+ } elseif (null === $lower && null !== $upper) {
+ // only lower value is defined: query all entries with reading LOWER THAN this value
+ $expression = $filterQuery->getExpr()->lte($field, $max);
+ } elseif (null !== $lower && null === $upper) {
+ // only upper value is defined: query all entries with reading GREATER THAN this value
+ $expression = $filterQuery->getExpr()->gte($field, $min);
+ } else {
+ // both value are defined, perform a between
+ $expression = $filterQuery->getExpr()->between($field, $min, $max);