Can we express GENERATED COLUMN added INDEX with schema file ( MySQL )

What was unclear.

Can we express GENERATED COLUMN added INDEX with schema file ? We want to express below SQL to Sequelize schema file.

CREATE TABLE jsontable (
  id INTEGER,
  json_data JSON,
 # ✅ Generated Column
  user_id INTEGER GENERATED ALWAYS AS (json_unquote(json_extract(`json_data`,'$.user_id'))) VIRTUAL,  
  PRIMARY KEY(id)
  );
 INSERT INTO jsontable(id, json_data) VALUES(1, '{"name": "Kevin", "user_id": "111"}');
 INSERT INTO jsontable(id, json_data) VALUES(2, '{"name": "Jonh", "user_id": "222"}');
 ALTER TABLE jsontable ADD INDEX (user_id);  # ✅ ADD INDEX into GENERATED COLUMN

/**
 * Test Table
 * @param {Sequelize} sequelize instance
 * @param {*} DataTypes data types
 */
module.exports = (sequelize, DataTypes) => {
  const JsonTests = sequelize.define('JsonTests', {
    id: {
      type: DataTypes.INTEGER.UNSIGNED,
      primaryKey: true,
    },
    json_data: {
      type: DataTypes.JSON,
      allowNull: false,
    },
// ---- ↓WE WANT TO EXPRESS GENERATED COLUMN↓ HOW TO? ----
    user_id: {
      type: DataTypes.INTEGER.UNSIGNED,
      allowNull: false,
    },
  }, {
   // Options...
    tableName: 'json_tests',
    timestamps: true,
    charset: 'utf8',
    indexes: [
        {unique: false, fields: ['id']},
// ---- ↓WE WANT TO ADD INDEX TO user_id ↓HOW TO? ----
        {unique: false, fields: ['user_id']},
     ]
  });

  return JsonTests;
};

I’m looking for information from the document, but because I couldn’t find it, I made an issue. It would be nice if you could tell me if you know.

[malyzeli]

I’m also in need of GENERATED columns support, since defining column as autoIncrement does not automatically prevent explicit value insertion, which can cause problems…

See those two questions and aswers on Stack Overflow for detailed explanation:

• Postgres autoincrement not updated on explicit id inserts
• PostgreSQL serial vs identity

I am not sure if this is related to Postgres only, but it would be nice to support this feature anyway.

As a quick workaround you can remove id values using beforeCreate hook, but unfortunately you have to define that for every single model individually…

const ignoreField = field => (entity, options) => {
  options.fields = options.fields.filter(col => col !== field);
};

database.define(
  "user",
  {
    id: {
      type: Sequelize.INTEGER,
      allowNull: false,
      autoIncrement: true,
      primaryKey: true,
    },
  },
  {
    hooks: {
      beforeCreate: ignoreField("id"),
    },
  }
);

I did a quick search through the repository and there does not seem to be any implementation of GENERATED ALWAYS query (you can see results here), so I suppose it’s not possible to define that in the model. You can probably create such column using raw SQL query, but that’s not an ideal solution.

It would be nice if Sequelize could at least automatically remove values for autoIncrement columns before passing entity data to the query builder, as shown in my code snipped above.

I might try to write a plugin for that, but unfortunately I didn’t find any official documentation on writing plugins…

Will appreciate if anybody can give some hints or at least point us in the right direction!

[papb]

Currently there is no guideline as for how to write a plugin, but I think that would be a great thing to have. Maybe I can look into it in the future.

For this, check sequelize/website#296. Short story: this was discussed in the past but nothing was decided…