Avoiding Pitfalls with Enum Indexing #

1. Not Indexing Low-Cardinality Enums #

If an enum column has very few values (true/false, small/medium/large), indexing may not help much. The database engine can scan small tables quickly without an index.

2. Ignoring Write Performance Issues #

Every time you insert or update a record, the database must update the index. If your table has frequent writes, indexing an enum column may slow down inserts.

3. Forgetting to Rebuild Indexes After Enum Changes #

If you change an enum mapping, existing index values might become invalid. After modifying enums, always rebuild indexes:

rails db:migrate:redo

Or manually reindex:

REINDEX TABLE users;