**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 (txn)
        transactions_enabled.store(true);
    auto remove_time = clear_without_timeout ? 0 : time(nullptr);
    bool removed_active_part = false;
    for (const DataPartPtr & part : remove)
    {
        if (part->version.creation_csn != Tx::RolledBackCSN)
            MergeTreeTransaction::removeOldPart(shared_from_this(), part, txn);
        if (part->getState() == MergeTreeDataPartState::Active)
        {
            removePartContributionToColumnAndSecondaryIndexSizes(part);
            removePartContributionToDataVolume(part);
            removed_active_part = true;
        }
        if (part->getState() == MergeTreeDataPartState::Active || clear_without_timeout)
            part->remove_time.store(remove_time, std::memory_order_relaxed);
        if (part->getState() != MergeTreeDataPartState::Outdated)
            modifyPartState(part, MergeTreeDataPartState::Outdated);
        if (isInMemoryPart(part) && getSettings()->in_memory_parts_enable_wal)
            getWriteAheadLog()->dropPart(part->name);
    }
    if (removed_active_part)
        resetObjectColumnsFromActiveParts(acquired_lock);
}
void MergeTreeData::removePartsFromWorkingSetImmediatelyAndSetTemporaryState(const DataPartsVector & remove)