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lancedb/docs/src/js/classes/Session.md
Weston Pace ed640a76d9 feat: add take_offsets and take_row_ids (#2584) 
These operations have existed in lance for a long while and many users
need to drop down to lance for this capability. This PR adds the API and
implements it using filters (e.g. `_rowid IN (...)`) so that in doesn't
currently add any load to `BaseTable`. I'm not sure that is sustainable
as base table implementations may want to specialize how they handle
this method. However, I figure it is a good starting point.

In addition, unlike Lance, this API does not currently guarantee
anything about the order of the take results. This is necessary for the
fallback filter approach to work (SQL filters cannot guarantee result
order)
2025-08-15 06:48:24 -07:00

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@lancedb/lancedb • Docs

@lancedb/lancedb / Session

Class: Session

A session for managing caches and object stores across LanceDB operations.

Sessions allow you to configure cache sizes for index and metadata caches, which can significantly impact memory use and performance. They can also be re-used across multiple connections to share the same cache state.

Constructors

new Session()

new Session(indexCacheSizeBytes?, metadataCacheSizeBytes?): Session

Create a new session with custom cache sizes.

Parameters

  • index_cache_size_bytes: The size of the index cache in bytes. Index data is stored in memory in this cache to speed up queries. Defaults to 6GB if not specified.
  • metadata_cache_size_bytes: The size of the metadata cache in bytes. The metadata cache stores file metadata and schema information in memory. This cache improves scan and write performance. Defaults to 1GB if not specified.

Parameters

  • indexCacheSizeBytes?: null | bigint

  • metadataCacheSizeBytes?: null | bigint

Returns

Session

Methods

approxNumItems()

approxNumItems(): number

Get the approximate number of items cached in the session.

Returns

number

sizeBytes()

sizeBytes(): bigint

Get the current size of the session caches in bytes.

Returns

bigint

default()

static default(): Session

Create a session with default cache sizes.

This is equivalent to creating a session with 6GB index cache and 1GB metadata cache.

Returns

Session