Optimizing #[sqlx::test] rebuild time

This article discusses the problem of slow incremental rebuild times (~8-10s) for Rust tests using the #[sqlx::test] attribute, specifically in the bors merge queue bot project. The author profiles the build time and identifies several factors: debug info generation, incremental session loading, linker speed, and sqlx test compilation. The focus is on sqlx test compilation, which remains slow even with SQLX_OFFLINE=1 and opt-level=3 for sqlx-macros. The author explains how #[sqlx::test] works, including database creation, migration loading from disk, and parsing, and begins to analyze why compilation is slow despite offline mode.