**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 :)

continue;
                }
                /
                if (minmax_count_projection && dynamic_cast<const AggregateFunctionCount *>(aggregate.function.get()))
                {
                    const auto * count_column = sample_block.findByName("count()");
                    if (!count_column)
                        throw Exception(
                            ErrorCodes::LOGICAL_ERROR, "`count()` column is missing when minmax_count_projection == true. It is a bug");
                    aggregates.insert({count_column->column, count_column->type, aggregate.column_name});
                    continue;
                }
                /
                return;
            }
            /
            /
            /
            /
            candidate.before_aggregation = analysis_result.before_aggregation->clone();
            auto required_columns = candidate.before_aggregation->foldActionsByProjection(keys, sample_block_for_keys);
            /
            if (required_columns.empty() && (!keys.empty() && !candidate.before_aggregation->getRequiredColumns().empty()))
                return;
            if (analysis_result.optimize_aggregation_in_order)
                attach_aggregation_in_order_info();
            /
            candidate.before_aggregation->reorderAggregationKeysForProjection(key_name_pos_map);
            candidate.before_aggregation->addAggregatesViaProjection(aggregates);
            if (rewrite_before_where(candidate, projection, required_columns, sample_block_for_keys, aggregates))