PostgreSQL Project Leaders,
Currently, when a CHECK constraint is violated, PostgreSQL returns a generic error message that includes the constraint name. While informative for developers familiar with the database schema, this message can be less clear for other team members, end-users, or in application logs. This lack of specificity hinders the quick identification of the exact business rule that has been violated and can lead to more time-consuming debugging and less user-friendly error messages in applications.
Proposal:
I propose extending the syntax of the ALTER TABLE ADD CONSTRAINT statement (and potentially CREATE TABLE) to allow for the specification of a custom error message for each CHECK constraint. A possible syntax could be as follows:
ALTER TABLE table_name
ADD CONSTRAINT constraint_name
CHECK (condition)
MESSAGE 'Custom error message when the condition is not met.';
Benefits of Implementation:
Improved User Experience: Applications could capture and display more contextual and helpful error messages to end-users, improving usability and reducing confusion.
Enhanced Debugging: Developers could immediately identify the specific business rule that has been violated, speeding up the debugging and resolution of data integrity issues.
Implicit Documentation: The custom message would serve as a way to document the intent of the constraint directly within the database schema, facilitating understanding and maintenance of the data model.
Consistency: It would allow for a more consistent approach to providing informative feedback on business rule violations, complementing the existing capability in triggers.
Best regards,
