**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 :)

{
    disk->removeRecursive(path);
    return false;
}
PartitionCommandsResultInfo MergeTreeData::unfreezePartitionsByMatcher(MatcherFn matcher, const String & backup_name, ContextPtr local_context)
{
    auto backup_path = fs::path("shadow") / escapeForFileName(backup_name) / relative_data_path;
    LOG_DEBUG(log, "Unfreezing parts by path {}", backup_path.generic_string());
    auto disks = getStoragePolicy()->getDisks();
    return Unfreezer().unfreezePartitionsFromTableDirectory(matcher, backup_name, disks, backup_path, local_context);
}
bool MergeTreeData::canReplacePartition(const DataPartPtr & src_part) const
{
    const auto settings = getSettings();
    if (!settings->enable_mixed_granularity_parts || settings->index_granularity_bytes == 0)
    {
        if (!canUseAdaptiveGranularity() && src_part->index_granularity_info.is_adaptive)
            return false;
        if (canUseAdaptiveGranularity() && !src_part->index_granularity_info.is_adaptive)
            return false;
    }
    return true;
}
void MergeTreeData::writePartLog(