Update from code changes: document declared computed columns by mintlify[bot] · Pull Request #330 · lancedb/docs

mintlify · 2026-08-14T21:21:43Z

Summary

add_columns now accepts a SQL expression declaration that commits the column empty and is filled by a later refresh_column call (blocking) or refresh_column_async (returns a job handle) across Python, TypeScript, and Rust. Computed columns work on both local tables and LanceDB Enterprise, with the refresh on Enterprise running as a server-side backfill job that must be submitted through the async form. Several computed columns can be declared in one call and reference each other in dependency order, and expressions can read Blob API columns on local tables. The docs page for schema evolution gains "Declare computed columns" and "Refresh a computed column" subsections covering the APIs, when to use them, the local vs. Enterprise behavior, and the write and schema-change restrictions the declaration imposes.

Changes

Added a "Declare computed columns" subsection under "Add new columns" in docs/tables/schema.mdx with Python, TypeScript, and Rust examples and callouts for local vs. Enterprise behavior and the transform-vs-computed restriction.
Added a "Declare several computed columns at once" subsection covering batched, dependency-ordered declarations in a single add_columns call.
Added a "Reference blob columns" subsection noting that expressions can read Blob API columns, that a direct projection inherits blob semantics on the output, and that Enterprise support ships with the server planner rollout.
Added a "Refresh a computed column" subsection covering refresh_column / refreshColumn, the returned row count and version, idempotency, the LSM and Enterprise refusals for the blocking form, and the refusal when a computed input still has rows to fill.
Added a "Run the refresh in the background" subsection covering refresh_column_async / refreshColumnAsync, the returned job handle, the fact that invalid input is reported by the submitting call rather than by the job, and the read-freshness baseline the successful wait establishes on Enterprise.

Update history

Documented add_columns(computed=...) / addColumns({ computed }) / .add_columns().computed(...) declaration API (source: feat: declare computed columns by SQL expression lancedb#3937).
Documented refresh_column / refreshColumn for filling declared computed columns (source: feat: refresh computed columns lancedb#3938).
Documented refresh_column_async / refreshColumnAsync returning a job handle for background refreshes (source: feat: refresh_column_async returns a job handle lancedb#3939).
Documented computed columns on LanceDB Enterprise, including that blocking refresh is refused on remote tables and that a successful async wait establishes a read-freshness baseline on the handle (source: feat: computed columns on remote tables lancedb#3941).
Documented batched dependent computed column declarations in one add_columns call and the refresh-order requirement that refuses a dependent refresh while its input still has rows to fill (source: feat: let a computed-column batch read its own earlier declarations lancedb#4072).
Documented that computed column expressions can read Blob API columns, that a direct projection inherits blob semantics on the output, and that Enterprise support ships with the server planner rollout (source: feat: support blob computed column refresh lancedb#4081).

mintlify · 2026-08-14T21:21:47Z

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mintlify · 2026-08-14T21:45:59Z