> ## Documentation Index
> Fetch the complete documentation index at: https://oxy.tech/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# ClickHouse

This guide explains how to connect to ClickHouse with Oxygen. ClickHouse is an open-source column-oriented DBMS for real-time analytics.

## Configuration Options

Add your ClickHouse configuration to `config.yml`. Here are all available parameters:

```yaml theme={null}
databases:
  - name: my_clickhouse_db # Unique identifier for this connection
    type: clickhouse
    host: "http://clickhouse.local:8123" # ClickHouse server url with protocol://hostname:port
    user: "default" # Username for authentication
    password: <password> # Direct password (not recommended)
    password_var: "CH_PWD" # Environment variable containing password (recommended)
    database: "default" # Database name to connect to
```

## Example Configurations

<Steps>
  <Step title="Prepare password environment variable">
    Export the environment variable:

    ```sh theme={null}
    export CH_PWD=<your password>
    ```

    Or put it in `.env` file:

    ```sh theme={null}
    echo CH_PWD=<your password> >> .env
    ```
  </Step>

  <Step title="Add ClickHouse configuration">
    ```yaml theme={null}
    databases:
      - name: local_ch
        type: clickhouse
        host: "http://clickhouse.local:8123"
        user: "default"
        password_var: "CH_PWD"
        database: "analytics"
    ```
  </Step>
</Steps>

## Troubleshooting

* Verify server status: `clickhouse-client --query "SELECT 1"`
* Check system logs: `/var/log/clickhouse-server/`
* Common ports: 8123 (HTTP), 9000 (TCP), 9009 (replication)
* Monitor server metrics: `system.metrics` table