Struct InMemoryStore 

pub struct InMemoryStore { /* private fields */ }

In-memory state store using BTreeMap for sorted key access.

This state store is suitable for state that fits in memory. It uses BTreeMap which provides O(log n + k) prefix and range scans, making it efficient for join state and windowed aggregation lookups.

Performance Characteristics

• Get: O(log n), < 500ns typical
• Put: O(log n), may allocate
• Delete: O(log n)
• Prefix scan: O(log n + k) where k is matching entries
• Range scan: O(log n + k) where k is matching entries

Memory Usage

Keys and values are stored as owned Vec<u8> and Bytes respectively. Use size_bytes() to monitor memory usage.

Implementations

impl InMemoryStore

pub fn new() -> Self

Creates a new empty in-memory store.

pub fn with_capacity(_capacity: usize) -> Self

Creates a new in-memory store.

The capacity hint is accepted for API compatibility but has no effect — BTreeMap does not support pre-allocation.

pub fn capacity(&self) -> usize

Returns the number of entries in the store.

BTreeMap does not expose a capacity concept, so this returns the current entry count.

pub fn shrink_to_fit(&mut self)

No-op for API compatibility.

BTreeMap manages its own memory and does not support explicit shrinking.

Trait Implementations

impl Default for InMemoryStore

fn default() -> Self

Returns the “default value” for a type.

impl StateStore for InMemoryStore

fn get(&self, key: &[u8]) -> Option<Bytes>

Get a value by key.

fn put(&mut self, key: &[u8], value: &[u8]) -> Result<(), StateError>

Store a key-value pair.

fn delete(&mut self, key: &[u8]) -> Result<(), StateError>

Delete a key.

fn prefix_scan<'a>( &'a self, prefix: &'a [u8], ) -> Box<dyn Iterator<Item = (Bytes, Bytes)> + 'a>

Scan all keys with a given prefix.

fn range_scan<'a>( &'a self, range: Range<&'a [u8]>, ) -> Box<dyn Iterator<Item = (Bytes, Bytes)> + 'a>

Range scan between two keys (exclusive end).

fn contains(&self, key: &[u8]) -> bool

Check if a key exists.

fn size_bytes(&self) -> usize

Get approximate size in bytes.

fn len(&self) -> usize

Get the number of entries in the store.

fn snapshot(&self) -> StateSnapshot

Create a snapshot for checkpointing.

fn restore(&mut self, snapshot: StateSnapshot)

Restore from a snapshot.

fn clear(&mut self)

Clear all entries.

fn is_empty(&self) -> bool

Check if the store is empty.

fn flush(&mut self) -> Result<(), StateError>

Flush any pending writes to durable storage.

fn get_or_insert( &mut self, key: &[u8], default: &[u8], ) -> Result<Bytes, StateError>

Get a value or insert a default.