Request for Implementation of Custom Error Messages for CHECK Constraints

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,