Struct sled::Tree
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pub struct Tree { /* fields omitted */ }
A flash-sympathetic persistent lock-free B+ tree
Methods
impl Tree
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pub fn start(config: Config) -> DbResult<Tree, ()>
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Load existing or create a new Tree
.
pub fn flush(&self) -> CacheResult<(), ()>
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Flushes any pending IO buffers to disk to ensure durability.
pub fn get(&self, key: &[u8]) -> DbResult<Option<Vec<u8>>, ()>
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Retrieve a value from the Tree
if it exists.
pub fn cas(
&self,
key: Vec<u8>,
old: Option<Vec<u8>>,
new: Option<Vec<u8>>
) -> DbResult<(), Option<Vec<u8>>>
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&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));
pub fn set(&self, key: Vec<u8>, value: Vec<u8>) -> DbResult<(), ()>
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Set a key to a new value.
pub fn merge(&self, key: Vec<u8>, value: Vec<u8>) -> DbResult<(), ()>
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Merge a new value into the total state for a key.
Examples
fn concatenate_merge( _key: &[u8], // the key being merged old_value: Option<&[u8]>, // the previous value, if one existed merged_bytes: &[u8] // the new bytes being merged in ) -> Option<Vec<u8>> { // set the new value, return None to delete let mut ret = old_value .map(|ov| ov.to_vec()) .unwrap_or_else(|| vec![]); ret.extend_from_slice(merged_bytes); Some(ret) } let config = sled::ConfigBuilder::new() .temporary(true) .merge_operator(concatenate_merge) .build(); let tree = sled::Tree::start(config).unwrap(); let k = b"k1".to_vec(); tree.set(k.clone(), vec![0]); tree.merge(k.clone(), vec![1]); tree.merge(k.clone(), vec![2]); assert_eq!(tree.get(&k), Ok(Some(vec![0, 1, 2]))); // sets replace previously merged data, // bypassing the merge function. tree.set(k.clone(), vec![3]); assert_eq!(tree.get(&k), Ok(Some(vec![3]))); // merges on non-present values will add them tree.del(&k); tree.merge(k.clone(), vec![4]); assert_eq!(tree.get(&k), Ok(Some(vec![4])));
pub fn del(&self, key: &[u8]) -> DbResult<Option<Vec<u8>>, ()>
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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));
ⓘImportant traits for Iter<'a>pub fn scan(&self, key: &[u8]) -> Iter
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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);
ⓘImportant traits for Iter<'a>pub fn iter(&self) -> Iter
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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
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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?
ⓘImportant traits for Iter<'a>fn into_iter(self) -> Iter<'a>
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Creates an iterator from a value. Read more
impl Clone for Tree
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fn clone(&self) -> Tree
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Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
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Performs copy-assignment from source
. Read more