Struct Session 

pub struct Session { /* private fields */ }

Re-export Lance Session and ObjectStoreRegistry for custom session creation A user session holds the runtime state for a crate::Dataset

A session will be created automatically when a Dataset is opened. However, you can manually create the session and provide it to the Dataset builder in order to share runtime state between multiple datasets.

This can be used to share caches between multiple datasets, increasing the hit rate and reducing the amount of memory used.

A session contains two different caches:

• The index cache is used to cache opened indices and will cache index data
• The metadata cache is used to cache a variety of dataset metadata (more details can be found in the performance guide

Implementations

impl Session

pub fn new( index_cache_size: usize, metadata_cache_size: usize, store_registry: Arc<ObjectStoreRegistry>, ) -> Session

Create a new session.

Parameters:

• index_cache_size: the size of the index cache.
• metadata_cache_size: the size of the metadata cache.
• store_registry: the object store registry to use when opening datasets. This determines which schemes are available, and also allows re-using object stores.

pub fn register_index_extension( &mut self, name: String, extension: Arc<dyn IndexExtension>, ) -> Result<(), Error>

Register a new index extension.

A name can only be registered once per type of index extension.

Parameters:

• name: the name of the extension.
• extension: the extension to register.

pub fn size_bytes(&self) -> u64

Return the current size of the session in bytes

Keep in mind that this is not trivial to compute, as we will need to walk the caches

pub fn approx_num_items(&self) -> usize

Get the approximate number of items in the session.

This is a rough estimate of the number of items in the session. It is not exact and is not guaranteed to be accurate.

pub fn store_registry(&self) -> Arc<ObjectStoreRegistry>

Get the object store registry.

pub async fn metadata_cache_stats(&self) -> CacheStats

Fetch statistics for the metadata cache

pub async fn index_cache_stats(&self) -> CacheStats

Fetch statistics for the index cache

Trait Implementations

impl Clone for Session

fn clone(&self) -> Session

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Session

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

Formats the value using the given formatter.

impl DeepSizeOf for Session

fn deep_size_of_children(&self, context: &mut Context) -> usize

Returns an estimation of the heap-managed storage of this object. This does not include the size of the object itself.

fn deep_size_of(&self) -> usize

Returns an estimation of a total size of memory owned by the object, including heap-managed storage.

impl Default for Session

fn default() -> Session

Returns the “default value” for a type.