A Year of Rust in ClickHouse

Alexey Milovidov
14 min readbeginner
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Overview

The article discusses the integration of Rust into ClickHouse, emphasizing the strategic decision to enhance the system without rewriting it entirely in Rust. It details the initial steps taken, the challenges faced during integration, and the benefits observed from utilizing Rust libraries.

What You'll Learn

1

How to integrate Rust components into a C++ codebase

2

Why using Rust can improve performance in specific applications

3

When to choose Rust libraries over existing C++ implementations

Prerequisites & Requirements

  • Understanding of C++ and Rust programming languages
  • Experience with building and integrating libraries in C++(optional)

Key Questions Answered

What was the first Rust component integrated into ClickHouse?
The first Rust component integrated into ClickHouse was the BLAKE3 hash function, which was implemented in Rust and tested for integration into the build system. This decision was made to allow the use of Rust without rewriting the entire codebase.
What challenges were faced during the integration of Rust into ClickHouse?
Challenges included ensuring a hermetic build process, managing memory safety between Rust and C++, and handling Rust's lack of exceptions. These issues required careful management of dependencies and rigorous testing to prevent crashes.
How does PRQL differ from SQL in ClickHouse?
PRQL is a query language that allows expressing queries in a pipelined, composable form, which is more syntax-heavy than SQL. It provides an alternative way to write queries but lacks some interactive features available in SQL.

Technologies & Tools

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Key Actionable Insights

1
Consider integrating Rust for performance-critical components in C++ applications.
Rust's memory safety and performance can enhance specific functionalities without a complete rewrite of existing systems.
2
Utilize CI systems to catch integration issues between Rust and C++ early in the development process.
Implementing fuzzing and sanitizers can help identify memory management issues and crashes before merging code.
3
Evaluate the trade-offs of using Rust libraries versus existing C++ implementations.
While Rust can offer performance benefits, it may introduce complexity in integration and dependency management.

Common Pitfalls

1
Failing to manage memory ownership between Rust and C++ can lead to segmentation faults.
This occurs because Rust's memory safety features require careful handling of memory allocation and deallocation when interfacing with C++.
2
Assuming Rust's safety guarantees eliminate the need for traditional debugging tools.
Even with Rust's safety features, integrating it into a C++ codebase necessitates the continued use of sanitizers and other debugging tools to ensure overall application stability.

Related Concepts

Memory Safety In Programming Languages
Integration Of Multiple Programming Languages
Performance Optimization Techniques