Struct index::Tree

pub struct Tree { /* fields omitted */ }

A flash-sympathetic persistent lock-free B+ tree

Methods

impl Tree

fn start(config: Config) -> DbResult<Tree, ()>

Load existing or create a new Tree.

fn flush(&self) -> CacheResult<(), ()>

Flushes any pending IO buffers to disk to ensure durability.

fn get(&self, key: &[u8]) -> DbResult<Option<Vec<u8>>, ()>

Retrieve a value from the Tree if it exists.

fn cas(
    &self,
    key: Vec<u8>,
    old: Option<Vec<u8>>,
    new: Option<Vec<u8>>
) -> DbResult<(), Option<Vec<u8>>>

Compare and swap. Capable of unique creation, conditional modification, or deletion. If old is None, this will only set the value if it doesn't exist yet. If new is None, will delete the value if old is correct. If both old and new are Some, will modify the value if old is correct. If Tree is read-only, will do nothing.

Examples

use sled::{ConfigBuilder, Error};
let config = ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();

// unique creation
assert_eq!(t.cas(vec![1], None, Some(vec![1])), Ok(()));
assert_eq!(t.cas(vec![1], None, Some(vec![1])), Err(Error::CasFailed(Some(vec![1]))));

// conditional modification
assert_eq!(t.cas(vec![1], Some(vec![1]), Some(vec![2])), Ok(()));
assert_eq!(t.cas(vec![1], Some(vec![1]), Some(vec![2])), Err(Error::CasFailed(Some(vec![2]))));

// conditional deletion
assert_eq!(t.cas(vec![1], Some(vec![2]), None), Ok(()));
assert_eq!(t.get(&*vec![1]), Ok(None));

fn set(&self, key: Vec<u8>, value: Vec<u8>) -> DbResult<(), ()>

Set a key to a new value.

fn del(&self, key: &[u8]) -> DbResult<Option<Vec<u8>>, ()>

Delete a value, returning the last result if it existed.

Examples

let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![1]);
assert_eq!(t.del(&*vec![1]), Ok(Some(vec![1])));
assert_eq!(t.del(&*vec![1]), Ok(None));

fn scan(&self, key: &[u8]) -> Iter

Iterate over tuples of keys and values, starting at the provided key.

Examples

let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![10]);
t.set(vec![2], vec![20]);
t.set(vec![3], vec![30]);
let mut iter = t.scan(&*vec![2]);
assert_eq!(iter.next(), Some(Ok((vec![2], vec![20]))));
assert_eq!(iter.next(), Some(Ok((vec![3], vec![30]))));
assert_eq!(iter.next(), None);

fn iter(&self) -> Iter

Iterate over the tuples of keys and values in this tree.

Examples

let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![10]);
t.set(vec![2], vec![20]);
t.set(vec![3], vec![30]);
let mut iter = t.iter();
assert_eq!(iter.next(), Some(Ok((vec![1], vec![10]))));
assert_eq!(iter.next(), Some(Ok((vec![2], vec![20]))));
assert_eq!(iter.next(), Some(Ok((vec![3], vec![30]))));
assert_eq!(iter.next(), None);

Trait Implementations

impl<'a> IntoIterator for &'a Tree

type Item = DbResult<(Vec<u8>, Vec<u8>), ()>

The type of the elements being iterated over.

type IntoIter = Iter<'a>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Iter<'a>

Creates an iterator from a value.

impl Clone for Tree

fn clone(&self) -> Tree

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Send for Tree

impl Sync for Tree

impl Debug for Tree

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.