Safer SQL in Rust: Why We Use Diesel with PostgreSQL

When building backend systems in Rust, choosing the right way to interface with your database is a big decision. Diesel and SQLx are the two most prominent options for compile-time SQL safety, each offering their own advantages. At Bosque, we’ve standardized on Diesel, particularly alongside PostgreSQL, and our experience has been positive across the board.

Compile-Time Safety: The Core Advantage

Both Diesel and SQLx aim to prevent runtime SQL errors by verifying queries at compile time. Diesel achieves this through Rust's type system, embedding SQL semantics directly into the type checker. SQLx, on the other hand, connects to a live database during compilation to validate SQL queries and ensure they’re compatible with the actual schema.

While we haven’t used SQLx in production, we’ve reviewed its approach and appreciate the philosophy behind it. For our needs, Diesel’s model made more sense, especially in projects where we want guarantees without needing a live database during development or CI.

Working with Diesel and PostgreSQL

Diesel’s query DSL takes some getting used to if you’re coming from traditional SQL, but once familiar, it provides excellent feedback at compile time. For example:

users.filter(name.eq("John")).select(email)

Compared to raw SQL, it’s more verbose, but the benefit is that you get strong guarantees that your queries are valid and your schema aligns with your Rust types. This has helped us catch bugs early, especially as the database evolves.

PostgreSQL has been a great companion to Diesel. The type support is strong, and we’ve been able to leverage Postgres features like enums and JSONB with minimal friction. Diesel's documentation has also been a major asset — it’s clear, thorough, and has helped our team ramp up quickly.

Schema and Migrations

Diesel includes a CLI tool that not only manages migrations but also generates Rust code from the schema. This has helped us keep the database and application logic tightly in sync. It’s straightforward to version and review schema changes, and the generated code gives us an additional layer of type safety.

Looking Ahead

We remain open to exploring SQLx, particularly for situations where raw SQL might be preferable. That said, Diesel’s approach has served us well so far. The safety, Postgres integration, and well-maintained tooling have made it a natural fit for our Rust backend stack.

If you're starting a new Rust project and type safety is high on your priority list, Diesel is well worth considering.