**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 :)

{
    auto lock = lockParts();
    for (const auto & part : parts)
    {
        
        part->assertState({DataPartState::Deleting});
        modifyPartState(part, DataPartState::Outdated);
    }
}
void MergeTreeData::removePartsFinally(const MergeTreeData::DataPartsVector & parts)
{
    {
        auto lock = lockParts();
        
        for (const auto & part : parts)
        {
            
            if (part->getState() == DataPartState::Temporary)
                continue;
            auto it = data_parts_by_info.find(part->info);
            if (it == data_parts_by_info.end())