diesel-cte-ext

A cheerful toolkit for building recursive and non-recursive Common Table Expressions (CTEs) on top of Diesel. The helpers wrap the boilerplate needed to assemble WITH blocks, keep column metadata tidy, and work with both blocking and async Diesel connections.

Highlights

• Friendly builders for WITH and WITH RECURSIVE queries via RecursiveCTEExt.
• Column helpers (columns! and table_columns!) that marry runtime names to compile-time Diesel metadata.
• Async-ready: enable the async feature to extend the helpers to diesel_async connections.
• Battle-tested Postgres integration tests powered by pg_embedded_setup_unpriv, so CI agents without root privileges can still run the suite end-to-end.

Quick start

Add the crate to your Cargo.toml:

[dependencies]
diesel-cte-ext = { version = "0.1", default-features = false, features = [
    "postgres",
] }

Build a recursive query:

use diesel::{dsl::sql, pg::PgConnection, sql_types::Integer, RunQueryDsl};
use diesel_cte_ext::{RecursiveCTEExt, RecursiveParts};

fn five_high(mut conn: PgConnection) -> diesel::QueryResult<Vec<i32>> {
    conn.with_recursive(
        "series",
        &["n"],
        RecursiveParts::new(
            sql::<Integer>("SELECT 1"),
            sql::<Integer>("SELECT n + 1 FROM series WHERE n < 5"),
            sql::<Integer>("SELECT n FROM series"),
        ),
    )
    .load(&mut conn)
}

Wrap Diesel expressions for the seed, step, or body fragments using the macro helpers when you need to inline SQL snippets:

use diesel::{dsl::sql, sql_types::Integer};
use diesel_cte_ext::{RecursiveCTEExt, RecursiveParts, cte_query, seed_query, step_query};

let parts = RecursiveParts::new(
    seed_query!(sql::<Integer>("SELECT 1")),
    step_query!(sql::<Integer>("SELECT n + 1 FROM series")),
    cte_query!(sql::<Integer>("SELECT n FROM series")),
);

See docs/users-guide.md for a fuller tour, including trait diagrams and advanced builder patterns.

Examples

Run the ready-to-go examples after enabling the relevant backend feature:

cargo run --example sqlite_fibonacci
cargo run --example sqlite_directory

Both examples use in-memory SQLite so they are quick to run repeatedly.

Testing

This repository ships a Makefile that drives formatting, linting, and tests with the strict flags configured in Cargo.toml:

make check-fmt
make lint
make test

make test spins up an embedded PostgreSQL instance via pg_embedded_setup_unpriv. The helper automatically provisions binaries, configures $PGPASSFILE, and shuts everything down between tests. No manual Postgres installation is required.

Have fun composing queries!