EC
3123
MySQLERRORNotableDDLHIGH confidence

ALTER TABLE not supported: foreign key rename requires table copy

Production Risk

Medium — table copy locks can affect availability during the operation.

What this means

A column involved in a foreign key constraint is being renamed, which requires a full table copy and cannot be done in-place.

Why it happens
  1. 1Renaming a column that is part of a FOREIGN KEY constraint while using ALGORITHM=INPLACE.
How to reproduce
trigger — this will error
trigger — this will error
ALTER TABLE child RENAME COLUMN fk_col TO new_fk_col, ALGORITHM=INPLACE;

expected output

ERROR 3123 (HY000): ALGORITHM=INPLACE is not supported. Reason: Renaming a column used in a foreign key requires table copy.

Fix

Use ALGORITHM=COPY

Use ALGORITHM=COPY
ALTER TABLE child RENAME COLUMN fk_col TO new_fk_col, ALGORITHM=COPY;

Why this works

Table copy allows the foreign key metadata to be updated.

What not to do

✕

Sources
Official documentation ↗

MySQL 8.0 — 3123 ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_FK_RENAME2

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