ClickHouse C – Header-Only Client for Native Binary Protocol

Why Bypass SQL for Native Protocol Access?

A new header-only C library enables direct communication with ClickHouse using its native binary protocol over TCP, allowing applications to exchange data in the system's internal format without relying on HTTP or SQL interfaces. The library, named clickhouse-c, provides a lightweight interface for sending and receiving native format blocks, designed for integration into performance-sensitive environments such as database extensions.

The client consists of a single core header file with optional follow-up headers for TCP handling, compression, codec support, and I/O backends. It is specifically engineered to work within PostgreSQL extensions, utilizing palloc for memory allocation and supporting longjmp for error handling, while avoiding any PostgreSQL-specific dependencies. By including only clickhouse.h, developers gain access to a minimal yet functional client that speaks ClickHouse’s wire protocol directly.

How Does It Handle Memory and Errors in Extensions?

Using the native binary protocol reduces overhead compared to traditional SQL-over-HTTP approaches, particularly beneficial in scenarios requiring high-throughput data ingestion or low-latency querying. The protocol transmits data in ClickHouse’s internal columnar format, eliminating parsing and serialization costs associated with text-based interfaces. This makes the client ideal for embedding in systems where performance and resource efficiency are critical, such as custom storage engines or real-time analytics plugins.

The library integrates safely with PostgreSQL’s memory management context by using palloc for allocations, ensuring memory is freed appropriately within the extension’s lifecycle. Error handling leverages setjmp/longjmp mechanisms, allowing the client to recover from network or protocol failures without crashing the host process. These design choices make it suitable for use in trusted extension environments where stability and predictability are paramount.

What advantages does the native protocol offer over HTTP-based clients? The native protocol avoids HTTP parsing, JSON/XML serialization, and SQL parsing overhead, enabling faster data transfer and lower CPU usage, especially for bulk operations.

Frequently Asked Questions

Is the client compatible with all ClickHouse server versions? It is designed to work with recent versions of ClickHouse that support the native TCP protocol; compatibility depends on matching protocol versions between client and server.

Can this be used outside of PostgreSQL extensions? Yes, while optimized for PostgreSQL extension use, the library is generic and can be embedded in any C or C++ application requiring direct ClickHouse access.