Testing data
```
select 'aaaaaaaa,bbbbbbbb,cccccccc,dddddddd,eeeeeeee,ffffffff,gggg,hhh' from numbers(3000000) into outfile '/tmp/test.csv'
```
Testing command
```
echo "select count() from file('/tmp/test.csv', CSV, 'a String, b String, c String, d String, e String, f String, g String, h String') where not ignore(e)" | clickhouse-benchmark
```
Before
```
QPS: 1.317, RPS: 3949749.687, MiB/s: 478.380, result RPS: 1.317, result MiB/s: 0.000.
0.000% 0.704 sec.
10.000% 0.712 sec.
20.000% 0.718 sec.
30.000% 0.726 sec.
40.000% 0.739 sec.
50.000% 0.754 sec.
60.000% 0.770 sec.
70.000% 0.788 sec.
80.000% 0.798 sec.
90.000% 0.815 sec.
95.000% 0.826 sec.
99.000% 0.850 sec.
99.900% 0.857 sec.
99.990% 0.858 sec.
```
After
```
QPS: 1.533, RPS: 4598308.336, MiB/s: 556.932, result RPS: 1.533, result MiB/s: 0.000.
0.000% 0.626 sec.
10.000% 0.635 sec.
20.000% 0.639 sec.
30.000% 0.642 sec.
40.000% 0.643 sec.
50.000% 0.645 sec.
60.000% 0.649 sec.
70.000% 0.652 sec.
80.000% 0.658 sec.
90.000% 0.682 sec.
95.000% 0.710 sec.
99.000% 0.727 sec.
99.900% 0.733 sec.
99.990% 0.734 sec.
```
http://eel.is/c++draft/class.copy.elision#:constructor,copy,elision
Some quote:
> Speaking of RVO, return std::move(w); prohibits it. It means "use move constructor or fail to compile", whereas return w; means "use RVO, and if you can't, use move constructor, and if you can't, use copy constructor, and if you can't, fail to compile."
There is one exception to this rule:
```cpp
Block FilterBlockInputStream::removeFilterIfNeed(Block && block)
{
if (block && remove_filter)
block.erase(static_cast<size_t>(filter_column));
return std::move(block);
}
```
because references are not eligible for NRVO, which is another rule "always move rvalue references and forward universal references" that takes precedence.
