presto-main/src/main/java/io/prestosql/operator/scalar/JsonOperators.java/JsonOperators/castFromBigint
class JsonOperators:    @ScalarOperator(CAST)
    @SqlType(JSON)
    public static Slice castFromBigint(@SqlType(BIGINT) long value)
    {
        return internalCastFromLong(value, 20);
    }