# Integrating with ClickHouse

### Overview

This guide describes how to connect a **ClickHouse data source** to **Drivetrain**. Drivetrain supports two integration methods:

1. **Method 1: Sharing a ClickHouse View *****(Recommended)***\
   Provides a curated, aggregated interface for efficient, low-volume data extraction.
2. **Method 2: Direct Database Access**\
   Provides direct querying of tables or custom SQL, with safeguards to control data volume.

Both methods require that the credentials provided have the appropriate permissions to read the specified objects.

### Method 1: Sharing a ClickHouse View *(Recommended)*

Sharing a **ClickHouse view** allows you to expose only the necessary business logic and pre-aggregated data to Drivetrain. This improves performance and reduces data transfer.

#### Required details

Provide the following information:

* **Hostname**
* **Port**
* **Username**\
  (A ClickHouse user with read access to the view)
* **Password**
* **View name**\
  (fully qualified, e.g., <mark style="color:green;">`<database>.<view_name>`</mark>)

#### Permissions

Ensure that the user has:

* **SELECT** privileges on the specified view
* Access to any underlying objects the view depends on

#### Best practices

* Use a **read-only user** scoped to only the required view
* Expose only the fields needed by Drivetrain
* Pre-aggregate data where possible to **limit data volume**

### Method 2: Direct Database Access

This method connects directly to the ClickHouse database and pulls data using a specified query. Drivetrain will use the host/port/credentials to run the query.

#### Required details

Provide the following:

* **Hostname**
* **Port**
* **Username**
* **Password**
* **Database name**
* **Table name** (the target table to extract from)
* **Query to pull the data**\
  (A **SELECT** query that returns only the necessary results)

#### Query Requirements

* Return only necessary columns
* Consider date filters or limits to prevent large data scans
* Avoid <mark style="color:green;">`SELECT *`</mark> on large tables

#### Permissions

Ensure the user has:

* **SELECT** privileges on the target table(s)
* Appropriate access to any referenced schemas

#### Best practices

* Always include filters (e.g., date ranges) to **control volume**
* Use views layer if the query is complex or resource-intensive
* Validate performance and indexing before enabling production sync


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