write readme and example

[ratal]

Hi, The documentation describes well what can be done for reading. However, I am writing a crate to convert specific measurement file into parquet format ; There is no explanation on how to write a parquet file. I could find in the tests an implementation example but it is limited for my case. I do not know what should be most suitable parallelization for instance considering I already have data in column form in memory. I suppose documentation is not yet mature as parquet2 is still in active development and main usage of this crate is reading but it would help with more explanation.

[TurnOfACard]

Hi ratal, The arrow2 crate has a good example if you use arrow2?

[ratal]

Thanks, I could succeed to write a first proto link I had to remove statistics, difficult with dyn traits to input max and min values. I am trying to put the loop for each column in parallel with rayon but FileWriter seems to need an Arc<Mutex> Anyway thank again for pointing to documentation, you can keep opened the issue as reminder or close it. If I still have issues I open new ticket specifically.

[jorgecarleitao]

Cool!

For rayon, we have an example here: https://github.com/jorgecarleitao/arrow2/blob/main/examples/parquet_write_parallel/src/main.rs#L45

We currently only support an iterator (not a parallel iterator) of columns, which is why the columns must be pre-serialized before writing.