**Describe the bug**

Since we upgraded to 20.10.3.30, one of our clickhouse cluster takes much more time to start. (Up to 50 minutes, and before it took ~3 minutes)
The log file is filled with
>  <Debug> DiskLocal: Reserving 1.00 MiB on disk `default`, having unreserved 16.90 TiB

Additionally, the memory consumption increases, linearly, a lot (up to arround 230 G for us) and then drop back to normal values once clickhouse finished starting up. During that loading phase, a single CPU core is used at 100%.
If that memory is not available for the machine, clickhouse gets OOMed by the kernel.


**How to reproduce**
* Issue appeared after we upgraded to ClickHouse server version 20.10.3.30

* How could I find wich of our tables may be responsible for that ?


**Expected behavior**
A fast startup :)

{
    if (!canUseAdaptiveGranularity())
    {
        if (out_reason && (settings.min_rows_for_wide_part != 0 || settings.min_bytes_for_wide_part != 0
            || settings.min_rows_for_compact_part != 0 || settings.min_bytes_for_compact_part != 0))
        {
            *out_reason = fmt::format(
                    "Table can't create parts with adaptive granularity, but settings"
                    " min_rows_for_wide_part = {}"
                    ", min_bytes_for_wide_part = {}"
                    ", min_rows_for_compact_part = {}"
                    ", min_bytes_for_compact_part = {}"
                    ". Parts with non-adaptive granularity can be stored only in Wide (default) format.",
                    settings.min_rows_for_wide_part,    settings.min_bytes_for_wide_part,
                    settings.min_rows_for_compact_part, settings.min_bytes_for_compact_part);
        }
        return false;
    }
    return true;
}
MergeTreeData::AlterConversions MergeTreeData::getAlterConversionsForPart(const MergeTreeDataPartPtr part) const