Struct Tree

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pub struct Tree { /* private fields */ }

Expand description

atomic lock-free tree A flash-sympathetic persistent lock-free B+ tree

Implementations§

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impl Tree

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

Load existing or create a new Tree.

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

Flushes any pending IO buffers to disk to ensure durability.

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

Retrieve a value from the Tree if it exists.

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pub 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));

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

Set a key to a new value.

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pub 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));

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pub 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);

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pub 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);