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ClickHouse

Connect to ClickHouse using the HTTP interface authenticated with HTTP basic credentials. The same connector works with ClickHouse Cloud and self-hosted clusters.

Prerequisites

Section titled “Prerequisites”

Before creating a connection, you need:

  1. A ClickHouse server reachable from the public internet, or a ClickHouse Cloud service
  2. A user with read-only privileges on the database you want to query
  3. The HTTP(S) endpoint URL for the server. ClickHouse Cloud exposes this on the service overview page; self-hosted clusters typically expose it on port 8443 (HTTPS) or 8123 (HTTP)

Creating a read-only user

Section titled “Creating a read-only user”

For least-privilege access, we recommend creating a dedicated user for Reeflow rather than reusing an admin account. ClickHouse’s access control documentation covers this in more depth.

ClickHouse Cloud

Section titled “ClickHouse Cloud”

Open the SQL console from the left sidebar in your ClickHouse Cloud service and run the following. ClickHouse Cloud passwords must be at least 12 characters and include uppercase letters, lowercase letters, and numbers or special characters.

-- Create a dedicated user
CREATE USER IF NOT EXISTS reeflow_reader
IDENTIFIED WITH sha256_password BY 'Change_me_123!';

-- Read access on the target database
GRANT SHOW TABLES, SELECT ON default.* TO reeflow_reader;

-- Allow the user to introspect schemas via the system tables Reeflow uses
GRANT SELECT ON system.tables TO reeflow_reader;
GRANT SELECT ON system.columns TO reeflow_reader;
GRANT SELECT ON system.databases TO reeflow_reader;

Self-hosted

Section titled “Self-hosted”

Run the following as a user with CREATE USER and GRANT privileges (typically default on a fresh cluster), customising the user name and database to match your environment:

-- Create a dedicated user
CREATE USER IF NOT EXISTS reeflow_reader
IDENTIFIED WITH sha256_password BY 'change_me';

-- Read access on the target database
GRANT SHOW TABLES, SELECT ON default.* TO reeflow_reader;

-- Allow the user to introspect schemas via the system tables Reeflow uses
GRANT SELECT ON system.tables TO reeflow_reader;
GRANT SELECT ON system.columns TO reeflow_reader;
GRANT SELECT ON system.databases TO reeflow_reader;

Configuration

Section titled “Configuration”

When creating a ClickHouse connection in Reeflow, provide the following:

FieldDescription
URLHTTP(S) endpoint of the ClickHouse server. On ClickHouse Cloud, find it by selecting your service and clicking Connect → HTTPS — the hostname appears in the example curl command (e.g. https://abc123.eu-central-1.aws.clickhouse.cloud:8443). For a self-hosted cluster, this is typically port 8443 (HTTPS) or 8123 (HTTP).
UsernameThe ClickHouse user that owns the credentials
PasswordThe user’s password
DatabaseDefault database queries are issued against

Creating a connection

Section titled “Creating a connection”

Create a ClickHouse connection

Add a ClickHouse server as a data source in Reeflow.

Navigate to Connections in the main navigation, then click New Connection.

Enter a Name for the connection and an optional Description.

Select ClickHouse as the connection type.

Enter the URL, Username, Password, and Database.

Click Test Connection to verify your credentials are correct.

Click Create Connection to save. The connection appears in your connections list.
Section titled “Related”