v.25.10Improvement

Setting enable_http_compression is now the default

The setting enable_http_compression is now the default. This means that if a client accepts HTTP compression, the server will use it. However, this change has certain downsides. The client can request a heavy compression method, such as bzip2, which is unreasonable, and it will increase the resource consumption of the server (but this will be visible only when large results are transferred). The client can request gzip, which is not that bad, but suboptimal compared to zstd. Closes #71591. #87703 (Alexey Milovidov).
The setting enable_http_compression is now enabled by default, allowing ClickHouse to automatically use HTTP compression when the client supports it.

Why it matters

This feature aims to improve network efficiency and reduce data transfer sizes by enabling HTTP compression by default. It solves the problem of uncompressed large result transfers, thereby saving bandwidth and potentially improving query response times. However, clients can request different compression methods, including heavy ones like bzip2, which may increase server resource usage.

How to use it

To use this feature, no action is needed since enable_http_compression is enabled by default. Clients should include the appropriate Accept-Encoding HTTP header to specify their supported compression methods. The server will honor this and compress responses accordingly.