Optimizing queries on related tables in Sequelize

matteo.rebeschi :

I would like to know if there is a better way to obtain the following result: filtering a list of rows with values from table that's connected through a many-to-many relationship. In my example case, it's songs that feature certain instruments.

Here is my songs model:

module.exports = function(sequelize, DataTypes) {
    var Song = sequelize.define('songs', {
        id: {
            type: DataTypes.INTEGER(10).UNSIGNED,
            allowNull: false,
            primaryKey: true,
            autoIncrement: true
        },
        title: {
            type: DataTypes.STRING(50),
            allowNull: false
        },
    }, {
        tableName: 'songs',
        timestamps: false
    });

    Song.associate = function (models) {
        Song.belongsToMany(models.instruments, {through: 'songs_instruments', foreignKey: 'song_id'})
    };

    return Song
};

Here is my instruments model:

module.exports = function(sequelize, DataTypes) {
    var Instrument = sequelize.define('instruments', {
        id: {
            type: DataTypes.INTEGER(10).UNSIGNED,
            allowNull: false,
            primaryKey: true,
            autoIncrement: true
        },
        name: {
            type: DataTypes.STRING(50),
            allowNull: false
        }
    }, {
        tableName: 'instruments',
        timestamps: false,
    });

    Instrument.associate = function (models) {
        Instrument.belongsToMany(models.songs, {through: 'songs_instruments', foreignKey: 'instrument_id'})
    };

    return Instrument
};

Here is the model for the join table:

module.exports = function(sequelize, DataTypes) {
    return sequelize.define('songs_instruments', {
        id: {
            type: DataTypes.INTEGER(10).UNSIGNED,
            allowNull: false,
            primaryKey: true,
            autoIncrement: true
        },
        song_id: {
            type: DataTypes.INTEGER(10).UNSIGNED,
            allowNull: false,
            references: {
                model: 'songs',
                key: 'id'
            }
        },
        instrument_id: {
            type: DataTypes.INTEGER(10).UNSIGNED,
            allowNull: false,
            references: {
                model: 'instruments',
                key: 'id'
            }
        }
    }, {
        tableName: 'songs_instruments',
        timestamps: false
    });
};

And here is the way I am currently doing my fetching (args['instruments'] contains a list of the instruments I want to filter the songs for):

const instruments = await db.instruments.findAll({
    where: {name: args['instruments']}
})

const songs_instruments = await db.songs_instruments.findAll({
    where: {instrument_id: instruments.map(instrument => instrument.id)}
})

const songs = await db.songs.findAll({
    where: {id: songs_instruments.map(song => song.song_id)}
})
return songs

While this works correctly, and in the end I get the results that I expect, I can't help but wonder if there is a more efficient way of querying the database, as doing it like this causes a total of three queries to be executed:

Executing (default): SELECT `id`, `name` FROM `instruments` AS `instruments` WHERE `instruments`.`name` IN ('Vocals', 'Trumpet', 'Guitar');
Executing (default): SELECT `id`, `song_id`, `instrument_id` FROM `songs_instruments` AS `songs_instruments` WHERE `songs_instruments`.`instrument_id` IN (1, 3, 7);
Executing (default): SELECT `id`, `title` FROM `songs` AS `songs` WHERE `songs`.`id` IN (1, 1, 2, 2, 3, 3);

I am quite new to Sequelize, hence my probably incorrect/suboptimal way of achieving my goal.

Greg Belyea :

Oh i totally missed that.. it was late.. yes you can do that.. add the as like below to alias this connection, and do the same in songs with as: 'instruments'... you don't need to fetch the join records..

Instrument.associate = function (models) {
        Instrument.belongsToMany(models.songs, {through: 'songs_instruments', as: 'songs', foreignKey: 'instrument_id', otherKey: 'song_id'})
    };

const instruments = await db.instruments.findAll({
    where: {name: args['instruments']},
    {
     include: [{
        model: db.songs,
        as: 'songs', 
        through: db.songs_instruments,
      }]
   }
});

OR Something along the lines of the include below...

const songs = await db.songs.findAll({
          include: [{
            model: db.instruments,
            as: 'instruments', 
            through: db.songs_instruments,
            where: {name: args['instruments']}
          }],
        });