**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 :)

ColumnsDescription object_columns;
    MergeTreePartsMover parts_mover;
    
    
    
    
    
    
    
    
    BackgroundJobsAssignee background_operations_assignee;
    BackgroundJobsAssignee background_moves_assignee;
    bool use_metadata_cache;
    
    
    
    IExecutableTask::TaskResultCallback common_assignee_trigger;
    IExecutableTask::TaskResultCallback moves_assignee_trigger;
    using DataPartIteratorByInfo = DataPartsIndexes::index<TagByInfo>::type::iterator;
    using DataPartIteratorByStateAndInfo = DataPartsIndexes::index<TagByStateAndInfo>::type::iterator;
    boost::iterator_range<DataPartIteratorByStateAndInfo> getDataPartsStateRange(DataPartState state) const
    {
        auto begin = data_parts_by_state_and_info.lower_bound(state, LessStateDataPart());
        auto end = data_parts_by_state_and_info.upper_bound(state, LessStateDataPart());
        return {begin, end};
    }
    boost::iterator_range<DataPartIteratorByInfo> getDataPartsPartitionRange(const String & partition_id) const