Velr (Rust driver)

Velr is an embedded property-graph database written in Rust from Velr.ai.

This crate provides the Rust driver for Velr. It links against a bundled native runtime (C ABI) shipped under prebuilt/.

Questions, feedback, or commercial licensing: tomas@velr.ai

Installation

Add to Cargo.toml:

[dependencies]
velr = "0.1"

Enable Arrow IPC support (binding Arrow arrays + exporting result tables as Arrow IPC):

[dependencies]
velr = { version = "0.1", features = ["arrow-ipc"] }

Quick start

use velr::{Velr, CellRef};

fn main() -> velr::Result<()> {
    // Open in-memory DB (pass Some("path.db") for file-backed)
    let db = Velr::open(None)?;

    db.run("CREATE (:Person {name:'Keanu Reeves', born:1964})")?;

    let mut t = db.exec_one("MATCH (p:Person) RETURN p.name AS name, p.born AS born")?;

    println!("{:?}", t.column_names());

    t.for_each_row(|row| {
        match row[0] {
            CellRef::Text(bytes) => println!("name={}", std::str::from_utf8(bytes).unwrap()),
            _ => {}
        }
        match row[1] {
            CellRef::Integer(i) => println!("born={i}"),
            _ => {}
        }
        Ok(())
    })?;

    Ok(())
}

Streaming multiple result tables

A single exec() can yield multiple result tables (e.g. multiple statements):

let db = Velr::open(None)?;
let mut stream = db.exec(
    "MATCH (m:Movie {title:'The Matrix'}) RETURN m.title AS title;
     MATCH (m:Movie {title:'Inception'})  RETURN m.released AS year"
)?;

while let Some(mut table) = stream.next_table()? {
    println!("{:?}", table.column_names());
    table.for_each_row(|row| {
        println!("{row:?}");
        Ok(())
    })?;
}

Transactions and savepoints

let db = Velr::open(None)?;

let tx = db.begin_tx()?;
tx.run("CREATE (:Temp {k:'t1'})")?;

{
    let sp = tx.savepoint_named("sp1")?;
    tx.run("CREATE (:Temp {k:'inner'})")?;
    sp.rollback()?; // rollback to savepoint, then release it
}

tx.commit()?;

Dropping an active transaction without commit() will roll it back (RAII).

Arrow IPC (optional)

With features = ["arrow-ipc"] you can:

• Bind Arrow arrays as a logical table (bind_arrow, bind_arrow_chunks)
• Export a result table as an Arrow IPC file (to_arrow_ipc_file())

#[cfg(feature = "arrow-ipc")]
fn arrow_example() -> velr::Result<()> {
    use arrow2::array::{Array, Utf8Array};

    let db = Velr::open(None)?;

    let cols = vec!["name".to_string()];
    let arrays: Vec<Box<dyn Array>> = vec![
        Utf8Array::<i64>::from(vec![Some("Alice"), Some("Bob")]).boxed(),
    ];

    db.bind_arrow("_people", cols, arrays)?;
    db.run("UNWIND BIND('_people') AS r CREATE (:Person {name:r.name})")?;

    let mut t = db.exec_one("MATCH (p:Person) RETURN p.name AS name ORDER BY name")?;
    let ipc = t.to_arrow_ipc_file()?;

    println!("IPC bytes: {}", ipc.len());
    Ok(())
}

Platform support

This crate links against a bundled native runtime shipped under prebuilt/.

Currently bundled targets:

• macOS universal (arm64 + x86_64)
• Linux x86_64
• Linux aarch64
• Windows x86_64

License

This project is licensed under the Velr Beta Test License v1.0.

• Evaluation / beta use only
• No production use
• No redistribution

See LICENSE for the full terms.