Machine Learning Data Science Meetup | 10.07.2018 | #AperiTech

1. GraphQL ♥ Graph Database
15/03/2018

2. Marco Liberati
@dej611
Enrico Risa
@wolf4ood

3. Agenda
- GraphQL Introduction
- GraphQL Schema Definition (Meetup)
- Why GraphQL ♥ Graph Database?
- Schema Impl with a GraphDB

4. WHY GRAPHQL?

5. Let’s Talk About Rest first
● Resource Based
● HTTP Verbs
○ GET
○ PUT
○ PATCH
○ DELETE
○ POST
Actions -> Verbs + Uris

6. Meetup model with REST
● https://api.meetup.com/:urlname
● https://api.meetup.com/:urlname/members
● https://api.meetup.com/:urlname/events
● https://api.meetup.com/:urlname/events/:event_id/rsvp

7. Sounds Cool, Let’s Use it

8. Multiple Round Trips Problem

9. How Do we Handle That?
GET /GraphRM?fields=topics

10. …And What about Over-fetching?
GET /GraphRM?only=id,name
I need only those fields

11. You will probably end up with some custom
endpoints

12. API Documentation
● How can i use those APIs ?
● What parameters this endpoint support?
● Is this parameter required?
● Swagger
● JSON Schema
● JSON:API
● API Blueprint
Documentation should be good in order to let
people use our APIs without headache

13. Potential Problems
● Multiple Round trips
● Over/Under fetching
● Documentation

15. What GraphQL IS NOT..
● A query language for Graph Databases
● Database / Storage Engine
● A library
● It’s not language specific

16. What Is IT ?
GraphQL is a query language for APIs and a runtime for fulfilling those queries
with your existing data. GraphQL provides a complete and understandable
description of the data in your API, gives clients the power to ask for exactly what
they need and nothing more, makes it easier to evolve APIs over time, and
enables powerful developer tools.

17. Just a spec
● A declarative query language
● A type system
● A runtime that fetch and mutate data

18. Hello GraphQL

19. Hello GraphQL (with nesting)

20. How does it work ?
● The server describe what is possible (a type system)
● The client can asks exactly what data it requires
● The server then gives back results with the same shape as the query
Power to the client

21. Powerful Type System
● Hierarchical
● Strongly-Typed
● Self Documenting
● Enable Introspection
● Client-specified queries

22. Types
● Objects
● Scalar
○ Boolean
○ Int
○ Float
○ String
○ Custom Types
● Enums
● Lists
● Unions
● Interfaces

23. GraphQL Schema Language
● GraphQL type system
● Describes what data can be queried
● Language-agnostic

24. GraphQL Schema Language Example

25. Mutation

26. Introspection

27. … Enables Tools
● GraphiQL
● Documentation
● IDE plugins
● Code generation
● Client Side Validation
● …

28. GraphQL Schema Definition (Meetup)
● Entity
○ User
○ Meetup
○ Tag
○ Event
● Query
○ meetupsByName
○ usersByName

29. GraphQL Schema Definition (Meetup)
Demo time!
https://github.com/GraphRM/graphql-graphdb

30. Why GraphQL ♥ Graph Database?

31. A GraphQL query represents a description of a relationship:
Why GraphQL ♥ Graph Database?
Person “me”
:id
:name
Person
:name
Person
:name

32. A GraphQL query represents a description of a relationship:
Why GraphQL ♥ Graph Database?
Person “me”
:id
:name
Person
:name
Person
:name
Problem:
● For each Person the GraphQL
reducer will go to the database and
ask for data.
● This is known as the N+1 query
problem.
● Which in turns mean poor
performance

33. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?
● This could prevent the N+1 queries problem
● A GraphDB is designed to run traversals
● Bonus: if the schema is the same for both GraphQL and DB that is a
huge win!

34. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?

35. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?

36. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?
● This is still a PoC but the idea is:
○ Parse the Schema and the query
○ Traverse the query and build a database query

37. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?
This is not fully compatible yet but there are some PoC:
● GraphQL -> Neo4J Cypher:
https://github.com/neo4j-graphql/neo4j-graphql-js
● GraphQL -> OrientDB Gremlin + MATCH
https://github.com/kensho-technologies/graphql-compiler

38. What if we could translate one GraphQL query to a single GraphDB query?
Why GraphQL ♥ Graph Database?
Demo time!
https://github.com/GraphRM/graphql-graphdb

39. Grazie :)

40. Resources
● GraphQL: http://graphql.org/learn/
● AST Explorer: https://astexplorer.net/
● GRANDstack: https://grandstack.io/
● GraphQL + OrientDB:
https://blog.kensho.com/compiled-graphql-as-a-database-query-language-72e1
06844282
● GraphQL + Neo4J: https://neo4j.com/developer/graphql/
● Five common pitfalls with GraphQL and how Neo4J-GraphQL aims to solve
them:
https://blog.grandstack.io/five-common-graphql-problems-and-how-neo4j-graph
ql-aims-to-solve-them-e9a8999c8d43