Rust library

Crate relativedb (edition 2021); depends only on chrono and libloading.

cd rust
cargo test

API shape

use relativedb::{Engine, ExecutionInput, RetrieverWiring, Schema, /* ... */};

let schema = Schema::new_schema()... .build();
let wiring = RetrieverWiring::new_wiring()
    .entities("customers", /* closure */)
    .default_links(/* closure: newest-first, honors bound + limit */)
    .scanner("customers", /* closure: enables FOR EACH + CSC */)
    .build();

let mut engine = Engine::new(schema, wiring);
let result = engine.execute(
    ExecutionInput::query("PREDICT ...").anchor_time(t0))?;

Modules: schema, retrieve, pql (hand-written recursive-descent parser, no ANTLR runtime), engine, model, native, csc. Errors surface through relativedb::Result / relativedb::Error.

Design decision: synchronous SPI

Where Java's SPI is async, the Rust (and Python) SPI is synchronous and infallible — traits return plain Vecs. An async SPI would force a runtime choice on every user and color the whole engine async; batching retrievers can run their own I/O concurrency internally.

Native backend

native::RtNativeBackend binds librt_c via libloading, discovered from RELATIVEDB_RT_LIB or the sibling cpp/build/. The golden gate:

RELATIVEDB_RT_LIB=../cpp/build/librt_c.dylib \
  cargo test --test golden_tests -- --nocapture

The shared 44-query PQL corpus lives in this crate (tests/data/examples.pql) and is exercised by all three languages.