Struct fjall::TransactionalPartitionHandle

pub struct TransactionalPartitionHandle { /* private fields */ }

Access to a partition of a transactional keyspace

Implementations

impl TransactionalPartitionHandle

pub fn path(&self) -> PathBuf

Returns the underlying LSM-tree’s path

pub fn take<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<UserValue>>

Removes an item and returns its value if it existed.

The operation will run wrapped in a transaction.

partition.insert("a", "abc")?;

let taken = partition.take("a")?.unwrap();
assert_eq!(b"abc", &*taken);

let item = partition.get("a")?;
assert!(item.is_none());

Errors

Will return Err if an IO error occurs.

pub fn fetch_update<K: AsRef<[u8]>, F: Fn(Option<&UserValue>) -> Option<UserValue>>( &self, key: K, f: F, ) -> Result<Option<UserValue>>

Atomically updates an item and returns the previous value.

Returning None removes the item if it existed before.

The operation will run wrapped in a transaction.

Examples

partition.insert("a", "abc")?;

let prev = partition.fetch_update("a", |_| Some(Slice::from(*b"def")))?.unwrap();
assert_eq!(b"abc", &*prev);

let item = partition.get("a")?;
assert_eq!(Some("def".as_bytes().into()), item);

partition.insert("a", "abc")?;

let prev = partition.fetch_update("a", |_| None)?.unwrap();
assert_eq!(b"abc", &*prev);

let item = partition.get("a")?;
assert!(item.is_none());

Errors

Will return Err if an IO error occurs.

pub fn update_fetch<K: AsRef<[u8]>, F: Fn(Option<&UserValue>) -> Option<UserValue>>( &self, key: K, f: F, ) -> Result<Option<UserValue>>

Atomically updates an item and returns the new value.

Returning None removes the item if it existed before.

The operation will run wrapped in a transaction.

Examples

partition.insert("a", "abc")?;

let updated = partition.update_fetch("a", |_| Some(Slice::from(*b"def")))?.unwrap();
assert_eq!(b"def", &*updated);

let item = partition.get("a")?;
assert_eq!(Some("def".as_bytes().into()), item);

partition.insert("a", "abc")?;

let updated = partition.update_fetch("a", |_| None)?;
assert!(updated.is_none());

let item = partition.get("a")?;
assert!(item.is_none());

Errors

Will return Err if an IO error occurs.

pub fn insert<K: AsRef<[u8]>, V: AsRef<[u8]>>( &self, key: K, value: V, ) -> Result<()>

Inserts a key-value pair into the partition.

Keys may be up to 65536 bytes long, values up to 2^32 bytes. Shorter keys and values result in better performance.

If the key already exists, the item will be overwritten.

The operation will run wrapped in a transaction.

Examples

partition.insert("a", "abc")?;

assert!(!keyspace.read_tx().is_empty(&partition)?);

Errors

Will return Err if an IO error occurs.

pub fn remove<K: AsRef<[u8]>>(&self, key: K) -> Result<()>

Removes an item from the partition.

The key may be up to 65536 bytes long. Shorter keys result in better performance.

The operation will run wrapped in a transaction.

Examples

partition.insert("a", "abc")?;
assert!(!keyspace.read_tx().is_empty(&partition)?);

partition.remove("a")?;
assert!(keyspace.read_tx().is_empty(&partition)?);

Errors

Will return Err if an IO error occurs.

pub fn get<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<UserValue>>

Retrieves an item from the partition.

The operation will run wrapped in a read snapshot.

Examples

partition.insert("a", "my_value")?;

let item = partition.get("a")?;
assert_eq!(Some("my_value".as_bytes().into()), item);

Errors

Will return Err if an IO error occurs.

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

Returns true if the partition contains the specified key.

The operation will run wrapped in a read snapshot.

Examples

partition.insert("a", "my_value")?;

assert!(partition.contains_key("a")?);
assert!(!partition.contains_key("b")?);

Errors

Will return Err if an IO error occurs.

Trait Implementations

impl Clone for TransactionalPartitionHandle

fn clone(&self) -> TransactionalPartitionHandle

Returns a copy of the value.

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

Performs copy-assignment from source.

impl GarbageCollection for TransactionalPartitionHandle

fn gc_scan(&self) -> Result<GcReport>

Collects statistics about blob fragmentation inside the partition.

fn gc_with_space_amp_target(&self, factor: f32) -> Result<u64>

Rewrites blobs in order to achieve the given space amplification factor.

fn gc_with_staleness_threshold(&self, threshold: f32) -> Result<u64>

Rewrites blobs that have reached a given staleness threshold.

fn gc_drop_stale_segments(&self) -> Result<u64>

Drops fully stale segments.