You can define a database index in your data model to enforce uniqueness of table attributes across multiple rows or to make searches quicker using those attributes as filters. In OutSystems, you can model a database index in the entity element.
To create an index for an entity:
- Open the entity by double-clicking on it or selecting the Indexes property.
- Go to the Indexes tab and create a new index.
- Add the attributes you want to include in the index.
- If you want to have unique values for the selected attributes, set the Unique property to
- To apply the index created in the database, publish the application.
In the GoOutWeb application, an application to find and review interesting places, we want to ensure that an end user cannot give more than one review to a place in the same day.
To create a unique index in the Review entity to ensure this restriction:
Open the Review entity.
In the Indexes tab, add a new index and name it
Add the attributes: PlaceId, UserId, and Date. This will ensure that the same value for these attributes cannot be repeated in other records of Review table.
Set the index to unique.
Publish the module. While publishing, OutSystems creates the index in the database.
From now on, when an end user tries to save the second review for the same place in the same day, OutSystems raises a database exception.