Trait FileMetadataCache 

pub trait FileMetadataCache: CacheAccessor<Path, CachedFileMetadataEntry> {
    // Required methods
    fn cache_limit(&self) -> usize;
    fn update_cache_limit(&self, limit: usize);
    fn list_entries(&self) -> HashMap<Path, FileMetadataCacheEntry>;
}

Cache for file-embedded metadata.

This cache stores per-file metadata in the form of CachedFileMetadataEntry, which includes the ObjectMeta for validation.

For example, the built in ListingTable uses this cache to avoid parsing Parquet footers multiple times for the same file.

DataFusion provides a default implementation, DefaultFilesMetadataCache, and users can also provide their own implementations to implement custom caching strategies.

The typical usage pattern is:

1. Call get(path) to check for cached value
2. If Some(cached), validate with cached.is_valid_for(&current_meta)
3. If invalid or missing, compute new value and call put(path, new_value)

See crate::runtime_env::RuntimeEnv for more details.

Required Methods

fn cache_limit(&self) -> usize

Returns the cache’s memory limit in bytes.

fn update_cache_limit(&self, limit: usize)

Updates the cache with a new memory limit in bytes.

fn list_entries(&self) -> HashMap<Path, FileMetadataCacheEntry>

Retrieves the information about the entries currently cached.

Trait Implementations

impl Debug for dyn FileMetadataCache

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

Formats the value using the given formatter.

Implementors

impl FileMetadataCache for DefaultFilesMetadataCache