**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 :)

data_parts_indexes.erase(it_part);
    if (restore_covered && part->info.level == 0)
    {
        LOG_WARNING(log, "Will not recover parts covered by zero-level part {}", part->name);
        return;
    }
    if (restore_covered)
    {
        Strings restored;
        bool error = false;
        String error_parts;
        Int64 pos = part->info.min_block;
        auto is_appropriate_state = [] (DataPartState state)
        {
            return state == DataPartState::Active || state == DataPartState::Outdated;
        };
        auto update_error = [&] (DataPartIteratorByInfo it)
        {
            error = true;
            error_parts += (*it)->getNameWithState() + " ";
        };
        auto activate_part = [this, &restored_active_part](auto it)
        {
            
            
            chassert((*it)->version.isRemovalTIDLocked());
            if ((*it)->version.removal_tid_lock == Tx::PrehistoricTID.getHash())
                (*it)->version.unlockRemovalTID(Tx::PrehistoricTID, TransactionInfoContext{getStorageID(), (*it)->name});
            else
                throw Exception(ErrorCodes::LOGICAL_ERROR, "Cannot activate part {} that was removed by transaction ({})",