**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 :)

Row partition_row(fields_count);
    if (fields_count == 0)
    {
        /
        assert(!partition_ast.fields_count);
        assert(typeid_cast<ASTFunction *>(partition_ast.value.get()));
        assert(partition_ast.value->as<ASTFunction>()->name == "tuple");
        assert(partition_ast.value->as<ASTFunction>()->arguments);
        auto args = partition_ast.value->as<ASTFunction>()->arguments;
        if (!args)
            throw Exception(ErrorCodes::BAD_ARGUMENTS, "Expected at least one argument in partition AST");
        bool empty_tuple = partition_ast.value->as<ASTFunction>()->arguments->children.empty();
        if (!empty_tuple)
            throw Exception(ErrorCodes::INVALID_PARTITION_VALUE, "Partition key is empty, expected 'tuple()' as partition key");
    }
    else if (fields_count == 1)
    {
        ASTPtr partition_value_ast = partition_ast.value;
        if (auto * tuple = partition_value_ast->as<ASTFunction>())
        {
            assert(tuple->name == "tuple");
            assert(tuple->arguments);
            assert(tuple->arguments->children.size() == 1);
            partition_value_ast = tuple->arguments->children[0];
        }
        /
        Field partition_key_value = evaluateConstantExpression(partition_value_ast, local_context).first;
        partition_row[0] = convertFieldToTypeOrThrow(partition_key_value, *key_sample_block.getByPosition(0).type);
    }
    else