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.

Size

One entry per live segment, and memory_bytes reports what they cost. The figure is maintained as entries are inserted and removed rather than recomputed, because statistics() runs on every metrics scrape and walking the map there would make the exporter the most expensive thing in the process.

Implementations

impl MetadataCache

pub fn new() -> Self

Create an empty metadata index.

pub fn insert(&self, meta: CachedSegmentMeta)

Insert or update metadata for a segment.

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 memory_bytes(&self) -> usize

Bytes the index holds, counted as entries come and go.

Summed into the database’s resident-memory total and exported as chronix_metadata_cache_bytes.

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.