https://clickhouse-test-reports.s3.yandex.net/8367/333ec2e496f4fe4addd22d5fa7c5c2a499099c57/fuzzer/fuzzer.log#fail1
else if (dict_struct.key)
    {
        auto first = true;
        for (const auto & key : *dict_struct.key)
        {
            if (!first)
                writeString(", ", out);
            first = false;
            if (!key.expression.empty())
            {
                writeParenthesisedString(key.expression, out);
                writeString(" AS ", out);
            }
            writeQuoted(key.name, out);
        }
    }
    for (const auto & attr : dict_struct.attributes)
    {
        writeString(", ", out);
        if (!attr.expression.empty())
        {
            writeParenthesisedString(attr.expression, out);
            writeString(" AS ", out);
        }
        writeQuoted(attr.name, out);
    }
    writeString(" FROM ", out);
    if (!db.empty())
    {
        writeQuoted(db, out);