db2graphql

db2graphql

Generates a Graphql schema and resolvers from an existing relational database

:exclamation::exclamation::exclamation: Warning: don't use this in production yet, but your feedback is very important!

Features

• Fully compatible with express, koa, hapi and Apollo Server
• Converts an existing relational database (only PostgreSQL for now) schema to a JSON schema
• Generates a Graphql schema (string) with few but convenient types, queries and mutations
• Implements a generic Graphql resolver ready for API prototyping
• Eager loading of related records based on foreign keys
• Allows to add/override resolvers

Demo

Query example

query{
  getFirstOfUsers(
    filter: "users:id=2"
    pagination: "posts:limit=10;orderby=title desc"
  ) {
    id
    username
    posts {
      id
      title
      categories {
        id
        title
      }
    }
  }
}

Limitations/TODO

• Only PostgreSQL supported
• Better database types handling
• Better database queries optimization
• Create tests
• Create an NPM module
• Move to TypeScript
• Add more and improve convenient API methods. Currently, only:
  1. getPage
  2. getFirstOf
  3. putItem

Usage

Generate a Graphql schema from an existing relational database

const knex = require('knex');
const db2g = require('db2graphql');
const api = new db2g(knex(require('./connection.json')));
await api.connect();
const schema = api.getSchema();

Example of file connection.json

{
  "client": "pg",
  "version": "10.6",
  "debug": false,
  "connection": {
    "host" : "127.0.0.1",
    "user" : "postgres",
    "password" : "postgres",
    "database" : "db2graphql"
  },
  "exclude": []
}

Complete example with Apollo Server

const knex = require('knex');
const db2g = require('db2graphql');
const { ApolloServer, gql } = require('apollo-server');

const start = async (cb) => {

  /**************************************/
  const api = new db2g(knex(require('./connection.json')));
  await api.connect(); // Connects to database and extracts database schema
  const schema = api.getSchema();
  const resolvers = api.getResolvers();
  /**************************************/

  // Create Apollo Server and start
  if (!schema) throw new Error('Error: empty schema');
  console.log(schema);
  const server = new ApolloServer({
    typeDefs: gql`${schema}`,
    resolvers,
  });
  server.listen().then(({ url }) => {
    console.log(`🚀 Server ready at ${url}`);
  });
}

start();

Implement specific resolvers

api.override('getFirstOf', async (root, args, context) => {
  const { resolver, tablename, db } = context.ioc;
  if (tablename === 'categories') return await db('categories').first();

   // You can still run the build-in resolver
  return resolver.getFirstOf(tablename, args);
});

Example without database connection

const db2g = require('db2graphql');
const api = new db2g();

// Add a query and resolver
api.addQuery('getFoo: Boolean');
api.addResolver('Query', 'getFoo', async (root, args, context) => {
  return true;
});

// Ready to generate schema
const schema = api.getSchema();
const resolvers = api.getResolvers();

Run de demo

$ git clone https://github.com/taviroquai/db2graphql.git
$ cd db2graphql
$ npm install
$ psql -h localhost -U postgres -c "CREATE DATABASE db2graphql"
$ cp demo/connection.example.json demo/connection.json
# Edit demo/connection.json
$ npm run demo-db
$ npm run start

Open browser on http://localhost:4000 and see your Graphql API ready!

Collab

Anyone is free to collab :)

License

MIT, what else?