**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 :)

extern const int DIRECTORY_ALREADY_EXISTS;
    extern const int TOO_MANY_UNEXPECTED_DATA_PARTS;
    extern const int DUPLICATE_DATA_PART;
    extern const int NO_SUCH_COLUMN_IN_TABLE;
    extern const int LOGICAL_ERROR;
    extern const int ILLEGAL_COLUMN;
    extern const int ILLEGAL_TYPE_OF_COLUMN_FOR_FILTER;
    extern const int CORRUPTED_DATA;
    extern const int BAD_TYPE_OF_FIELD;
    extern const int BAD_ARGUMENTS;
    extern const int INVALID_PARTITION_VALUE;
    extern const int METADATA_MISMATCH;
    extern const int PART_IS_TEMPORARILY_LOCKED;
    extern const int TOO_MANY_PARTS;
    extern const int INCOMPATIBLE_COLUMNS;
    extern const int BAD_TTL_EXPRESSION;
    extern const int INCORRECT_FILE_NAME;
    extern const int BAD_DATA_PART_NAME;
    extern const int READONLY_SETTING;
    extern const int ABORTED;
    extern const int UNKNOWN_PART_TYPE;
    extern const int UNKNOWN_DISK;
    extern const int NOT_ENOUGH_SPACE;
    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
    extern const int SUPPORT_IS_DISABLED;
    extern const int TOO_MANY_SIMULTANEOUS_QUERIES;
    extern const int INCORRECT_QUERY;
    extern const int CANNOT_RESTORE_TABLE;
}
static void checkSampleExpression(const StorageInMemoryMetadata & metadata, bool allow_sampling_expression_not_in_primary_key, bool check_sample_column_is_correct)