first commit

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Typescript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+

db/index.js

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+const db = require('sqlite');
+const _ = require('lodash');
+const faker = require('faker');
+const {getAllUsers, batchGetUsers, batchGetFollowers} = require('./queries');
+const setup = require('./setup');
+
+module.exports = {
+	initialize: setup,
+	batchGetUsers: batchGetUsers,
+	batchGetFollowers: batchGetFollowers,
+	getAllUsers: getAllUsers
+};
+
+

db/queries.js

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+const db = require('sqlite');
+const _ = require('lodash');
+const faker = require('faker');
+let dbQueries = 0;
+function logQuery(type) {
+	console.log('query', type, ++dbQueries);
+}
+
+async function batchGetFollowers(user_ids) {
+	logQuery('batchGetFollowers');
+	const rows = await db.all(`SELECT Persons.firstName, Persons.lastName, Persons.id, FollowerEdges.user_id as following_id 
+		FROM Persons 
+		INNER JOIN FollowerEdges WHERE FollowerEdges.follower_id = Persons.id 
+		AND FollowerEdges.user_id in (${user_ids.join(', ')})`)
+	const rowsGroupedByUserID = _.groupBy(rows, 'following_id');
+	return user_ids.map(id => rowsGroupedByUserID[id]);
+}
+
+async function batchGetUsers(user_ids) {
+	logQuery('batchGetUsers');
+	const rows = await db.all(`SELECT * from Persons WHERE id in (${user_ids.join(', ')})`);
+	const keyedRows = _.keyBy(rows, 'id');
+	return user_ids.map(id => keyedRows[id]);
+}
+
+async function getAllUsers() {
+	logQuery('getAllUsers');
+	return db.all(`SELECT * FROM Persons`);
+}
+
+
+
+module.exports = {
+	batchGetUsers: batchGetUsers,
+	batchGetFollowers: batchGetFollowers,
+	getAllUsers: getAllUsers
+};
+
+

db/setup.js

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+const db = require('sqlite');
+const _ = require('lodash');
+const faker = require('faker');
+let dbQueries = 0;
+async function createTables(db) {
+	await db.run(`
+		CREATE TABLE Persons (
+			id INTEGER PRIMARY KEY AUTOINCREMENT,
+			firstName TEXT,
+			lastName TEXT
+		);
+	`);
+
+	await db.run(`
+		CREATE TABLE FollowerEdges (
+			user_id NOT_NULL INTEGER,
+			follower_id NOT_NULL INTEGER,
+			FOREIGN KEY(user_id) REFERENCES Persons(id)
+			FOREIGN KEY(follower_id) REFERENCES Persons(id)
+			PRIMARY KEY(user_id,follower_id)
+		);
+	`)
+
+	return true;
+}
+
+async function mockData(db) {
+	let statement = await db.prepare(`INSERT INTO Persons (firstName, lastName) VALUES (?, ?)`);
+	_.range(9).forEach(i => statement.run(faker.name.firstName(), faker.name.lastName()));
+	await statement.finalize();
+	const rows = await db.all(`SELECT * FROM Persons`);
+	let edgesStatement = await db.prepare('INSERT INTO FollowerEdges (user_id, follower_id) VALUES (?, ?)');
+	rows.forEach(person => {
+		rows.filter(r => r.id !== person.id).forEach(personToFollow => {
+			edgesStatement.run(personToFollow.id, person.id);
+		})
+	});
+	await edgesStatement.finalize();
+
+}
+
+async function setupDB() {
+	await db.open(':memory:')
+	await createTables(db);
+	await mockData(db);
+	return Promise.resolve(true);
+	//let followers = await batchGetFollowers(db, [1, 2]);
+	//let users = await batchGetUsers(db, [1,2]);
+}
+
+module.exports = setupDB;
+
+

index.js

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+const express = require('express');
+const graphqlHTTP = require('express-graphql');
+const { buildSchema } = require('graphql');
+const db = require('./db')
+const DataLoader = require('dataloader');
+
+const userLoader = new DataLoader(async (keys) => {
+	const rows = await db.batchGetUsers(keys);
+	return rows.map(r => new User(r));
+});
+const followersLoader = new DataLoader(async (keys) => {
+	const rows = await db.batchGetFollowers(keys);
+	return rows.map(r => r.map(c =>new User(c)));
+});
+// Construct a schema, using GraphQL schema language
+var schema = buildSchema(`
+  type User {
+    firstName: String!
+    lastName: String!
+    followers: [User]
+  }
+
+  type Query {
+    users: [User]
+  }
+`);
+
+// This class implements the RandomDie GraphQL type
+class User {
+	constructor(data) {
+		this.id = data.id;
+		this.firstName = data.firstName;
+		this.lastName = data.lastName;
+	}
+
+	async followers(a, b, c) {
+		return followersLoader.load(this.id);
+		return followers;
+	}
+}
+
+// The root provides the top-level API endpoints
+var root = {
+  users: async function () {
+    const rows = await db.getAllUsers();
+		let result = rows.map(data => new User(data));
+		return result;
+  }
+}
+
+var app = express();
+app.use('/graphql', graphqlHTTP({
+  schema: schema,
+  rootValue: root,
+  graphiql: true,
+}));
+
+db.initialize().then(() => {
+	app.listen(4000);
+	console.log('Running a GraphQL API server at localhost:4000/graphql');
+});

package.json

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+{
+  "name": "graphql-dataloader-sqlite",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index"
+  },
+  "author": "",
+  "license": "ISC",
+  "dependencies": {
+    "dataloader": "^1.3.0",
+    "express": "^4.16.2",
+    "express-graphql": "^0.6.11",
+    "faker": "^4.1.0",
+    "graphql": "^0.11.7",
+    "lodash": "^4.17.4",
+    "sqlite": "^2.8.0",
+    "sqlite3": "^3.1.13"
+  }
+}