NodeJS/Sequelize/MySQL - Why postgres dependencies are needed?

Question

I'm new to Node and Sequelize and I'm facing a problem with establishing connection to MySQL database. I wonder why Postgres dependencies are needed even if set the dialect to mysql one. I would be grateful if you can help me to point the problem.

From packages.json

"dependencies": {
    // ...
    "mysql2": "1.1.2",
    "sequelize": "3.27.0"
},

The way I'm trying to connect db:

var Sequelize = require('sequelize');

var sequelize = new Sequelize('dbName', 'dbUser', 'dbPass', {
    host: 'localhost',
    dialect: 'mysql'
});

sequelize.authenticate()
    .then(function(err) {
        console.log('Connection has been established successfully.');
    })
    .catch(function (err) {
        console.log('Unable to connect to the database:', err);
    });

The error I'm facing:

Failed to compile.

Error in ./~/sequelize/lib/dialects/postgres/hstore.js
Module not found: 'pg-hstore' in ~/node_modules/sequelize/lib/dialects/postgres
@ ./~/sequelize/lib/dialects/postgres/hstore.js 3:13-33

---

UPDATE 1 (sequelize init command used)

From models/index.js:

'use strict';

var fs        = require('fs');
var path      = require('path');
var Sequelize = require('sequelize');
var basename  = path.basename(module.filename);
var env       = 'development'; //process.env.NODE_ENV || 'development';
var config    = require(__dirname + '/../config/config.json')[env];
var db        = {};

if (config.use_env_variable) {
  var sequelize = new Sequelize(process.env[config.use_env_variable]);
} else {
  var sequelize = new Sequelize(config.database, config.username, config.password, config);
}

fs
  .readdirSync(__dirname)
  .filter(function(file) {
    return (file.indexOf('.') !== 0) && (file !== basename) && (file.slice(-3) === '.js');
  })
  .forEach(function(file) {
    var model = sequelize['import'](path.join(__dirname, file));
    db[model.name] = model;
  });

Object.keys(db).forEach(function(modelName) {
  if (db[modelName].associate) {
    db[modelName].associate(db);
  }
});

db.sequelize = sequelize;
db.Sequelize = Sequelize;

module.exports = db;

And my config/config.json:

{
  "development": {
    "username": "dbUser",
    "password": "dbPassword",
    "database": "dbName",
    "host": "127.0.0.1",
    "dialect": "mysql2"
  },
  "test": {
    "username": "root",
    "password": null,
    "database": "database_test",
    "host": "127.0.0.1",
    "dialect": "mysql2"
  },
  "production": {
    "username": "root",
    "password": null,
    "database": "database_production",
    "host": "127.0.0.1",
    "dialect": "mysql2"
  }
}

---

UPDATE 2

Now I see I have an additional message:

Error: The dialect mysql is not supported. (Error: Cannot find module './mysql'.)

However, I have it installed in to root of the node_modules directory.

---

UPDATE 3

The steps I take to reproduce the problem:

• create-react-app tmpApp
• npm install --save mysql sequelize
• npm install -g sequelize-cli
• sequelize init
• add to src/index.js: var models = require('../models')
• npm start - the problem appears

---

UPDATE 4 - Problem resolved

First of all really thanks for your help! The problem actually occurred because I was trying to mix server and client sides into one application (I was just playing). The Sequelize and the mysql modules itself do not seem to work on the browser environment. When the server side is placed outside the react-app everything behaves as expected.

Answer 1

In your database config, you must have set the config as something else to be used.

1. Check the env using sequelize. Usually, it's a config.json file inside your database directory.
2. Change the dialect to mysql2 since that's what you want to use.

Answer 2

To solve your problem do:

`npm install mysql ---save` instead of `mysql2`

that will get your code working. And from what i saw in offical docs here they seem to support mysql2 as well but it doesn't work. As i have tested and got similar results. I will suggest raise a issue in their github so they can fix it their. You can do so here