**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 :)

for (const auto & command : commands)
    {
        if (command.type == PartitionCommand::DROP_DETACHED_PARTITION
            && !settings.allow_drop_detached)
            throw DB::Exception("Cannot execute query: DROP DETACHED PART is disabled "
                                "(see allow_drop_detached setting)", ErrorCodes::SUPPORT_IS_DISABLED);
        if (command.partition && command.type != PartitionCommand::DROP_DETACHED_PARTITION)
        {
            if (command.part)
            {
                auto part_name = command.partition->as<ASTLiteral &>().value.safeGet<String>();
                
                MergeTreePartInfo::fromPartName(part_name, format_version);
            }
            else
            {
                
                const auto * partition_ast = command.partition->as<ASTPartition>();
                if (partition_ast && partition_ast->all)
                {
                    if (command.type != PartitionCommand::DROP_PARTITION)
                        throw DB::Exception("Only support DETACH PARTITION ALL currently", ErrorCodes::SUPPORT_IS_DISABLED);
                }
                else
                    getPartitionIDFromQuery(command.partition, getContext());
            }
        }
    }
}
void MergeTreeData::checkPartitionCanBeDropped(const ASTPtr & partition, ContextPtr local_context)