Summary

Fix ChangeField failure with index+column type changes on MySQL.

Review Request #14922 — Created March 17, 2026 and updated March 17, 2026, 4:45 p.m.

Information

Owner

david

Repository

Django Evolution

Branch

master

Bugs

Depends On

Reviewers

Groups

django-evolution

People

Description

When a ChangeField mutation changes both the field type and
unique/db_index attributes, MySQL's MODIFY COLUMN runs before the
index is dropped. MySQL rejects this for TEXT or BLOB columns with
the error "BLOB/TEXT column used in key specification without a key
length".

This happened because ChangeField.mutate() returns early after
change_column_type() when change_column_type_sets_attrs is True
(MySQL), skipping the change_column_attrs() call that handles index
drops.

change_column_type() now processes db_index/unique changes from
new_attrs when change_column_type_sets_attrs is True, emitting
index drops as pre-SQL (before the MODIFY) and index adds as post-SQL
(after). The SQLite3 backend also calls the new helper to keep in-memory
database state in sync.

Testing Done


Ran unit tests without the fix and verified that the new tests failed with

  the same issue I saw in the wild.
Ran unit tests with the fix and verified that it was now fixed.
Ran dbtests for mysql, sqlite, and postgresql.

Commits

Summary	ID
Fix ChangeField failure with index+column type changes on MySQL. When a `ChangeField` mutation changes both the field type and `unique`/`db_index` attributes, MySQL's `MODIFY COLUMN` runs before the index is dropped. MySQL rejects this for `TEXT` or `BLOB` columns with the error "BLOB/TEXT column used in key specification without a key length". This happened because `ChangeField.mutate()` returns early after `change_column_type()` when `change_column_type_sets_attrs` is `True` (MySQL), skipping the `change_column_attrs()` call that handles index drops. `change_column_type()` now processes `db_index`/`unique` changes from `new_attrs` when `change_column_type_sets_attrs` is `True`, emitting index drops as pre-SQL (before the `MODIFY`) and index adds as post-SQL (after). The SQLite3 backend also calls the new helper to keep in-memory database state in sync. Testing Done: - Ran unit tests without the fix and verified that the new tests failed with the same issue I saw in the wild. - Ran unit tests with the fix and verified that it was now fixed. - Ran dbtests for mysql, sqlite, and postgresql.	qnonyqrrwwqqowzwqpqlwpvvslzxpvum

Summary

Fix ChangeField failure with index+column type changes on MySQL.

When a `ChangeField` mutation changes both the field type and `unique`/`db_index` attributes, MySQL's `MODIFY COLUMN` runs before the index is dropped. MySQL rejects this for `TEXT` or `BLOB` columns with the error "BLOB/TEXT column used in key specification without a key length". This happened because `ChangeField.mutate()` returns early after `change_column_type()` when `change_column_type_sets_attrs` is `True` (MySQL), skipping the `change_column_attrs()` call that handles index drops. `change_column_type()` now processes `db_index`/`unique` changes from `new_attrs` when `change_column_type_sets_attrs` is `True`, emitting index drops as pre-SQL (before the `MODIFY`) and index adds as post-SQL (after). The SQLite3 backend also calls the new helper to keep in-memory database state in sync. Testing Done: - Ran unit tests without the fix and verified that the new tests failed with the same issue I saw in the wild. - Ran unit tests with the fix and verified that it was now fixed. - Ran dbtests for mysql, sqlite, and postgresql.

qnonyqrrwwqqowzwqpqlwpvvslzxpvum

Issues

Description	From	Last Updated
continuation line over-indented for visual indent Column: 48 Error code: E127	reviewbot	March 17, 2026, 4:45 p.m.

flake8 failed.

JSHint passed.

flake8

django_evolution/db/common.py (Diff revision 1)
The issue has been dropped. Show all issues
```
continuation line over-indented for visual indent

Column: 48
Error code: E127
```

Commits:

	Summary	ID
	Fix ChangeField failure with index+column type changes on MySQL. When a `ChangeField` mutation changes both the field type and `unique`/`db_index` attributes, MySQL's `MODIFY COLUMN` runs before the index is dropped. MySQL rejects this for `TEXT` or `BLOB` columns with the error "BLOB/TEXT column used in key specification without a key length". This happened because `ChangeField.mutate()` returns early after `change_column_type()` when `change_column_type_sets_attrs` is `True` (MySQL), skipping the `change_column_attrs()` call that handles index drops. `change_column_type()` now processes `db_index`/`unique` changes from `new_attrs` when `change_column_type_sets_attrs` is `True`, emitting index drops as pre-SQL (before the `MODIFY`) and index adds as post-SQL (after). The SQLite3 backend also calls the new helper to keep in-memory database state in sync. Testing Done: - Ran unit tests without the fix and verified that the new tests failed with the same issue I saw in the wild. - Ran unit tests with the fix and verified that it was now fixed. - Ran dbtests for mysql, sqlite, and postgresql.	qnonyqrrwwqqowzwqpqlwpvvslzxpvum
	Fix ChangeField failure with index+column type changes on MySQL. When a `ChangeField` mutation changes both the field type and `unique`/`db_index` attributes, MySQL's `MODIFY COLUMN` runs before the index is dropped. MySQL rejects this for `TEXT` or `BLOB` columns with the error "BLOB/TEXT column used in key specification without a key length". This happened because `ChangeField.mutate()` returns early after `change_column_type()` when `change_column_type_sets_attrs` is `True` (MySQL), skipping the `change_column_attrs()` call that handles index drops. `change_column_type()` now processes `db_index`/`unique` changes from `new_attrs` when `change_column_type_sets_attrs` is `True`, emitting index drops as pre-SQL (before the `MODIFY`) and index adds as post-SQL (after). The SQLite3 backend also calls the new helper to keep in-memory database state in sync. Testing Done: - Ran unit tests without the fix and verified that the new tests failed with the same issue I saw in the wild. - Ran unit tests with the fix and verified that it was now fixed. - Ran dbtests for mysql, sqlite, and postgresql.	qnonyqrrwwqqowzwqpqlwpvvslzxpvum

Diff:

Revision 2 (+712)

Show changes

	django_evolution/db/common.py
	django_evolution/db/sqlite3.py
	django_evolution/tests/test_change_field.py
	django_evolution/tests/db/mysql.py
	django_evolution/tests/db/postgresql.py
	django_evolution/tests/db/sqlite3.py

Checks run (2 succeeded)

flake8 passed.

JSHint passed.