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.

Operation | Database dimensions | Mean time (ns) --- | --- | --- Single point read | 1 | 3 100 (+/- 200) Single point read | 4 | 16 400 (+/- 900) Single point write | 1 | 2 800 (+/- 300) Single point write | 4 | 15 400 (+/- 1 000) Stream read 1 point | 1 | 2 500 (+/- 300) Stream read 1 point | 4 | 15 300 (+/- 800) Stream read 50 000 points | 1 | 27 300 000 (+/- 500 000) Stream read 50 000 points | 4 | 27 500 000 (+/- 150 000)

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 cqlnullablef64::{ NullableF64, unpack_stream };

const DATABASELOCATION: &str = "PATHTOYOURDATABASE_DIRECTORY";

pub fn examplecql() -> Result<(), Error> { // create a one dimensional database to hold 3 points cqldb::createdb::( DATABASELOCATION, &[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.