---
title: "Ten years of ClickHouse in open source"
description: "ClickHouse’s tenth-anniversary history describes its path from an internal web-analytics experiment to an open-source analytical database with more than 2,000 contributors. The original problem was processing rapidly growing, real-time logs while answering flexible reports quickly; tested MySQL extensions and standalone analytical databases did not meet the stated scale of 100 billion records per day and 500 columns. The project built column-oriented storage, lightweight compression, custom aggregation structures, background merges, and query support for grouping, aggregation, filtering, and sorting. Released publicly on June 15, 2016, ClickHouse is presented as a level-three open-source project with public contribution guidelines, code review, testing, CI, documentation, and a roadmap, while contributors receive credit even when implementations are substantially rewritten."
---

# Ten years of ClickHouse in open source

[Clickhouse](https://yomu.fyi/company/clickhouse) · Jun 15, 2026

**Type:** Explainer

## Summary

ClickHouse’s tenth-anniversary history describes its path from an internal web-analytics experiment to an open-source analytical database with more than 2,000 contributors. The original problem was processing rapidly growing, real-time logs while answering flexible reports quickly; tested MySQL extensions and standalone analytical databases did not meet the stated scale of 100 billion records per day and 500 columns. The project built column-oriented storage, lightweight compression, custom aggregation structures, background merges, and query support for grouping, aggregation, filtering, and sorting. Released publicly on June 15, 2016, ClickHouse is presented as a level-three open-source project with public contribution guidelines, code review, testing, CI, documentation, and a roadmap, while contributors receive credit even when implementations are substantially rewritten.

## Context

The work began in a web-analytics system where data volumes were growing, new logs arrived in real time, and processing delays accumulated unless five-minute chunks could be handled within five minutes. Existing MySQL-based storage, custom data structures, and tested analytical databases did not reasonably support the required scale and flexible reporting.

## Approach / What changed

The project developed column-oriented storage for structured logs, lightweight compression, queryable grouping and aggregation, custom C++ data structures for incremental aggregation, background merges, and support for real-time analytical queries. Its open-source model aims for transparent development with contribution guidelines, tracking, code review, testing, CI, releases, support, and documentation.

## Takeaways

- The initial OLAPServer prototype stored each integer column in daily, website-specific binary files and exposed grouping, aggregation, filtering, and sorting through an API.
- ClickHouse used custom C++ aggregation structures with add, update, merge, serialization, and deserialization methods, allowing partially aggregated data to be merged on reads.
- The project defines level-three open source as including open contribution guidelines, a task tracker, code review, a roadmap, testing and CI, a release cycle, user support, and documentation.

**Tags:** [MySQL](https://yomu.fyi/topic/mysql), [Open Source](https://yomu.fyi/topic/open-source), [Performance](https://yomu.fyi/topic/performance), [Postgres](https://yomu.fyi/topic/postgres), [Scalability](https://yomu.fyi/topic/scalability)

- Source: [Clickhouse](https://clickhouse.com/blog/open-source-10)
- Source URL: https://clickhouse.com/blog/open-source-10
- Ingested by Yomu: 2026-08-29T01:35:14.550Z

[Read original post](https://clickhouse.com/blog/open-source-10)