**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 :)

const StorageInMemoryMetadata & new_metadata, const StorageInMemoryMetadata & old_metadata, bool attach) const
{
    if (!new_metadata.sorting_key.definition_ast)
        throw Exception("ORDER BY cannot be empty", ErrorCodes::BAD_ARGUMENTS);
    KeyDescription new_sorting_key = new_metadata.sorting_key;
    KeyDescription new_primary_key = new_metadata.primary_key;
    size_t sorting_key_size = new_sorting_key.column_names.size();
    size_t primary_key_size = new_primary_key.column_names.size();
    if (primary_key_size > sorting_key_size)
        throw Exception("Primary key must be a prefix of the sorting key, but its length: "
            + toString(primary_key_size) + " is greater than the sorting key length: " + toString(sorting_key_size),
            ErrorCodes::BAD_ARGUMENTS);
    NameSet primary_key_columns_set;
    for (size_t i = 0; i < sorting_key_size; ++i)
    {
        const String & sorting_key_column = new_sorting_key.column_names[i];
        if (i < primary_key_size)
        {
            const String & pk_column = new_primary_key.column_names[i];
            if (pk_column != sorting_key_column)
                throw Exception("Primary key must be a prefix of the sorting key, but the column in the position "
                    + toString(i) + " is " + sorting_key_column +", not " + pk_column,
                    ErrorCodes::BAD_ARGUMENTS);
            if (!primary_key_columns_set.emplace(pk_column).second)
                throw Exception("Primary key contains duplicate columns", ErrorCodes::BAD_ARGUMENTS);
        }
    }
    auto all_columns = new_metadata.columns.getAllPhysical();