presto-main/src/main/java/io/prestosql/sql/planner/ExpressionInterpreter.java/ExpressionInterpreter/visitNotExpression
class ExpressionInterpreter:        @Override
        protected Object visitNotExpression(NotExpression node, Object context)
        {
            Object value = process(node.getValue(), context);
            if (value == null) {
                return null;
            }

            if (value instanceof Expression) {
                return new NotExpression(toExpression(value, type(node.getValue())));
            }

            return !(Boolean) value;
        }