**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 :)

{
    Strings res;
    auto disks = getStoragePolicy()->getDisks();
    for (const auto & disk : disks)
        res.push_back(getFullPathOnDisk(disk));
    return res;
}
void MergeTreeData::reportBrokenPart(MergeTreeData::DataPartPtr & data_part) const
{
    if (data_part->data_part_storage && data_part->data_part_storage->isBroken())
    {
        auto parts = getDataPartsForInternalUsage();
        LOG_WARNING(log, "Scanning parts to recover on broken disk {}@{}.", data_part->data_part_storage->getDiskName(), data_part->data_part_storage->getDiskPath());
        for (const auto & part : parts)
        {
            if (part->data_part_storage && part->data_part_storage->getDiskName() == data_part->data_part_storage->getDiskName())
                broken_part_callback(part->name);
        }
    }
    else if (data_part && data_part->getState() == MergeTreeDataPartState::Active)
        broken_part_callback(data_part->name);
    else
        LOG_DEBUG(log, "Will not check potentially broken part {} because it's not active", data_part->getNameWithState());
}
MergeTreeData::MatcherFn MergeTreeData::getPartitionMatcher(const ASTPtr & partition_ast, ContextPtr local_context) const