The index tables must always be re-ordered/updated upon creating or changing an attribute that affects the index. Also, the database optimizer needs to pick the right index for a query, so multiple indices increase the chance the optimizer chooses the wrong one.
When set to 3 for example, this rule finds all entities with more than 3 indices and makes it easy to review if the indices are distinctive and useful.
Please note that, there is no maximum number of indices advised. It all depends on the amount of mutations to the entity and the available disk space.
Noncompliant example:
Additional resources on indices
- Mendix documentation: Implement Community Best Practices for App Performance – Studio Pro 9 How-to’s | Mendix Documentation.
- A recommended read is this great blog by Martin Leppen, Mendix MVP at Cape Group: Performance modeling in Mendix — Indexes | by Martin Leppen | Mendix Community | Feb, 2022 | Medium. Explaining everything you should know around indices.