Field with type Sequelize.JSON returns string when MySQL dialect is used for a MariaDB database

What are you doing?

When querying a model, which has a field with type sequelize.JSON, it returns JSON string instead of parsed JS object for that field.

// dbService.js
// Connecting to DB, params are coming from config file
export const databaseService = new Sequelize(database, user, password, {
  host,
  port,
  dialect: 'mysql',
  logging,
  operatorsAliases: Sequelize.Op,
  define: {
    freezeTableName: true,
    charset,
    collate,
  },
});

// models/index.js
// Creating the models
import fs from 'fs';
import path from 'path';
import sequelize from 'sequelize';
import { databaseService } from 'utils/database/dbService';

const basename = path.basename(__filename);
const db = {};

fs.readdirSync(__dirname)
  .filter((file) => {
    return !file.startsWith('.') && file !== basename && file !== 'index.js' && file.slice(-3) === '.js';
  })
  .forEach((file) => {
    const fileName = path.join(__dirname, file);
    const model = require(fileName).default(databaseService, sequelize);
    db[model.name] = model;
  });

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

db.sequelize = databaseService;
export default db;

// models/Test.js
// Creating a Test model
export default (dbService, sequelize) => {
  const Test = dbService.define('Test', {
    id: {
      type: sequelize.UUID,
      defaultValue: sequelize.UUIDV1,
      primaryKey: true,
    },

    data: {
      type: sequelize.JSON,
    },
  });

  return Test;
};

// test.js
// Usage in test script
import './models';
import { databaseService } from './dbService';

const newTest = await db.models.Test.create({
  data: { x: 1 }
});
console.log('check 1', typeof newTest.data);  // check1 object

const test = await db.models.Test.findOne({ id: newTest.id });
console.log('check 2', typeof test.data);  // check 2 string
console.log('check 3', typeof test.get('data')); // check 3 string

To Reproduce Steps to reproduce the behavior:

1. As you can see above, I’m connecting to my DB and creating model Test, which has two fields: id and data. The latter one is of type sequelize.JSON.
2. Then in my test script, I create an instance of Test model, providing JS object for data field. On the next line when I print type of data, it prints correctly object.
3. However, when I query that object using findOne (no difference how you query), the returned object’s data field is string now.

What do you expect to happen?

I expect to get a parsed JS object out of my JSON field.

What is actually happening?

I’m getting JSON string instead of object.

Environment

Dialect:

• mysql
• postgres
• sqlite
• mssql
• any

Dialect library version: mysql2 - 1.6.4 Database version: mysql Ver 15.1 Distrib 10.3.14-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2 (The DB is run in Docker using official MariaDB image) Sequelize version: 4.41.2 Node Version: v10.15.2 OS: macOS Mojave, 10.14.3 (18D109) Tested with latest release:

• No
• Yes, specify that version:

[omegascorp]

Looks the issue is only partially fixed in mariadb driver.

Where you read records from MariaDB via mariadb driver, Sequelize provides JSON values as objects, but if you use include, subitem JSON fields are provided as strings.

Here is a code snippet:

const User = dbService.define(
  'User',
  {
    id: {
      type: sequelize.INTEGER,
      primaryKey: true,
    },
    data: {
      type: sequelize.JSON,
      defaultValue: '',
    },
  },
);

const Project = dbService.define(
  'Project',
  {
    id: {
      type: sequelize.INTEGER,
      primaryKey: true,
    },
    data: {
      type: sequelize.JSON,
      defaultValue: '',
    },
  },
);

Project.belongsTo(User);
User.hasMany(Project, {
  foreignKey: 'userId',
  as: 'projects',
});

(async () => {
  const users = await User.findAll({
    include: [
      {
        model: Project,
        as: 'projects',
      },
    ],
    attributes: ['id', 'data', 'projects.id', 'projects.data']
  });
  console.info(typeof users[0].data); // object
  console.info(typeof users[0].projects[0].data); // string
})();

See a working demo here: https://github.com/omegascorp/sequelize-mariadb-json-test

[misos1]

@papb

• MySQL dialect + MariaDB database - string
• MySQL dialect + MySQL database - object
• MariaDB dialect + MariaDB database - object