CQL NullableF64

This crate implements various CqlType derivatives for storing Option<f64> values in a CQL database.

Will allocate 9 bytes per value linked.

Benchmarks

Benchmarks supplied below are fairly rudimentary (and rounded) and are there to give a rough idea of relative costs. Full benchmark code can be found in github and can be run with rustup run nightly cargo bench.

Getting started

To get started, add the below dependencies to your Cargo.toml:

[dependencies]
//... (any existing dependencies you may have)
cql_db = "^0.2.4"
cql_nullable_f64 = "^0.2"

Then need to create a folder where you want the database to live, and then try out the below:

use std::io::{ Cursor, SeekFrom, Seek };
use std::error::Error;
use cql_nullable_f64::{ NullableF64, unpack_stream };

const DATABASE_LOCATION: &str = "PATH_TO_YOUR_DATABASE_DIRECTORY";

pub fn example_cql() -> Result<(), Error> {
    // create a one dimensional database to hold 3 points
    cql_db::create_db::<NullableF64>(
        DATABASE_LOCATION,
        &[3]
    )?;

    // write '-1.6', to [1]
    cql_db::write_value::<NullableF64>(
        DATABASE_LOCATION,
        &[1],
        Some(-1.6)
    )?;

    // write '5.4', to [3]
    cql_db::write_value::<NullableF64>(
        DATABASE_LOCATION,
        &[3],
        Some(5.4)
    )?;

    let mut result: [Option<f64>; 3] = [None; 3];
    let mut stream = Cursor::new(Vec::new());

    // read 3 values from [1] to 'stream'
    cql_db::read_to_stream::<NullableF64>(
        DATABASE_LOCATION,
        &mut stream,
        &[1],
        3
    )?;

    stream.seek(SeekFrom::Start(0)).unwrap();
    unpack_stream(&mut stream, 3, |idx, value| {
        result[idx] = value
    })?;

    assert_eq!(result[0], Some(-1.6));
    assert_eq!(result[1], None);
    assert_eq!(result[2], Some(5.4));
    Ok(())
}

More info

For further information and more examples, please see the rustdocs. Additional storage types are documented in the cql_db crate.