Struct SledTreeOverlay 

pub struct SledTreeOverlay {
    pub tree: Tree,
    pub state: SledTreeOverlayState,
    /* private fields */
}

An overlay on top of a single sled::Tree instance.

Fields

tree: Tree

The sled::Tree that is being overlayed.

state: SledTreeOverlayState

Current overlay cache state.

Implementations

impl SledTreeOverlay

pub fn new(tree: &Tree) -> Self

Instantiate a new SledTreeOverlay on top of a given sled::Tree.

pub fn contains_key(&self, key: &[u8]) -> Result<bool, Error>

Returns true if the overlay contains a value for a specified key.

pub fn is_empty(&self) -> bool

Returns true if the overlay is empty.

pub fn last(&self) -> Result<Option<(IVec, IVec)>, Error>

Returns last key and value from the overlay or None if its empty, based on the Ord implementation for Vec<u8>.

pub fn get(&self, key: &[u8]) -> Result<Option<IVec>, Error>

Retrieve a value from the overlay if it exists.

pub fn insert( &mut self, key: &[u8], value: &[u8], ) -> Result<Option<IVec>, Error>

Insert a key to a new value, returning the last value if it was set.

pub fn remove(&mut self, key: &[u8]) -> Result<Option<IVec>, Error>

Delete a value, if it exists, returning the old value.

pub fn clear(&mut self) -> Result<(), Error>

Removes all values from the cache and marks all tree records as removed.

pub fn aggregate(&self) -> Option<Batch>

Aggregate all the current overlay changes into a sled::Batch ready for further operation. If there are no changes, return None.

pub fn checkpoint(&mut self)

Checkpoint current cache state so we can revert to it, if needed.

pub fn revert_to_checkpoint(&mut self)

Revert to current cache state checkpoint.

pub fn diff( &self, sequence: &[SledTreeOverlayStateDiff], ) -> Result<SledTreeOverlayStateDiff, Error>

Calculate differences from provided overlay state changes sequence. This can be used when we want to keep track of consecutive individual changes performed over the current overlay state. If the sequence is empty, current state is returned as the diff.

pub fn add_diff(&mut self, diff: &SledTreeOverlayStateDiff)

Add provided tree overlay state changes from our own.

pub fn remove_diff(&mut self, diff: &SledTreeOverlayStateDiff)

Remove provided tree overlay state changes from our own.

pub fn iter(&self) -> SledTreeOverlayIter<'_>

Immutably iterate through the tree overlay.

Trait Implementations

impl Clone for SledTreeOverlay

fn clone(&self) -> SledTreeOverlay

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SledTreeOverlay

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

Formats the value using the given formatter.

impl<'a> IntoIterator for &'a SledTreeOverlay

Define fusion iteration behavior, allowing us to use the SledTreeOverlayIter iterator in loops directly, without using .iter() method of SledTreeOverlay.

type Item = Result<(IVec, IVec), Error>

The type of the elements being iterated over.

type IntoIter = SledTreeOverlayIter<'a>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.