**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 :)

size_t getTotalActiveSizeInBytes() const;
    size_t getTotalActiveSizeInRows() const;
    size_t getPartsCount() const;
    size_t getMaxPartsCountForPartitionWithState(DataPartState state) const;
    size_t getMaxPartsCountForPartition() const;
    size_t getMaxInactivePartsCountForPartition() const;
    
    
    std::optional<Int64> getMinPartDataVersion() const;
    
    DetachedPartsInfo getDetachedParts() const;
    static void validateDetachedPartName(const String & name);
    void dropDetached(const ASTPtr & partition, bool part, ContextPtr context);
    MutableDataPartsVector tryLoadPartsToAttach(const ASTPtr & partition, bool attach_part,
                                                ContextPtr context, PartsTemporaryRename & renamed_parts);
    
    
    void delayInsertOrThrowIfNeeded(Poco::Event * until, ContextPtr query_context) const;
    
    
    
    
    bool renameTempPartAndAdd(
        MutableDataPartPtr & part,
        Transaction & transaction,
        DataPartStorageBuilderPtr builder,
        DataPartsLock & lock);