super-graph/docs/website/docs/graphql.md

id	title	sidebar_label
graphql	How to GraphQL	GraphQL Syntax

GraphQL (GQL) is a simple query syntax that's fast replacing REST APIs. GQL is great since it allows web developers to fetch the exact data that they need without depending on changes to backend code. Also if you squint hard enough it looks a little bit like JSON 😃

The below query will fetch an users name, email and avatar image (renamed as picture). If you also need the users id then just add it to the query.

query {
  user {
    full_name
    email
    picture: avatar
  }
}

Multiple tables can also be fetched using a single GraphQL query. This is very fast since the entire query is converted into a single SQL query which the database can efficiently run.

query {
  user {
    full_name
    email
  }
  products {
    name
    description
  }
}

Fetching data

To fetch a specific product by it's ID you can use the id argument. The real name id field will be resolved automatically so this query will work even if your id column is named something like product_id.

query {
  products(id: 3) {
    name
  }
}

Postgres also supports full text search using a TSV index. Super Graph makes it easy to use this full text search capability using the search argument.

query {
  products(search: "ale") {
    name
  }
}

Fragments

Fragments make it easy to build large complex queries with small composible and re-usable fragment blocks.

query {
  users {
    ...userFields2
    ...userFields1
    picture_url
  }
}

fragment userFields1 on user {
  id
  email
}

fragment userFields2 on user {
  first_name
  last_name
}

Sorting

To sort or ordering results just use the order_by argument. This can be combined with where, search, etc to build complex queries to fit you needs.

query {
  products(order_by: { cached_votes_total: desc }) {
    id
    name
  }
}

Filtering

Super Graph support complex queries where you can add filters, ordering,offsets and limits on the query. For example the below query will list all products where the price is greater than 10 and the id is not 5.

query {
  products(where: { and: { price: { gt: 10 }, not: { id: { eq: 5 } } } }) {
    name
    price
  }
}

Nested where clause targeting related tables

Sometimes you need to query a table based on a condition that applies to a related table. For example say you need to list all users who belong to an account. This query below will fetch the id and email or all users who belong to the account with id 3.

query {
  users(where: {
      accounts: { id: { eq: 3 } }
    }) {
    id
    email
  }
}`

Logical Operators

Name	Example	Explained
and	price : { and : { gt: 10.5, lt: 20 }	price > 10.5 AND price < 20
or	or : { price : { greater_than : 20 }, quantity: { gt : 0 } }	price >= 20 OR quantity > 0
not	not: { or : { quantity : { eq: 0 }, price : { eq: 0 } } }	NOT (quantity = 0 OR price = 0)

Other conditions

Name	Example	Explained
eq, equals	id : { eq: 100 }	id = 100
neq, not_equals	id: { not_equals: 100 }	id != 100
gt, greater_than	id: { gt: 100 }	id > 100
lt, lesser_than	id: { gt: 100 }	id < 100
gte, greater_or_equals	id: { gte: 100 }	id >= 100
lte, lesser_or_equals	id: { lesser_or_equals: 100 }	id <= 100
in	status: { in: [ "A", "B", "C" ] }	status IN ('A', 'B', 'C)
nin, not_in	status: { in: [ "A", "B", "C" ] }	status IN ('A', 'B', 'C)
like	name: { like "phil%" }	Names starting with 'phil'
nlike, not_like	name: { nlike "v%m" }	Not names starting with 'v' and ending with 'm'
ilike	name: { ilike "%wOn" }	Names ending with 'won' case-insensitive
nilike, not_ilike	name: { nilike "%wOn" }	Not names ending with 'won' case-insensitive
similar	name: { similar: "%(b|d)%" }	Similar Docs
nsimilar, not_similar	name: { nsimilar: "%(b|d)%" }	Not Similar Docs
has_key	column: { has_key: 'b' }	Does JSON column contain this key
has_key_any	column: { has_key_any: [ a, b ] }	Does JSON column contain any of these keys
has_key_all	column: [ a, b ]	Does JSON column contain all of this keys
contains	column: { contains: [1, 2, 4] }	Is this array/json column a subset of value
contained_in	column: { contains: "{'a':1, 'b':2}" }	Is this array/json column a subset of these value
is_null	column: { is_null: true }	Is column value null or not

Aggregations

You will often find the need to fetch aggregated values from the database such as count, max, min, etc. This is simple to do with GraphQL, just prefix the aggregation name to the field name that you want to aggregrate like count_id. The below query will group products by name and find the minimum price for each group. Notice the min_price field we're adding min_ to price.

query {
  products {
    name
    min_price
  }
}

Name	Explained
avg	Average value
count	Count the values
max	Maximum value
min	Minimum value
stddev	Standard Deviation
stddev_pop	Population Standard Deviation
stddev_samp	Sample Standard Deviation
variance	Variance
var_pop	Population Standard Variance
var_samp	Sample Standard variance

All kinds of queries are possible with GraphQL. Below is an example that uses a lot of the features available. Comments # hello are also valid within queries.

query {
  products(
    # returns only 30 items
    limit: 30

    # starts from item 10, commented out for now
    # offset: 10,

    # orders the response items by highest price
    order_by: { price: desc }

    # no duplicate prices returned
    distinct: [price]

    # only items with an id >= 30 and < 30 are returned
    where: { id: { and: { greater_or_equals: 20, lt: 28 } } }
  ) {
    id
    name
    price
  }
}

Custom Functions

Any function defined in the database like the below add_five that adds 5 to any number given to it can be used within your query. The one limitation is that it should be a function that only accepts a single argument. The function is used within you're GraphQL in similar way to how aggregrations are used above. Example below

query {
  thread(id: 5) {
    id
    total_votes
    add_five_total_votes
  }
}

Postgres user-defined function add_five

CREATE OR REPLACE FUNCTION add_five(a integer) RETURNS integer AS $$
BEGIN

    RETURN a + 5;
END;
$$ LANGUAGE plpgsql;

In GraphQL mutations is the operation type for when you need to modify data. Super Graph supports the insert, update, upsert and delete. You can also do complex nested inserts and updates.

When using mutations the data must be passed as variables since Super Graphs compiles the query into an prepared statement in the database for maximum speed. Prepared statements are are functions in your code when called they accept arguments and your variables are passed in as those arguments.

Insert

{
  "data": {
    "name": "Art of Computer Programming",
    "description": "The Art of Computer Programming (TAOCP) is a comprehensive monograph written by computer scientist Donald Knuth",
    "price": 30.5
  }
}

mutation {
  product(insert: $data) {
    id
    name
  }
}

Bulk insert

{
  "data": [
    {
      "name": "Art of Computer Programming",
      "description": "The Art of Computer Programming (TAOCP) is a comprehensive monograph written by computer scientist Donald Knuth",
      "price": 30.5
    },
    {
      "name": "Compilers: Principles, Techniques, and Tools",
      "description": "Known to professors, students, and developers worldwide as the 'Dragon Book' is available in a new edition",
      "price": 93.74
    }
  ]
}

mutation {
  product(insert: $data) {
    id
    name
  }
}

Update

{
  "data": {
    "price": 200.0
  },
  "product_id": 5
}

mutation {
  product(update: $data, id: $product_id) {
    id
    name
  }
}

Bulk update

{
  "data": {
    "price": 500.0
  },
  "gt_product_id": 450.0,
  "lt_product_id:": 550.0
}

mutation {
  product(
    update: $data
    where: { price: { gt: $gt_product_id, lt: lt_product_id } }
  ) {
    id
    name
  }
}

Delete

{
  "data": {
    "price": 500.0
  },
  "product_id": 5
}

mutation {
  product(delete: true, id: $product_id) {
    id
    name
  }
}

Bulk delete

{
  "data": {
    "price": 500.0
  }
}

mutation {
  product(delete: true, where: { price: { eq: { 500.0 } } }) {
    id
    name
  }
}

Upsert

{
  "data": {
    "id": 5,
    "name": "Art of Computer Programming",
    "description": "The Art of Computer Programming (TAOCP) is a comprehensive monograph written by computer scientist Donald Knuth",
    "price": 30.5
  }
}

mutation {
  product(upsert: $data) {
    id
    name
  }
}

Bulk upsert

{
  "data": [
    {
      "id": 5,
      "name": "Art of Computer Programming",
      "description": "The Art of Computer Programming (TAOCP) is a comprehensive monograph written by computer scientist Donald Knuth",
      "price": 30.5
    },
    {
      "id": 6,
      "name": "Compilers: Principles, Techniques, and Tools",
      "description": "Known to professors, students, and developers worldwide as the 'Dragon Book' is available in a new edition",
      "price": 93.74
    }
  ]
}

mutation {
  product(upsert: $data) {
    id
    name
  }
}

Often you will need to create or update multiple related items at the same time. This can be done using nested mutations. For example you might need to create a product and assign it to a user, or create a user and his products at the same time. You just have to use simple json to define you mutation and Super Graph takes care of the rest.

Nested Insert

Create a product item first and then assign it to a user

{
  "data": {
    "name": "Apple",
    "price": 1.25,
    "created_at": "now",
    "updated_at": "now",
    "user": {
      "connect": { "id": 5 }
    }
  }
}

mutation {
  product(insert: $data) {
    id
    name
    user {
      id
      full_name
      email
    }
  }
}

Or it's reverse, create the user first and then his product

{
  "data": {
    "email": "thedude@rug.com",
    "full_name": "The Dude",
    "created_at": "now",
    "updated_at": "now",
    "product": {
      "name": "Apple",
      "price": 1.25,
      "created_at": "now",
      "updated_at": "now"
    }
  }
}

mutation {
  user(insert: $data) {
    id
    full_name
    email
    product {
      id
      name
      price
    }
  }
}

Nested Update

Update a product item first and then assign it to a user

{
  "data": {
    "name": "Apple",
    "price": 1.25,
    "user": {
      "connect": { "id": 5 }
    }
  }
}

mutation {
  product(update: $data, id: 5) {
    id
    name
    user {
      id
      full_name
      email
    }
  }
}

Or it's reverse, update a user first and then his product

{
  "data": {
    "email": "newemail@me.com",
    "full_name": "The Dude",
    "product": {
      "name": "Banana",
      "price": 1.25
    }
  }
}

mutation {
  user(update: $data, id: 1) {
    id
    full_name
    email
    product {
      id
      name
      price
    }
  }
}

Pagination

This is a must have feature of any API. When you want your users to go through a list page by page or implement some fancy infinite scroll you're going to need pagination. There are two ways to paginate in Super Graph.

Limit-Offset This is simple enough but also inefficient when working with a large number of total items. Limit, limits the number of items fetched and offset is the point you want to fetch from. The below query will fetch 10 results at a time starting with the 100th item. You will have to keep updating offset (110, 120, 130, etc ) to walk thought the results so make offset a variable.

query {
  products(limit: 10, offset: 100) {
    id
    slug
    name
  }
}

Cursor

This is a powerful and highly efficient way to paginate a large number of results. Infact it does not matter how many total results there are this will always be lighting fast. You can use a cursor to walk forward or backward through the results. If you plan to implement infinite scroll this is the option you should choose.

When going this route the results will contain a cursor value this is an encrypted string that you don't have to worry about just pass this back in to the next API call and you'll received the next set of results. The cursor value is encrypted since its contents should only matter to Super Graph and not the client. Also since the primary key is used for this feature it's possible you might not want to leak it's value to clients.

You will need to set this config value to ensure the encrypted cursor data is secure. If not set a random value is used which will change with each deployment breaking older cursor values that clients might be using so best to set it.

# Secret key for general encryption operations like
# encrypting the cursor data
secret_key: supercalifajalistics

Paginating forward through your results

{
  "variables": {
    "cursor": "MJoTLbQF4l0GuoDsYmCrpjPeaaIlNpfm4uFU4PQ="
  }
}

query {
  products(first: 10, after: $cursor) {
    slug
    name
  }
}

Paginating backward through your results

query {
  products(last: 10, before: $cursor) {
    slug
    name
  }
}

"data": {
   "products": [
    {
      "slug": "eius-nulla-et-8",
      "name" "Pale Ale"
    },
    {
      "slug": "sapiente-ut-alias-12",
      "name" "Brown Ale"
    }
    ...
  ],
  "products_cursor": "dJwHassm5+d82rGydH2xQnwNxJ1dcj4/cxkh5Cer"
}

Nested tables can also have cursors. Requesting multiple cursors are supported on a single request but when paginating using a cursor only one table is currently supported. To explain this better, you can only use a before or after argument with a cursor value to paginate a single table in a query.

query {
  products(last: 10) {
    slug
    name
    customers(last: 5) {
      email
      full_name
    }
  }
}

Multiple order-by arguments are supported. Super Graph is smart enough to allow cursor based pagination when you also need complex sort order like below.

query {
  products(
    last: 10
    before: $cursor
    order_by: [ price: desc, total_customers: asc ]) {
    slug
    name
  }
}

Using Variables

Variables ($product_id) and their values ("product_id": 5) can be passed along side the GraphQL query. Using variables makes for better client side code as well as improved server side SQL query caching. The built-in web-ui also supports setting variables. Not having to manipulate your GraphQL query string to insert values into it makes for cleaner and better client side code.

// Define the request object keeping the query and the variables seperate
var req = {
  query: "{ product(id: $product_id) { name } }",
  variables: { product_id: 5 },
};

// Use the fetch api to make the query
fetch("http://localhost:8080/api/v1/graphql", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify(req),
})
  .then((res) => res.json())
  .then((res) => console.log(res.data));