[][src]Struct sled::Tree

pub struct Tree { /* fields omitted */ }

A flash-sympathetic persistent lock-free B+ tree

Methods

impl Tree
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Load existing or create a new Tree with a default configuration.

Load existing or create a new Tree.

Flushes any pending IO buffers to disk to ensure durability.

Retrieve a value from the Tree if it exists.

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));

Set a key to a new value, returning the old value if it was set.

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).unwrap().unwrap(), 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).unwrap().unwrap(), vec![4]);

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]).unwrap().unwrap(), vec![1]);
assert_eq!(t.del(&*vec![1]), Ok(None));

Important traits for Iter<'a>

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>

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 Sync for Tree
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impl Send for Tree
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impl Clone for Tree
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Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl<'a> IntoIterator for &'a Tree
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The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Important traits for Iter<'a>

Creates an iterator from a value. Read more

impl Debug for Tree
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Formats the value using the given formatter. Read more

Blanket Implementations

impl<T, U> Into for T where
    U: From<T>, 
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Performs the conversion.

impl<T> ToOwned for T where
    T: Clone
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Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<T> From for T
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Performs the conversion.

impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from)

Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized
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Immutably borrows from an owned value. Read more

impl<T> BorrowMut for T where
    T: ?Sized
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Mutably borrows from an owned value. Read more

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from)

The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from)

Performs the conversion.

impl<T> Any for T where
    T: 'static + ?Sized
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🔬 This is a nightly-only experimental API. (get_type_id)

this method will likely be replaced by an associated static

Gets the TypeId of self. Read more