Struct PartitionedCache

pub struct PartitionedCache<K1: Eq + Hash, K2: Eq + Hash, V> {
    partitions: HashMap<K1, Partition<K2, V>>,
    access_priority: PriorityQueue<K1, Reverse<Instant>>,
    expiry_priority: PriorityQueue<K1, Reverse<Instant>>,
    current_size: usize,
    desired_size: usize,
}

Fields

partitions: HashMap<K1, Partition<K2, V>>

Cached entries, indexed by partition key.

access_priority: PriorityQueue<K1, Reverse<Instant>>

Priority queue of partition keys ordered by access times.

When the cache is full and there are no expired records to prune, partitions will instead be pruned in LRU order.

INVARIANT: the keys in here are exactly the keys in partitions.

expiry_priority: PriorityQueue<K1, Reverse<Instant>>

Priority queue of partition keys ordered by expiry time.

When the cache is pruned, expired records are removed first.

INVARIANT: the keys in here are exactly the keys in partitions.

current_size: usize

The number of records in the cache, across all partitions.

INVARIANT: this is the sum of the size fields of the partitions.

desired_size: usize

The desired maximum number of records in the cache.

Implementations

impl<K1: Clone + Eq + Hash, K2: Copy + Eq + Hash, V: PartialEq> PartitionedCache<K1, K2, V>

pub fn new() -> Self

Create a new cache with a default desired size.

pub fn with_desired_size(desired_size: usize) -> Self

Create a new cache with the given desired size.

The prune method will remove expired records, and also enough records (in least-recently-used order) to get down to this size.

pub fn get_partition_without_checking_expiration( &mut self, partition_key: &K1, ) -> Option<&HashMap<K2, Vec<(V, Instant)>>>

Get all records for the given partition key from the cache, along with their expiration times.

These records may have expired if prune has not been called recently.

pub fn get_without_checking_expiration( &mut self, partition_key: &K1, record_key: &K2, ) -> Option<&[(V, Instant)]>

Get all records for the given partition and record key from the cache, along with their expiration times.

These records may have expired if prune has not been called recently.

pub fn upsert( &mut self, partition_key: K1, record_key: K2, value: V, ttl: Duration, )

Insert a record into the cache, or reset the expiry time if already present.

pub fn remove_expired(&mut self) -> usize

Delete all expired records.

Returns the number of records deleted.

pub fn prune(&mut self) -> (bool, usize, usize, usize)

Delete all expired records, and then enough least-recently-used records to reduce the cache to the desired size.

Returns (has overflowed?, current size, num expired, num pruned).

fn remove_expired_step(&mut self) -> usize

Helper for remove_expired: looks at the next-to-expire domain and cleans up expired records from it. This may delete more than one record, and may even delete the whole domain.

Returns the number of records removed.

fn remove_least_recently_used(&mut self) -> usize

Helper for prune: deletes all records associated with the least recently used domain.

Returns the number of records removed.

Trait Implementations

impl<K1: Clone + Eq + Hash, K2: Clone + Eq + Hash, V: Clone> Clone for PartitionedCache<K1, K2, V>

fn clone(&self) -> PartitionedCache<K1, K2, V>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<K1: Debug + Eq + Hash, K2: Debug + Eq + Hash, V: Debug> Debug for PartitionedCache<K1, K2, V>

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

Formats the value using the given formatter.

impl<K1: Clone + Eq + Hash, K2: Copy + Eq + Hash, V: PartialEq> Default for PartitionedCache<K1, K2, V>

fn default() -> Self

Returns the “default value” for a type.