method = 2 the proper way to do so? Or it can only be treated as undocumented way and may change in the future?

[VeryCrazyDog]

@MehdiSaffar I haven’t thought of using Proxy at that time (maybe I didn’t even know Proxy at that time). Thanks a lot for sharing, though I am no longer working with project using RDBMS now.

[MehdiSaffar]

@VeryCrazyDog Here is a temporary approach with ES6 proxies you could use if you want, not sure how correct it is but it seems to work on my side. Example:

const defaultConfig = YOUR_KNEX_CONFIG

const makeKnex = require('knex')

const wrapper = { instance: makeKnex(defaultConfig) }

async function reconnect (config) {
  await wrapper.instance.destroy()
  wrapper.instance = makeKnex(config)
}

const knexInstance = new Proxy(wrapper, {
  get: (target, prop) => {
    if (prop === 'reconnect') {
      return reconnect
    }

    return target.instance[prop]
  }
})

module.exports = knexInstance