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_invalidations: 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 (issue #1571/#2059). A hit lets a repeated point read skip the Index.db interval parse. Since #2059 the key cache is ONE process-global instance shared by every open reader, so these counters are PROCESS-GLOBAL: they aggregate activity across ALL Database instances in the process, not one reader’s slice (a semantic change from the retired per-reader counters). Real counter; 0 before any reader touches the cache.

key_cache_misses: u64

Key cache misses (issue #1571/#2059). Process-global, like key_cache_hits — summed across all Database instances in the process.

key_cache_evictions: u64

Key cache evictions: entries evicted from the process-global key cache to stay within its byte budget (issue #1571/#2059) — DISTINCT from key_cache_invalidations.

key_cache_invalidations: u64

Key cache invalidations: entries dropped from the process-global key cache on generation removal / compaction / warm-registry evict (issue #2059) — a distinct counter from budget-driven key_cache_evictions.

key_cache_resident_bytes: usize

Key cache resident bytes: approximate resident footprint of the process-global key cache (issue #1571/#2059).

key_cache_capacity_bytes: usize

Key cache capacity bytes: the process-global key cache’s fixed configured byte budget (issue #1571/#2059), or 0 when block caching is disabled.

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.