I use an expression as `update_field` because this feature is not implemented yet: https://github.com/ClickHouse/ClickHouse/issues/6084

20.5 generates an incorrect query in this case:
```WHERE `date_add(updated_date, interval 15 minute)` >= '2020-07-02 16:40:06'```

The exception:
```mysqlxx::BadQuery: Unknown column 'date_add(updated_date, interval 15 minute)' in 'where clause'```

The problem is here: 
https://github.com/ClickHouse/ClickHouse/blob/b81c66a03148afc02647df3c11aec40382329912/src/Dictionaries/ExternalQueryBuilder.cpp#L172
The change was introduced in this PR: https://github.com/ClickHouse/ClickHouse/pull/11079

writeString(")", out);
        }
    }
    else if (method == IN_WITH_TUPLES)
    {
        composeInWithTuples(key_columns, requested_rows, out, 0, key_columns.size());
    }
    else 
    {
        
        
        
        
        
        
        
        composeKeyCondition(key_columns, requested_rows.at(0), out, 0, partition_key_prefix);
        if (partition_key_prefix && partition_key_prefix < key_columns.size())
            writeString(" AND ", out);
        if (partition_key_prefix < key_columns.size())
            composeInWithTuples(key_columns, requested_rows, out, partition_key_prefix, key_columns.size());
    }
    if (!where.empty() && method != CASSANDRA_SEPARATE_PARTITION_KEY)
    {
        writeString(")", out);
    }
    writeString(";", out);
    return out.str();
}
void ExternalQueryBuilder::composeKeyCondition(const Columns & key_columns, const size_t row, WriteBuffer & out,