Get Started with Hasura DDN and ClickHouse
Overview
This tutorial takes about fifteen minutes to complete. You'll learn how to:
- Set up a new Hasura DDN project
- Connect it to a ClickHouse instance
- Generate Hasura metadata
- Create a build
- Run your first query
Additionally, we'll familiarize you with the steps and workflows necessary to iterate on your API.
This tutorial assumes you're starting from scratch. We'll use a locally running ClickHouse instance via Docker and connect it to Hasura, but you can easily follow the steps if you already have data seeded or are using ClickHouse's hosted service; Hasura will never modify your source schema.
Prerequisites
Install the DDN CLI
- macOS and Linux
- Windows
Simply run the installer script in your terminal:
curl -L https://graphql-engine-cdn.hasura.io/ddn/cli/v4/get.sh | bash
- Download the latest DDN CLI installer for Windows.
- Run the
DDN_CLI_Setup.exe
installer file and follow the instructions. This will only take a minute. - By default, the DDN CLI is installed under
C:\Users\{Username}\AppData\Local\Programs\DDN_CLI
- The DDN CLI is added to your
%PATH%
environment variable so that you can use theddn
command from your terminal.
Install Docker
The Docker based workflow helps you iterate and develop locally without deploying any changes to Hasura DDN, making the
development experience faster and your feedback loops shorter. You'll need Docker Compose v2.27.1
or later.
Validate the installation
You can verify that the DDN CLI is installed correctly by running:
ddn doctor
Tutorial
Step 1. Authenticate your CLI
ddn auth login
This will launch a browser window prompting you to log in or sign up for Hasura DDN. After you log in, the CLI will acknowledge your login, giving you access to Hasura Cloud resources.
Step 2. Scaffold out a new local project
ddn supergraph init my-project && cd my-project
Once you move into this directory, you'll see your project scaffolded out for you. You can view the structure by either
running ls
in your terminal, or by opening the directory in your preferred editor.
Step 3. Initialize your ClickHouse connector
ddn connector init my_ch -i
From the dropdown, start typing clickhouse
and hit enter to accept the default port. Then, provide the following
values:
Connection string
http://local.hasura.dev:8123
Username
default_user
Password
default_password
Step 4. Start the local ClickHouse container
touch app/connector/my_ch/compose.clickhouse.yaml
services:
clickhouse:
image: clickhouse/clickhouse-server
container_name: clickhouse-server
ports:
- "8123:8123"
- "9000:9000"
volumes:
- ./clickhouse-data:/var/lib/clickhouse
environment:
CLICKHOUSE_USER: "default_user"
CLICKHOUSE_PASSWORD: "default_password"
CLICKHOUSE_DB: "default"
docker compose -f app/connector/my_ch/compose.clickhouse.yaml up -d
curl -u default_user:default_password -X POST \
--data "CREATE TABLE users (user_id UInt32, name String, age UInt8) ENGINE = MergeTree() ORDER BY user_id;" \
http://localhost:8123
curl -u default_user:default_password -X POST \
--data "INSERT INTO users (user_id, name, age) VALUES (1, 'Alice', 25), (2, 'Bob', 30), (3, 'Charlie', 35);" \
http://localhost:8123
curl -u default_user:default_password -X POST \
--data "SELECT * FROM users;" \
http://localhost:8123
You should see a list of users returned.
Step 5. Introspect your ClickHouse database
ddn connector introspect my_ch
After running this, you should see a representation of your database's schema in the
app/connector/my_ch/configuration.json
file; you can view this using cat
or open the file in your editor.
ddn connector show-resources my_ch
Step 6. Add your model
ddn models add my_ch users
Open the app/metadata
directory and you'll find a newly-generated file: Users.hml
. The DDN CLI will use this Hasura
Metadata Language file to represent the users
table from ClickHouse in your API as a
model.
Step 7. Create a new build
ddn supergraph build local
The build is stored as a set of JSON files in engine/build
.
Step 8. Start your local services
ddn run docker-start
Your terminal will be taken over by logs for the different services.
Step 9. Run your first query
ddn console --local
query {
users {
userId
name
age
}
}
{
"data": {
"users": [
{
"userId": 1,
"name": "Alice",
"age": 25
},
{
"userId": 2,
"name": "Bob",
"age": 30
},
{
"userId": 3,
"name": "Charlie",
"age": 35
}
]
}
}
Step 10. Iterate on your ClickHouse schema
curl -u default_user:default_password -X POST \
--data "CREATE TABLE posts (
user_id UInt32,
post_id UInt32,
title String,
content String
) ENGINE = MergeTree()
ORDER BY user_id;" \
http://localhost:8123
curl -u default_user:default_password -X POST \
--data "INSERT INTO posts (user_id, post_id, title, content) VALUES
(1, 1, 'My First Post', 'This is Alice''s first post.'),
(1, 2, 'Another Post', 'Alice writes again!'),
(2, 3, 'Bob''s Post', 'Bob shares his thoughts.'),
(3, 4, 'Hello World', 'Charlie joins the conversation.');" \
http://localhost:8123
curl -u default_user:default_password -X POST \
--data "SELECT * FROM posts;" \
http://localhost:8123
Step 11. Refresh your metadata and rebuild your project
The following steps are necessary each time you make changes to your source schema. This includes, adding, modifying, or dropping tables.
Step 11.1. Re-introspect your data source
ddn connector introspect my_ch
In app/connector/my_ch/configuration.json
, you'll see schema updated to include operations for the posts
table. In
app/metadata/my_ch.hml
, you'll see posts
present in the metadata as well.
Step 11.2. Update your metadata
ddn model add my_ch posts
Step 11.3. Kill your services
Bring down the services by pressing CTRL+C
in the terminal tab logging their activity.
Step 11.4. Create a new build
ddn supergraph build local
Step 11.5 Restart your services
ddn run docker-start
Step 12. Query your new build
query GetPosts {
posts {
userId
postId
title
content
}
}
{
"data": {
"posts": [
{
"userId": 1,
"postId": 1,
"title": "My First Post",
"content": "This is Alice's first post."
},
{
"userId": 1,
"postId": 2,
"title": "Another Post",
"content": "Alice writes again!"
},
{
"userId": 2,
"postId": 3,
"title": "Bob's Post",
"content": "Bob shares his thoughts."
},
{
"userId": 3,
"postId": 4,
"title": "Hello World",
"content": "Charlie joins the conversation."
}
]
}
}
Step 13. Create a relationship
---
kind: Relationship
version: v1
definition:
name: user
sourceType: Posts
target:
model:
name: Users
relationshipType: Object
mapping:
- source:
fieldPath:
- fieldName: userId
target:
modelField:
- fieldName: userId
We've created an extension for VS Code that leverages LSP to make authoring these metadata objects easier. Check it out here.
Step 14. Rebuild your project
Bring down the services by pressing CTRL+C
in the terminal tab logging their activity.
ddn supergraph build local
ddn run docker-start
Step 15. Query using your relationship
query GetPosts {
posts {
postId
title
content
user {
userId
name
age
}
}
}
{
"data": {
"posts": [
{
"postId": 1,
"title": "My First Post",
"content": "This is Alice's first post.",
"user": {
"userId": 1,
"name": "Alice",
"age": 25
}
},
{
"postId": 2,
"title": "Another Post",
"content": "Alice writes again!",
"user": {
"userId": 1,
"name": "Alice",
"age": 25
}
},
{
"postId": 3,
"title": "Bob's Post",
"content": "Bob shares his thoughts.",
"user": {
"userId": 2,
"name": "Bob",
"age": 30
}
},
{
"postId": 4,
"title": "Hello World",
"content": "Charlie joins the conversation.",
"user": {
"userId": 3,
"name": "Charlie",
"age": 35
}
}
]
}
}
Next steps
Congratulations on completing your first Hasura DDN project with ClickHouse! 🎉
Here's what you just accomplished:
- You started with a fresh project and connected it to a local ClickHouse database.
- You set up metadata to represent your tables and relationships, which acts as the blueprint for your API.
- Then, you created a build — essentially compiling everything into a ready-to-use API — and successfully ran your first GraphQL queries to fetch data.
- Along the way, you learned how to iterate on your schema and refresh your metadata to reflect changes.
Now, you're equipped to connect and expose your data, empowering you to iterate and scale with confidence. Great work!
Take a look at our ClickHouse docs to learn more about how to use Hasura DDN with ClickHouse. Or, if you're ready, get started with adding permissions to control access to your API.