Struct MemoryStats 

pub struct MemoryStats {

    pub block_cache_hits: u64,
    pub block_cache_misses: u64,
    pub block_cache_evictions: u64,
    pub block_cache_capacity_bytes: usize,
    pub key_cache_hits: u64,
    pub key_cache_misses: u64,
    pub key_cache_evictions: u64,
    pub key_cache_resident_bytes: usize,
    pub key_cache_capacity_bytes: usize,
    pub row_cache_hits: u64,
    pub row_cache_misses: u64,
    pub total_memory_used: usize,
    pub buffer_allocations: u64,
    pub buffer_deallocations: u64,
}

Memory statistics.

Public-surface-wired (semver) through Database::stats().memory_stats. The field names and types are preserved verbatim (issue #1568, AK6); only the source of the block-cache numbers changed — they now reflect the real B1 DecompressedChunkCache.

Independent sampling (advisory observability)

The block_cache_* fields and the key_cache_* fields are sampled independently and at different instants: the block-cache figures come from the MemoryManager (its shared B1 chunk cache), while the key-cache figures are aggregated from the storage engine’s per-reader B4 caches (SSTableManager::aggregate_key_cache_stats) in a separate step. Under concurrent read load the two groups can therefore reflect slightly different moments in time, so within a single memory_stats snapshot the block-cache vs key-cache figures are not guaranteed to be mutually coherent. Treat this as advisory observability (trends, rough ratios), not a transactionally-consistent point-in-time view of both caches.

Fields

block_cache_hits: u64

Block cache hits (real B1 cache hit count when wired).

block_cache_misses: u64

Block cache misses (real B1 cache miss count when wired).

block_cache_evictions: u64

Block cache evictions: entries the B1 decompressed-chunk cache evicted to stay within its byte budget (issue #1571, B5). Real eviction_count() when wired; 0 (honest — no cache, no evictions) otherwise. High churn relative to hits signals an undersized block_cache_capacity_bytes.

block_cache_capacity_bytes: usize

Block cache configured byte budget (issue #1571, B5): the B1 cache’s budget_bytes() when wired, so a hit rate can be read against the budget it was measured under; 0 when no cache is wired / block caching disabled.

key_cache_hits: u64

Key cache hits: aggregate across the per-reader B4 key→partition-offset caches (issue #1571, B5). A hit lets a repeated point read skip the Index.db/trie descent. Real summed counter; 0 when no reader is open.

key_cache_misses: u64

Key cache misses: aggregate across the per-reader B4 caches (issue #1571).

key_cache_evictions: u64

Key cache evictions: aggregate across the per-reader B4 caches (issue #1571) — entries evicted to stay within each reader’s byte budget.

key_cache_resident_bytes: usize

Key cache resident bytes: aggregate approximate resident footprint of the per-reader B4 caches (issue #1571).

key_cache_capacity_bytes: usize

Key cache capacity bytes: summed configured byte budget across the per-reader B4 caches (issue #1571).

row_cache_hits: u64

Row cache hits. Retained for shape compatibility; the row cache was deleted (issue #1568), so this reports 0 (full surface is Epic B / B5).

row_cache_misses: u64

Row cache misses. Retained for shape compatibility; reports 0.

total_memory_used: usize

Total memory used. Now the B1 cache’s resident decompressed bytes (resident_bytes()) when wired (issue #1568).

buffer_allocations: u64

Buffer pool allocations. Retained for shape compatibility; the buffer pool was deleted (issue #1568), so this reports 0.

buffer_deallocations: u64

Buffer pool deallocations. Retained for shape compatibility; reports 0.

Implementations

impl MemoryStats

pub fn block_cache_hit_rate(&self) -> f64

Calculate block cache hit rate.

pub fn key_cache_hit_rate(&self) -> f64

Calculate the aggregate key-cache hit rate (issue #1571, B5) from the real summed hit and miss counts. Returns 0.0 when there has been no key-cache activity (honest — not a structural pin).

pub fn row_cache_hit_rate(&self) -> f64

Calculate row cache hit rate.

Trait Implementations

impl Clone for MemoryStats

fn clone(&self) -> MemoryStats

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MemoryStats

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

Formats the value using the given formatter.

impl Default for MemoryStats

fn default() -> MemoryStats

Returns the “default value” for a type.