On 03.02.25 13:19, Alvaro Herrera wrote:
On 2025-Feb-03, Ashutosh Bapat wrote:``` If the constraint is <literal>NOT ENFORCED</literal>, the database system will not check the constraint. It is then up to the application code to ensure that the constraints are satisfied. The database system might still assume that the data actually satisfies the constraint for optimization decisions where this does not affect the correctness of the result. ```IMO the third sentence should be removed because it is bogus. There's no situation in which a not-enforced constraint can be used for any query optimizations -- you cannot know if a constraint remains valid after it's been turned NOT ENFORCED, because anyone could insert data that violates it milliseconds after it stops being enforced. I think the expectation that the application is going to correctly enforce the constraint after it's told the database server not to enforce it, is going to be problematic. As I recall, we already do this in FDWs for instance and it's already a problem.
The database system could use the presence of a not enforced constraint for selectivity estimation, for example.
