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We’re going to create a simple social network where users can follow each other and create posts.

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Prerequisites

Install the HelixDB CLI 
curl -sSL https://helix.sh/install.sh | bash
Install the Helix container 
helix install
Initialize a new project 
helix init
Install the SDK of your choice (optional) 
pip install helix-py
Setup the SDK of your choice (optional) 
from helix.client import Client
client = Client(local=True)

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Step 1: Define the schema in schema.hx

We’re going to define the schema for our social network in schema.hx. We’re going to have User nodes where users can Follow other users. We’re also going to have Post nodes where users can Create posts.
schema.hx
N::User {
    name: String,
    age: U32,
    email: String,
    created_at: Date DEFAULT NOW,
    updated_at: Date DEFAULT NOW,
}

N::Post {
    content: String,
    created_at: Date DEFAULT NOW,
    updated_at: Date DEFAULT NOW,
}

E::Follows {
    From: User,
    To: User,
    Properties: {
        since: Date DEFAULT NOW,
    }
}

E::Created {
    From: User,
    To: Post,
    Properties: {
        created_at: Date DEFAULT NOW,
    }
}

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Step 2: Inserting data

Creating a user is done by inserting a new node into the graph. 
QUERY createUser(name: String, age: U32, email: String) =>
    user <- AddN<User>({name: name, age: age, email: email})
    RETURN user
To let users follow another user, we need to create an edge between them. 
QUERY createFollow(follower_id: ID, followed_id: ID) =>
    follower <- N<User>(follower_id)
    followed <- N<User>(followed_id)
    AddE<Follows>::From(follower)::To(followed) // don't need to specify the `since` property because it has a default value
    RETURN "success"
To create a post, we need to create a post node and an edge between the user and the post. 
QUERY createPost(user_id: ID, content: String) =>
    user <- N<User>(user_id)
    post <- AddN<Post>({content: content})
    AddE<Created>::From(user)::To(post) // don't need to specify the `created_at` property because it has a default value
    RETURN post

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Step 3: Query the data

To get all users, we can use the following query: 
QUERY getUsers() =>
    users <- N<User>
    RETURN users
To get all posts, we can use the following query: 
QUERY getPosts() =>
    posts <- N<Post>
    RETURN posts
To get all posts by a user, we can use the following query: 
QUERY getPostsByUser(user_id: ID) =>
    posts <- N<User>(user_id)::Out<Created>
    RETURN posts
To get all users that a user follows, we can use the following query: 
QUERY getFollowedUsers(user_id: ID) =>
    followed <- N<User>(user_id)::Out<Follows>
    RETURN followed
As a more complex example, we could have a query that loads an page containing the posts of users that a user follows. To do this we are going to remap the posts to have a field containing information about the user that created the post. 
QUERY getFollowedUsersPosts(user_id: ID) =>
    followers <- N<User>(user_id)::Out<Follows>
    posts <- followers::Out<Created>::RANGE(0, 40)
    RETURN posts::{
        post: _::{content},
        creatorID: _::In<Created>::ID,
    }

"posts": [
    {
        "post": "Hello, world!",
        "creatorID": "123"
    },
    {
        "post": "Hello, world!",
        "creatorID": "123"
    },
    ... // up to 40 posts
]

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Step 4: Run the queries

To run the queries, we can use the following command 
helix push <instance_name>
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