func newSargNotMissing(expr *expression.IsNotMissing) *sargNotMissing { rv := &sargNotMissing{} rv.sarg = func(expr2 expression.Expression) (Spans, error) { if expr.EquivalentTo(expr2) { return _SELF_SPANS, nil } if !expr.Operand().EquivalentTo(expr2) { return nil, nil } return _FULL_SPANS, nil } return rv }