Struct MetadataCache 

pub struct MetadataCache { /* private fields */ }

In-memory metadata cache for all segments.

Populated on startup from the segment catalog and updated as segments are created, compacted, or deleted.

Thread Safety

Uses RwLock<HashMap> for concurrent read access.

Capacity bound

An optional max_entries limit caps the number of cached segments. When the limit is reached, new inserts are still accepted (to keep hot metadata available) but a warning is emitted so operators can investigate. Each entry is ~1 KB, so even the default cap of 500 000 entries consumes at most ~500 MB — a safe upper bound for most deployments. Set max_entries = 0 to disable the cap.

Implementations

impl MetadataCache

pub fn new() -> Self

Create an empty metadata cache with the default capacity bound.

pub fn with_max_entries(max_entries: usize) -> Self

Create an empty metadata cache with a custom capacity bound.

Pass 0 to disable the capacity warning.

pub fn insert(&self, meta: CachedSegmentMeta)

Insert or update metadata for a segment.

If the cache exceeds max_entries a warning is logged but the insert still succeeds so that hot metadata is never silently dropped.

pub fn get(&self, segment_id: SegmentId) -> Option<Arc<CachedSegmentMeta>>

Look up metadata for a segment.

Returns an Arc for cheap cloning.

pub fn remove(&self, segment_id: SegmentId)

Remove metadata for a segment.

pub fn len(&self) -> usize

Returns the number of cached segments.

pub fn is_empty(&self) -> bool

Returns true if the cache is empty.

pub fn clear(&self)

Clear all cached metadata.

pub fn columns_for(&self, segment_id: SegmentId) -> Option<Vec<ColumnMeta>>

Returns column metadata for a segment, if cached.

Trait Implementations

impl Debug for MetadataCache

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

Formats the value using the given formatter.

impl Default for MetadataCache

fn default() -> Self

Returns the “default value” for a type.