🦄 sequelize-find-unique

Finder for retrieving a single Sequelize model entry by a unique column or a unique combination of multiple columns. Queries that occur in the same tick and have the same where, attributes, and include parameters are automatically batched using a dataloader and will result in a single database query. This is very useful, especially on a GraphQL server to avoid the N+1 Problem.

This library is heavily inspired by Prisma's findUnique method.

Install

With npm:

npm install sequelize-find-unique

With Yarn:

yarn add sequelize-find-unique

How to use?

A findUnique function can be built for a specific Sequelize model by using the makeFindUnique function:

const { Sequelize, DataTypes } = require('sequelize');
const { makeFindUnique } = require('sequelize-find-unique');

const sequelize = new Sequelize('sqlite::memory:');

const User = sequelize.define('user', {
  id: { type: DataTypes.INTEGER, primaryKey: true, autoIncrement: true },
  username: { type: DataTypes.TEXT, unique: true },
});

const findUniqueUser = makeFindUnique(User);

// ...

// These queries have the same columns in the where parameter, so they are batched. Just one database query is executed
const users = await Promise.all([
  findUniqueUser({
    where: {
      username: 'john',
    },
  }),
  findUniqueUser({
    where: {
      username: 'mary',
    },
  }),
]);

The two findUniqueUser queries in the example are batched and only one database query is executed.

Using as model's static method

The findUnique (or name of your choice) static method can be defined for a model in the following way:

User.findUnique = makeFindUnique(User);

// ...

const user = await User.findUnique({
  where: {
    username: 'kalle',
  },
});

Attributes

Queries with the same attributes parameter are batched:

// These queries have the same attributes parameter, so they are batched. Just one database query is executed
const users = await Promise.all([
  User.findUnique({
    where: {
      username: 'john',
    },
    attributes: ['username'],
  }),
  User.findUnique({
    where: {
      username: 'mary',
    },
    attributes: ['username'],
  }),
]);

Note that, if the attributes parameter is provided, columns used in the where parameter must be present in the attributes parameter.

Associations

Queries with the same include parameter are batched:

// These queries have the same include parameter, so they are batched. Just one database query is executed
const users = await Promise.all([
  User.findUnique({
    where: {
      username: 'john',
    },
    include: { model: Comment },
  }),
  User.findUnique({
    where: {
      username: 'mary',
    },
    include: { model: Comment },
  }),
]);

Composite unique columns

Composite unique columns work just like a single unique column:

// These queries have the same columns in the where parameter, so they are batched. Just one database query is executed
const persons = await Promise.all([
  Person.findUnique({
    where: {
      firstName: 'Kalle',
      lastName: 'Ilves',
    },
  }),
  Person.findUnique({
    where: {
      firstName: 'John',
      lastName: 'Doe',
    },
  }),
]);

Custom serializers

Serializers can be used to customize the batching behavior. The serializeBatchKey option can be used to customize which queries go to the same batch. That is, queries that occur on the same tick will be batched based on the string key returned by the serializeBatchKey. The default serializeBatchKey serializer serializes the columns in the where parameter, the attributes parameter, and the include parameter.

The serielizeLoadKey option can be used to customize the DataLoader's cacheKeyFn function. The default serielizeLoadKey serializer serializes the where parameter.

Both functions receive the options provided for the findUnique function and should return a string. The serializeBatchKey and serializeLoadKey can be provided using the second argument, the options object, of the makeFindUnique function:

const customSerializeBatchKey = (options) => {
  return JSON.stringify(Object.keys(options.where));
};

const customSerializeLoadKey = (options) => {
  return JSON.stringify(options.where);
};

User.findUnique = makeFindUnique(User, {
  serializeBatchKey: customSerializeBatchKey,
  serializeLoadKey: customSerializeLoadKey,
});

Custom cache

The cache option can be used to provide a custom DataLoader cache implementation. The cache keys are strings and values DataLoader instances. The cache implementation should implement get, set, and delete methods:

class CustomCache {
  get(key) {
    // ...
  }

  set(key, value) {
    // ...
  }

  delete(key) {
    // ...
  }
}

User.findUnique = makeFindUnique(User, {
  cache: new CustomCache(),
});

The default cache implementation is a simple wrapper around Map.

TypeScript

The library is written in TypeScript, so types are on the house!

If you are using a static method like in the previous examples, just declare the method on your model class:

import { makeFindUnique, FindUniqueOptions } from 'sequelize-find-unique';

export class User extends Model<
  InferAttributes<User>,
  InferCreationAttributes<User>
> {
  declare id: CreationOptional<number>;
  declare username: string;

  declare static findUnique: (
    options: FindUniqueOptions<Attributes<User>>,
  ) => Promise<User | null>;
}

// ...

User.findUnique = makeFindUnique(User);