---
title: "Modify existing columns"
method: POST
path: "/v1/table/{id}/alter_columns"
tags: ["Table", "Metadata"]
---

# Modify existing columns

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

Modify existing columns in table `id`, such as renaming or changing data types.

## Path parameters

- `id` string, required

## Query parameters

- `delimiter` string

## Request body

- AlterTableAlterColumnsRequest
  - `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.
  - `alterations` AlterColumnsEntry[], required — List of column alterations to apply to the table
    - `path` string, required — Lance field path to alter. 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.
    - `data_type` object — New data type for the column using JSON representation (optional)
    - `rename` string, nullable — New name for the column (optional)
    - `nullable` boolean, nullable — Whether the column should be nullable (optional)
    - `virtual_column` AlterVirtualColumnEntry
      - `input_columns` string[], nullable — List of input Lance field paths for the virtual column. Nested fields use dot-separated segments; use backtick-quoted segments for literal dots and double backticks inside quoted segments. Optional.
      - `image` string, nullable — Docker image to use for the UDF (optional)
      - `udf` string, nullable — Base64 encoded pickled UDF (optional)
      - `udf_name` string, nullable — Name of the UDF (optional)
      - `udf_version` string, nullable — Version of the UDF (optional)
      - `udf_backend` string, nullable — UDF backend type (e.g. DockerUDFSpecV1) (optional)
      - `auto_backfill` boolean, nullable — Whether to automatically backfill the column (optional)
      - `manifest` string, nullable — JSON-serialized manifest for the UDF environment (optional)
      - `manifest_checksum` string, nullable — SHA-256 checksum of the manifest content (optional)
      - `field_metadata` unknown

## Response `200`

Alter columns operation result

- AlterTableAlterColumnsResponse
  - `context` unknown
  - `version` integer, required — The commit version associated with the operation

## 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.

## Changes

- **2026-07-01** `591cd95574b0` — 8 info
  - added the new optional request property `context`
  - added the optional property `context` to the response with the `200` status
  - added the optional property `context` to the response with the `400` status
  - added the optional property `context` to the response with the `401` status
  - …4 more
- **2026-06-10** `a3308034a3cd` — 2 breaking
  - the `alterations/items/path` request property's minLength was increased from `0` to `1`
  - the `alterations/items/virtual_column/input_columns/items/` request property's minLength was increased from `0` to `1`
- **2026-06-05** `9932582b6bd7` — 1 info
  - added the new optional request property `branch`
- **2026-05-05** `ba14cdd902a7` — 1 info
  - the request property `alterations/items/data_type` became optional
- **2026-05-05** `d38d5bb3876c` — 6 info
  - added the new optional request property `alterations/items/virtual_column/auto_backfill`
  - added the new optional request property `alterations/items/virtual_column/field_metadata`
  - added the new optional request property `alterations/items/virtual_column/manifest`
  - added the new optional request property `alterations/items/virtual_column/manifest_checksum`
  - …2 more

[Full history](https://skmtc.dev/lance-format/apis/lance-namespace-specification/changes/v1/table/:id/alter_columns/post.md)

---

[API](https://skmtc.dev/lance-format/apis/lance-namespace-specification.md) · [All operations](https://skmtc.dev/lance-format/apis/lance-namespace-specification/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/lance-format/lance-namespace-specification/revisions/541331733d0c/schema)