duplicated value when merging grades

[Jordi Pujol-Ahulló]

I detected some notice from Moodle for duplicated value like this just today:

Did you remember to make the first column something unique in your call to get_records? Duplicate value '1318' found in column 'authorid'.

    line 1292 of /lib/dml/mysqli_native_moodle_database.php: call to debugging()
    line 1159 of /mod/workshop/lib.php: call to mysqli_native_moodle_database->get_records_sql()
    line 1403 of /lib/gradelib.php: call to workshop_update_grades()
    line 472 of /admin/tool/mergeusers/lib/mergeusertool.php: call to grade_update_mod_grades()
    line 271 of /admin/tool/mergeusers/lib/mergeusertool.php: call to MergeUserTool->updateGrades()
    line 192 of /admin/tool/mergeusers/lib/mergeusertool.php: call to MergeUserTool->_merge()
    line 135 of /admin/tool/mergeusers/index.php: call to MergeUserTool->merge()

I record it here for addressing it in the future. I do not know if this is a real problem or it is not.

Jordi