I have ClickHouse server running in virtual environment that reports the following warning:

```
# clickhouse-client
ClickHouse client version 22.7.2.15 (official build).
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 22.7.2 revision 54457.

Warnings:
 * Linux is not using a fast TSC clock source. Performance can be degraded. Check /sys/devices/system/clocksource/clocksource0/current_clocksource

# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
kvm-clock
```

It looks like a false positive as kvm-clock is considered a preferable clock source for kvm-based VMs.
https://opensource.com/article/17/6/timekeeping-linux-vms

Regardless of whether it's a bug or not, I'd like to have some mechanism that allows to disable particular warnings. There are may be other questionable warnings in the future.

{
    auto it = special_scalars.find(name);
    if (special_scalars.end() == it)
        return nullptr;
    return &it->second;
}
Tables Context::getExternalTables() const
{
    if (isGlobalContext())
        throw Exception(ErrorCodes::LOGICAL_ERROR, "Global context cannot have external tables");
    auto lock = getLock();
    Tables res;
    for (const auto & table : external_tables_mapping)
        res[table.first] = table.second->getTable();
    auto query_context_ptr = query_context.lock();
    auto session_context_ptr = session_context.lock();
    if (query_context_ptr && query_context_ptr.get() != this)
    {
        Tables buf = query_context_ptr->getExternalTables();
        res.insert(buf.begin(), buf.end());
    }
    else if (session_context_ptr && session_context_ptr.get() != this)
    {
        Tables buf = session_context_ptr->getExternalTables();
        res.insert(buf.begin(), buf.end());
    }
    return res;
}
void Context::addExternalTable(const String & table_name, TemporaryTableHolder && temporary_table)