Knex.md

Using DataLoader with Knex.js

This example demonstrates how to use DataLoader with SQL databases via Knex.js, which is a SQL query builder and a client for popular databases such as PostgreSQL, MySQL, MariaDB etc.

Similarly to the SQL example, you can use "where in" clause to fetch multiple records by the list of IDs with the only difference that you don't have to write any SQL code by hand.

const DataLoader = require('dataloader');
const db = require('./db'); // an instance of Knex client

// The list of data loaders

const loaders = {
  user: new DataLoader(ids =>
    db
      .table('users')
      .whereIn('id', ids)
      .select()
      .then(rows => ids.map(id => rows.find(x => x.id === id))),
  ),

  story: new DataLoader(ids =>
    db
      .table('stories')
      .whereIn('id', ids)
      .select()
      .then(rows => ids.map(id => rows.find(x => x.id === id))),
  ),

  storiesByUserId: new DataLoader(ids =>
    db
      .table('stories')
      .whereIn('author_id', ids)
      .select()
      .then(rows => ids.map(id => rows.filter(x => x.author_id === id))),
  ),
};

// Usage

const [user, stories] = await Promise.all([
  loaders.user.load('1234'),
  loaders.storiesByUserId.load('1234'),
]);

For a complete example visit kriasoft/nodejs-api-starter.