ALTER TABLE command only reordering on metadata level

Use CREATE OR REPLACE TABLE or INSERT OVERWRITE TABLE instead.

Written by Vidhi Khaitan

Last published at: June 10th, 2025

Problem

You have a pre-existing Delta table and want to add a new column, '<new-column>'. When you use the following ALTER TABLE command, the reordering is only adjusted at the metadata level.

ALTER TABLE <table> ALTER COLUMN <new-column> AFTER <existing-column>;

 

Cause

ALTER TABLE affects the metadata level only. It does not change the physical layout of the parquet files underneath. Limiting its impact ensure metadata-only changes to the schema, such as renaming or dropping columns, do not incur costly rewrites of the underlying data files.

 

For more information, refer to the Update Delta Lake table schema (AWS | Azure | GCP) documentation.

 

Solution

To rewrite files with new column order taken into account, use either CREATE OR REPLACE TABLE or INSERT OVERWRITE TABLE instead of ALTER TABLE.

 

CREATE OR REPLACE TABLE

CREATE OR REPLACE TABLE <table> AS
SELECT <existing-column>, <new-column>, <other-existing-column>, ... -- desired column order
FROM <table>

 

INSERT OVERWRITE TABLE 

INSERT OVERWRITE TABLE <table>
SELECT <existing-column>, <new-column>, <other-existing-column>, ...
FROM <table>