June 24, 2026
Build speed? More like rebuild drama
Optimizing [sqlx:test] rebuild time
One tiny test trick made rebuilds crawl, and the comments instantly turned nostalgic
TLDR: A developer found that a convenient testing feature was bloating every test run by repeatedly embedding database setup data, slowing small rebuilds to a crawl. The comment section’s defining mood was weary amusement, with readers reacting like veterans watching yet another “helpful” tool turn into a time thief.
A Rust developer went digging into why their project’s tests felt painfully slow to rebuild, and the big reveal was surprisingly petty: a handy test helper was quietly stuffing huge chunks of database setup text into every single test behind the scenes. Translation for normal people: every time they made a small edit, their computer was re-packing the same giant suitcase over and over again, and that was eating seconds off their day. In fast-feedback coding land, that’s enough to spark real annoyance.
The community reaction, though, was the real mood setter. Instead of a giant flame war, the comments arrived with that classic internet blend of war flashbacks, gallows humor, and instant aging. The standout line came from dented42: “Gods I feel old…” — which pretty much captured the emotional energy of the thread. It’s the kind of reaction that says, “We used to complain about one problem, and now the problem has evolved into a deluxe, extra-complicated version of itself.”
There’s also a quiet drama underneath the post: developers love tools that save time, right up until those same tools secretly make every rebuild drag. That tension is the hot take here. The article itself is a detective story about hidden slowdown, but the comments turn it into something even juicier: a shared community sigh that modern software tools are amazing, cursed, and somehow both at once.
Key Points
- •The article profiles slow incremental rebuilds in a Rust project with many `#[sqlx::test]` integration tests, where recompiling tests after small changes took roughly 7.5 to 10 seconds.
- •Several factors were identified in the slow rebuilds: debug information generation, `rustc` incremental session overhead, and linker time, with `lld` taking about one second versus about 200 ms for `wild`.
- •The build was performed with `SQLX_OFFLINE=1`, so the slowdown was not caused by live database connections during compilation.
- •Each `#[sqlx::test]` macro invocation reads migrations from disk, parses, validates, and hashes them, but the article says this processing was not the main bottleneck.
- •The main `sqlx`-related compile-time cost came from macro expansion that embeds a full migration list, including SQL text and checksum byte arrays, into generated Rust source for every test.