What Is It?

Join Monster is a JavaScript execution layer from GraphQL to SQL for batch data fetching for the Node.js graphql-js implementation. It's a function that takes a GraphQL query and dynamically translates GraphQL to SQL for efficient data retrieval, all in a single batch before resolution. It fetches only the data you need - nothing more, nothing less.

It solves the problem of making too many database queries, i.e. the "round-trip" problem or "N+1" problem, where the round-trips are requests for data over the TCP/IP stack between your API server and your SQL database. Think of it as an alternative to Facebook's DataLoader, but with more specificity toward SQL, making it more powerful and simpler to use with SQL.

It is NOT a tool for automatically creating a schema for you GraphQL from your database or vice versa. You retain the freedom and power to define your schemas how you want. Join Monster simply "compiles" a GraphQL query to a SQL query based on the existing schemas. It fits into existing applications and can be seamlessly removed later or used to varying degree. It's is a little opinionated, but not a full ORM.

Preview

Instead of writing the SQL yourself, you give Join Monster a bit of information about your SQL schema. It takes care of constructing the SQL query. Your queries can be as simple as this:

{                           SELECT                               {
  user(id: 1) {               "user"."id",                         user: {
    idEncoded                 "user"."first_name",                   idEncoded: 'MQ==',
    fullName        ==>       "user"."last_name",        ==>         fullName: 'andrew carlson',
    email                     "user"."email_address"                 email: 'andrew@stem.is'
  }                         FROM "accounts" AS "user"              }
}                           WHERE "user"."id" = 1                }

To something as complex as this:

{
  users {
    id, idEncoded, fullName, email
    following { id, fullName }
    comments {
      body
      author { id, fullName }
      post {
        id, body
        author { id, fullName }
      }
    }
  }
}

which becomes...

SELECT
  "users"."id" AS "id",
  "users"."first_name" AS "first_name",
  "users"."last_name" AS "last_name",
  "users"."email_address" AS "email_address",
  "following"."id" AS "following__id",
  "following"."first_name" AS "following__first_name",
  "following"."last_name" AS "following__last_name",
  "comments"."id" AS "comments__id",
  "comments"."body" AS "comments__body",
  "author"."id" AS "comments__author__id",
  "author"."first_name" AS "comments__author__first_name",
  "author"."last_name" AS "comments__author__last_name",
  "post"."id" AS "comments__post__id",
  "post"."body" AS "comments__post__body",
  "author$"."id" AS "comments__post__author$__id",
  "author$"."first_name" AS "comments__post__author$__first_name",
  "author$"."last_name" AS "comments__post__author$__last_name"
FROM accounts AS "users"
LEFT JOIN relationships AS "relationships" ON "users".id = "relationships".follower_id
LEFT JOIN accounts AS "following" ON "relationships".followee_id = "following".id
LEFT JOIN comments AS "comments" ON "users".id = "comments".author_id
LEFT JOIN accounts AS "author" ON "comments".author_id = "author".id
LEFT JOIN posts AS "post" ON "comments".post_id = "post".id
LEFT JOIN accounts AS "author$" ON "post".author_id = "author$".id

and responds with...

{
  "data": {
    "users": [
      {
        "id": 1,
        "idEncoded": "MQ==",
        "fullName": "andrew carlson",
        "email": "andrew@stem.is",
        "following": [
          {
            "id": 2,
            "fullName": "matt elder"
          }
        ],
        "comments": [
          {
            "body": "Wow this is a great post, Matt.",
            "author": {
              "id": 1,
              "fullName": "andrew carlson"
            },
            "post": {
              "id": 1,
              "body": "If I could marry a programming language, it would be Haskell.",
              "author": {
                "id": 2,
                "fullName": "matt elder"
              }
            }
          }
        ]
      },
      {
        "id": 2,
        "idEncoded": "Mg==",
        "fullName": "matt elder",
        "email": "matt@stem.is",
        "following": [],
        "comments": []
      }
    ]
  }
}

Demo

See it in action with this demo API.

Example

An API set up with Join Monster, both with and without Relay compliance.