Fast-Forward

⏩ Quering lists blazing fast.

This is a very, very, ... early state. This means, this implementation is on the way to find out, what is a good solution and want anyone use it. The API can change a lot! Please, try it out and give me feedback.

Overview

Fast-Forward is a library for finding or filtering items in a (large) collection (Vec, Slice, Map, ...). This means faster than an Iterator or a search algorithm. It is a wrapper, which extends the given collection with very fast find operations. This wrapper is just as easy to use as the given (original) collection.

This faster is achieved by using Indices. This means, it does not have to touch and compare every item in the collection.

An Index has two parts, a Key (item to searching for) and a Position (the index) in the collection.

Example for an indexed read only List (ro::IList):

use fast_forward::{index::UIntIndex, collections::ro::IList};

#[derive(Debug, PartialEq)]
pub struct Car(usize, String);

// created an indexed List with the UIntIndex on the Car property 0.
let l = IList::<UIntIndex, _>::new(|c: &Car| c.0, vec![
                            Car(1, "BMW".into()),
                            Car(2, "VW".into())]);

// idx method pointed to the Car.0 property Index and
// gives access to the `Retriever` object to handle queries, like: contains, get, filter.
assert!(l.idx().contains(&2));
assert!(!l.idx().contains(&2000));

// get a Car with the ID = 2
assert_eq!(l.idx().get(&2).next(), Some(&Car(2, "VW".into())));

// get many Cars with ID = 2 or 1
assert_eq!(
    l.idx().get_many([2, 1]).collect::<Vec<_>>(),
    vec![&Car(2, "VW".into()), &Car(1, "BMW".into())],
);

// the same query with the filter-method
// (which has the disadvantage, that this need a allocation)
assert_eq!(
    l.idx().filter(|f| f.eq(&2) | f.eq(&1)).collect::<Vec<_>>(),
    vec![&Car(1, "BMW".into()), &Car(2, "VW".into())],
);

// you can use the Vec methods too
assert_eq!(2, l.len());

// or you can get MetaData like min and max Key value
use fast_forward::index::store::MetaData;

assert_eq!(1, l.idx().meta().min_key());
assert_eq!(2, l.idx().meta().max_key());

All supported options for retrieve Items can you find by the crate::collections::Retriever struct.

Example for a View of an indexed read only List (ro::IList):

A View is like a database view. This means you get a subset of items, which you can see. It is useful, if you don't want to give full read access to the complete collection.

All details to [crate::collections::Retriever::create_view()]

use fast_forward::{index::MapIndex, collections::ro::IList};

#[derive(Debug, PartialEq)]
pub struct Car(usize, String);

// created an indexed List with the MapIndex on the Car property 1.
let l = IList::<MapIndex, _>::new(|c: &Car| c.1.clone(), vec![
                            Car(1, "BMW".into()),
                            Car(2, "VW".into()),
                            Car(3, "Audi".into())]);

// create a view: only for Car Name = "BMW" 0r "Audi"
let view = l.idx().create_view([String::from("BMW"), String::from("Audi")]);

// Car with Name "VW" is NOT in the view
assert!(!view.contains(&String::from("VW")));

// get the Care with the name "Audi"
assert_eq!(
    view.get(&String::from("Audi")).collect::<Vec<_>>(),
    vec![&Car(3, "Audi".into())],
);

// the original list contains of course the Car with ID "VW"
assert!(l.idx().contains(&String::from("VW")));

License: MIT