**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 it = data_parts_by_info.find(part->info);
        if (it == data_parts_by_info.end() || (*it).get() != part.get())
            throw Exception("Part " + part->name + " doesn't exist", ErrorCodes::LOGICAL_ERROR);
        if (!data_parts_by_state_and_info.modify(data_parts_indexes.project<TagByStateAndInfo>(it), getStateModifier(state)))
            throw Exception("Can't modify " + (*it)->getNameWithState(), ErrorCodes::LOGICAL_ERROR);
    }
    
    std::mutex grab_old_parts_mutex;
    
    std::mutex clear_old_temporary_directories_mutex;
    void checkProperties(const StorageInMemoryMetadata & new_metadata, const StorageInMemoryMetadata & old_metadata, bool attach = false) const;
    void setProperties(const StorageInMemoryMetadata & new_metadata, const StorageInMemoryMetadata & old_metadata, bool attach = false);
    void checkPartitionKeyAndInitMinMax(const KeyDescription & new_partition_key);
    void checkTTLExpressions(const StorageInMemoryMetadata & new_metadata, const StorageInMemoryMetadata & old_metadata) const;
    void checkStoragePolicy(const StoragePolicyPtr & new_storage_policy) const;
    
    void calculateColumnAndSecondaryIndexSizesImpl();
    
    void addPartContributionToColumnAndSecondaryIndexSizes(const DataPartPtr & part);
    void removePartContributionToColumnAndSecondaryIndexSizes(const DataPartPtr & part);
    
    DataPartPtr getAnyPartInPartition(const String & partition_id, DataPartsLock & data_parts_lock) const;
    
    
    DataPartsVector getActivePartsToReplace(
        const MergeTreePartInfo & new_part_info,
        const String & new_part_name,