**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 :)

insert(max_column, range.right);
            }
        }
        ++pos;
    }
    if (!primary_key_max_column_name.empty())
    {
        if (required_columns_set.contains(partition_minmax_count_column_names[pos]))
        {
            for (const auto & part : real_parts)
            {
                const auto & primary_key_column = *part->index[0];
                auto & min_column = assert_cast<ColumnAggregateFunction &>(*partition_minmax_count_columns[pos]);
                insert(min_column, primary_key_column[0]);
            }
        }
        ++pos;
        if (required_columns_set.contains(partition_minmax_count_column_names[pos]))
        {
            for (const auto & part : real_parts)
            {
                const auto & primary_key_column = *part->index[0];
                auto & max_column = assert_cast<ColumnAggregateFunction &>(*partition_minmax_count_columns[pos]);
                insert(max_column, primary_key_column[primary_key_column.size() - 1]);
            }
        }
        ++pos;
    }
    bool has_count
        = std::any_of(required_columns.begin(), required_columns.end(), [&](const auto & name) { return startsWith(name, "count"); });