Crate cql_u64

This crate implements various CqlType derivatives for storing u64 values in a CQL database.

Will allocate 8 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 _unchecked (ns)	Mean time (ns)
Single point read	1	2 450 (+/- 300)	7 500 (+/- 600)
Single point read	4	14 850 (+/- 1 000)	37 550 (+/- 2 300)
Single point write	1	2 800 (+/- 400)	7 700 (+/- 400)
Single point write	4	15 400 (+/- 2 500)	37 700 (+/- 3 000)
Stream read 1 point	1	2 500 (+/- 300)	10 000 (+/- 850)
Stream read 1 point	4	14 900 (+/- 600)	42 500 (+/- 6 500)
Stream read 50 000 points	1	27 650 000 (+/- 31 000)	27 630 000 (+/- 180 000)
Stream read 50 000 points	4	27 660 000 (+/- 1 200 000)	27 620 000 (+/- 480 000)

Examples

The following creates a 1D database, writes 2 values to it, and then streams them into an array.

const N_VALUES_TO_READ: usize = 3;

let base_point = [1];
let value1 = 1;
let value3 = 5;

cql_db::create_db::<U64>(
    DATABASE_LOCATION,
    &[3]
)?;

cql_db::write_value::<U64>(
    DATABASE_LOCATION,
    &base_point,
    value1
)?;

cql_db::write_value::<U64>(
    DATABASE_LOCATION,
    &[base_point[0] + 2],
    value3
)?;

let mut result = [0; N_VALUES_TO_READ];
let mut stream = Cursor::new(Vec::new());

cql_db::read_to_stream::<U64>(
    DATABASE_LOCATION,
    &mut stream,
    &base_point,
    N_VALUES_TO_READ as u64
)?;

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

assert_eq!(result[0], value1);
assert_eq!(result[1], 0);
assert_eq!(result[2], value3);

Structs

U64

Static struct for declaring that you want to work with u64 values in a CQL database.

Functions

unpack_stream

Unpacks n_values of u64 from a stream, calling value_handler with each value and it’s index.