---
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
  - `id` string[]
  - `alterations` AlterColumnsEntry[], required — List of column alterations to perform
    - `path` string, required — Column path to alter
    - `data_type` object, required — 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 column names for the virtual column (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)

## Response `200`

Alter columns operation result

- AlterTableAlterColumnsResponse
  - `transaction_id` string — Optional transaction identifier
  - `version` integer, required — Version of the table after altering columns

## 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

- **2025-12-11** `6ad4337e3849` — 2 breaking, 2 warning, 4 info
  - added the new required request property `alterations/items/data_type`
  - added the new required request property `alterations/items/path`
  - removed the request property `alterations/items/cast_to`
  - removed the request property `alterations/items/column`
  - …4 more
- **2025-08-02** `89fbd6272646` — 1 info
  - endpoint added
- **2025-07-21** `6790486d1fac` — 1 breaking
  - api path removed without deprecation

[Change 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/6ad4337e3849/schema)