---
title: "Trigger an async column backfill job"
method: POST
path: "/v1/table/{id}/backfill_column"
tags: ["Table", "Data"]
---

# Trigger an async column backfill job

`POST /v1/table/{id}/backfill_column`

Trigger an asynchronous backfill job for a computed column on table `id`.
The column must be a virtual (UDF-backed) column. Returns a job ID for tracking.

## Path parameters

- `id` string, required

## Query parameters

- `delimiter` string

## Request body

- AlterTableBackfillColumnsRequest
  - `identity` Identity — Identity information of a request.
    - `api_key` string — API key for authentication. REST NAMESPACE ONLY This is passed via the `x-api-key` header.
    - `auth_token` string — Bearer token for authentication. REST NAMESPACE ONLY This is passed via the `Authorization` header with the Bearer scheme (e.g., `Bearer <token>`).
  - `context` unknown
  - `id` string[] — Table identifier path (namespace + table name)
  - `branch` string — Branch to target. When not specified, the main branch is used.
  - `column` string, required — Lance field path to backfill. Nested fields use dot-separated segments; use backtick-quoted segments for literal dots and double backticks inside quoted segments. Use canonical full paths for display and errors; leaf names alone only identify top-level fields; invalid or unresolved paths should return InvalidInput or TableColumnNotFound.
  - `where` string, nullable — Optional WHERE clause filter
  - `concurrency` integer, nullable — Optional concurrency override
  - `intra_applier_concurrency` integer, nullable — Optional intra-applier concurrency override
  - `min_checkpoint_size` integer, nullable — Optional minimum checkpoint size
  - `max_checkpoint_size` integer, nullable — Optional maximum checkpoint size
  - `batch_checkpoint_flush_interval_seconds` number, nullable — Optional batch checkpoint flush interval in seconds
  - `read_version` integer, nullable — Optional table version to read from
  - `task_size` integer, nullable — Optional task size
  - `num_frags` integer, nullable — Optional number of fragments
  - `checkpoint_size` integer, nullable — Optional checkpoint size
  - `commit_granularity` integer, nullable — Optional commit granularity
  - `cluster` string, nullable — Optional cluster name
  - `manifest` string, nullable — Optional manifest name

## Response `202`

Backfill job accepted

- AlterTableBackfillColumnsResponse
  - `context` unknown
  - `job_id` string, required — The job ID for tracking the backfill job

## Other responses

- `400` — Indicates a bad request error. It could be caused by an unexpected request body format or other forms of request validation failure, such as invalid json. Usually serves application/json content, although in some cases simple text/plain content might be returned by the server's middleware.
- `401` — Unauthorized. The request lacks valid authentication credentials for the operation.
- `403` — Forbidden. Authenticated user does not have the necessary permissions.
- `404` — A server-side problem that means can not find the specified resource.
- `503` — The service is not ready to handle the request. The client should wait and retry. The service may additionally send a Retry-After header to indicate when to retry.
- `5XX` — A server-side problem that might not be addressable from the client side. Used for server 5xx errors without more specific documentation in individual routes.

---

[API](https://skmtc.net/lance-format/apis/lance-namespace-specification.md) · [All operations](https://skmtc.net/lance-format/apis/lance-namespace-specification/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/lance-format/lance-namespace-specification/versions/f09656f7f568/schema)