**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 auto & projections = part->getProjectionParts();
        auto it = projections.find(candidate.desc->name);
        if (it != projections.end())
            projection_parts.push_back(it->second);
        else
            normal_parts.push_back(part);
    }
    if (projection_parts.empty())
        return;
    auto projection_result_ptr = reader.estimateNumMarksToRead(
        projection_parts,
        candidate.required_columns,
        storage_snapshot->metadata,
        candidate.desc->metadata,
        query_info,
        added_filter_nodes,
        query_context,
        settings.max_threads,
        max_added_blocks);
    if (projection_result_ptr->error())
        return;
    auto sum_marks = projection_result_ptr->marks();
    if (normal_parts.empty())
    {
        /
        /
        candidate.complete = true;
    }
    else