Got division by zero errors from a proficiency query in Oli.Delivery.Metrics.proficiency_per_student_across/2 . Such an error prevents display of the Students page, and probably other displays showing proficiencies.
This PR adds NULLIF guards around proficiency calculation denominators using ResourceSummary.num_first_attempts to prevent possible division by zero.
The source of the error is not understood. The queries evidently were written on the assumption they will never get a 0 valued sum of num_first_attempts (though might get null). The error suggests some resource is unexpectedly causing an explicit 0 to be recorded in num_first_attempts in the resource summary table, rather than leaving it null.
The error was observed in a somewhat unusual situation: a client-side evaluated activity, the LogicLab, which asynchronously resets part attempts and submits activity evaluations, in context of a containing graded page that was never itself submitted, with this being done by a unique guest student who can never return to complete it.
But since this can happen in the system, should protect against it. Change should be harmless.
Got division by zero errors from a proficiency query in
Oli.Delivery.Metrics.proficiency_per_student_across/2. Such an error prevents display of the Students page, and probably other displays showing proficiencies.This PR adds NULLIF guards around proficiency calculation denominators using
ResourceSummary.num_first_attemptsto prevent possible division by zero.The source of the error is not understood. The queries evidently were written on the assumption they will never get a 0 valued sum of
num_first_attempts(though might get null). The error suggests some resource is unexpectedly causing an explicit 0 to be recorded innum_first_attemptsin the resource summary table, rather than leaving it null.The error was observed in a somewhat unusual situation: a client-side evaluated activity, the LogicLab, which asynchronously resets part attempts and submits activity evaluations, in context of a containing graded page that was never itself submitted, with this being done by a unique guest student who can never return to complete it.
But since this can happen in the system, should protect against it. Change should be harmless.