Switch between new parquet reader and old one

[Damien Profeta]

Hi,

I was looking at the code that read the parquet file and noticed there 
is a switch 'isComplex' to choose if it is possible to use the new 
reader or if we have to use the old one.
The switch is based on the columns of the files (complex type or 
repetition level) but it doesn't care about the columns that have to 
effectively read.

If for the ongoing query, we only read simple column and not with 
repetition level, couldn't we use the new reader? That would be a minor 
optimization but it could be worth.

Thanks
Damien