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// Any copyright is dedicated to the Public Domain.
//! A demo that showcases the basic usage of iterators in rkv.
//!
//! You can test this out by running:
//!
//! cargo run --example iterator
use std::{fs, str};
use tempfile::Builder;
use rkv::{
backend::{SafeMode, SafeModeDatabase, SafeModeEnvironment},
Manager, Rkv, SingleStore, StoreError, StoreOptions, Value,
};
fn main() {
let root = Builder::new().prefix("iterator").tempdir().unwrap();
fs::create_dir_all(root.path()).unwrap();
let p = root.path();
let mut manager = Manager::<SafeModeEnvironment>::singleton().write().unwrap();
let created_arc = manager.get_or_create(p, Rkv::new::<SafeMode>).unwrap();
let k = created_arc.read().unwrap();
let store = k.open_single("store", StoreOptions::create()).unwrap();
populate_store(&k, store).unwrap();
let reader = k.read().unwrap();
println!("Iterating from the beginning...");
// Reader::iter_start() iterates from the first item in the store, and
// returns the (key, value) tuples in order.
let mut iter = store.iter_start(&reader).unwrap();
while let Some(Ok((country, city))) = iter.next() {
let country = str::from_utf8(country).unwrap();
println!("{country}, {city:?}");
}
println!();
println!("Iterating from the given key...");
// Reader::iter_from() iterates from the first key equal to or greater
// than the given key.
let mut iter = store.iter_from(&reader, "Japan").unwrap();
while let Some(Ok((country, city))) = iter.next() {
println!("{}, {city:?}", str::from_utf8(country).unwrap());
}
println!();
println!("Iterating from the given prefix...");
let mut iter = store.iter_from(&reader, "Un").unwrap();
while let Some(Ok((country, city))) = iter.next() {
println!("{}, {city:?}", str::from_utf8(country).unwrap());
}
}
fn populate_store(
k: &Rkv<SafeModeEnvironment>,
store: SingleStore<SafeModeDatabase>,
) -> Result<(), StoreError> {
let mut writer = k.write()?;
for (country, city) in vec![
("Canada", Value::Str("Ottawa")),
("United States of America", Value::Str("Washington")),
("Germany", Value::Str("Berlin")),
("France", Value::Str("Paris")),
("Italy", Value::Str("Rome")),
("United Kingdom", Value::Str("London")),
("Japan", Value::Str("Tokyo")),
] {
store.put(&mut writer, country, &city)?;
}
writer.commit()
}