**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 getTotalMergesWithTTLInMergeList() const;
    using WriteAheadLogPtr = std::shared_ptr<MergeTreeWriteAheadLog>;
    WriteAheadLogPtr getWriteAheadLog();
    MergeTreeDataFormatVersion format_version;
    
    const MergingParams merging_params;
    bool is_custom_partitioned = false;
    
    Int64 minmax_idx_date_column_pos = -1; 
    Int64 minmax_idx_time_column_pos = -1; 
    
    static ExpressionActionsPtr getMinMaxExpr(const KeyDescription & partition_key, const ExpressionActionsSettings & settings);
    
    static Names getMinMaxColumnsNames(const KeyDescription & partition_key);
    
    static DataTypes getMinMaxColumnsTypes(const KeyDescription & partition_key);
    ExpressionActionsPtr getPrimaryKeyAndSkipIndicesExpression(const StorageMetadataPtr & metadata_snapshot) const;
    ExpressionActionsPtr getSortingKeyAndSkipIndicesExpression(const StorageMetadataPtr & metadata_snapshot) const;
    
    
    CompressionCodecPtr getCompressionCodecForPart(size_t part_size_compressed, const IMergeTreeDataPart::TTLInfos & ttl_infos, time_t current_time) const;
    std::lock_guard<std::mutex> getQueryIdSetLock() const { return std::lock_guard<std::mutex>(query_id_set_mutex); }
    
    
    bool insertQueryIdOrThrow(const String & query_id, size_t max_queries) const;
    bool insertQueryIdOrThrowNoLock(const String & query_id, size_t max_queries) const TSA_REQUIRES(query_id_set_mutex);
    
    void removeQueryId(const String & query_id) const;
    void removeQueryIdNoLock(const String & query_id) const TSA_REQUIRES(query_id_set_mutex);