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76 lines
2.5 KiB
Rust
76 lines
2.5 KiB
Rust
// Any copyright is dedicated to the Public Domain.
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// http://creativecommons.org/publicdomain/zero/1.0/
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//! A demo that showcases the basic usage of iterators in rkv.
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//!
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//! You can test this out by running:
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//!
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//! cargo run --example iterator
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use std::{fs, str};
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use tempfile::Builder;
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use rkv::{
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backend::{SafeMode, SafeModeDatabase, SafeModeEnvironment},
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Manager, Rkv, SingleStore, StoreError, StoreOptions, Value,
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};
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fn main() {
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let root = Builder::new().prefix("iterator").tempdir().unwrap();
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fs::create_dir_all(root.path()).unwrap();
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let p = root.path();
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let mut manager = Manager::<SafeModeEnvironment>::singleton().write().unwrap();
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let created_arc = manager.get_or_create(p, Rkv::new::<SafeMode>).unwrap();
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let k = created_arc.read().unwrap();
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let store = k.open_single("store", StoreOptions::create()).unwrap();
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populate_store(&k, store).unwrap();
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let reader = k.read().unwrap();
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println!("Iterating from the beginning...");
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// Reader::iter_start() iterates from the first item in the store, and
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// returns the (key, value) tuples in order.
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let mut iter = store.iter_start(&reader).unwrap();
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while let Some(Ok((country, city))) = iter.next() {
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let country = str::from_utf8(country).unwrap();
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println!("{country}, {city:?}");
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}
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println!();
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println!("Iterating from the given key...");
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// Reader::iter_from() iterates from the first key equal to or greater
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// than the given key.
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let mut iter = store.iter_from(&reader, "Japan").unwrap();
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while let Some(Ok((country, city))) = iter.next() {
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println!("{}, {city:?}", str::from_utf8(country).unwrap());
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}
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println!();
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println!("Iterating from the given prefix...");
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let mut iter = store.iter_from(&reader, "Un").unwrap();
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while let Some(Ok((country, city))) = iter.next() {
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println!("{}, {city:?}", str::from_utf8(country).unwrap());
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}
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}
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fn populate_store(
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k: &Rkv<SafeModeEnvironment>,
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store: SingleStore<SafeModeDatabase>,
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) -> Result<(), StoreError> {
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let mut writer = k.write()?;
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for (country, city) in vec![
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("Canada", Value::Str("Ottawa")),
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("United States of America", Value::Str("Washington")),
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("Germany", Value::Str("Berlin")),
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("France", Value::Str("Paris")),
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("Italy", Value::Str("Rome")),
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("United Kingdom", Value::Str("London")),
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("Japan", Value::Str("Tokyo")),
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] {
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store.put(&mut writer, country, &city)?;
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}
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writer.commit()
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}
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