ClickHouse.md

https://clickhouse.com/ Column oriented DBMS for OLAP + Real-Time analytics created originally by Yandex (now open sourced under Apache 2.0, also as a Cloud service)

• designed to handle large volumes of data at high speed.
• uses columnar storage and data compression techniques to optimize query performance
• distributed architecture that allows it to scale horizontally, making it well-suited for big data applications.
• Runs on bare metal to cloud / Shared nothing architecture
• Parallel and vectorized execution

Main product parts:

• System
• Installation
• Maintenance

Extra parts

• Altinity: Deployments Manager
• SQL Dialect
• Clients

![[ClickHouse overview.png]]

Working with Time Series Data in ClickHouse

Uber replaced Elasticsearch with ClickHouse for logging, a good primary key could be a compound key like PRIMARY KEY(log_level, ..., timestamp)

Companies using ClickHouse for logs:

• Cloudflare: https://blog.cloudflare.com/log-analytics-using-clickhouse/
• Uber: https://www.uber.com/blog/logging/
• Ebay: https://tech.ebayinc.com/engineering/ou-online-analytical-processing