Do less copying/passes through the data

[andrewgross]

This will never be perfect in python, but right now its pretty disgusting what we do when we load JSON and convert it to a columnar format.

[sojovi]

You are reading twice the json file (here _convert_data_without_schema and here _convert_data_with_column_names) only in the case the user didnt provide any schema.

I would like to work on this, I think both functions could be merged in a single function that extracts the column names and at the same time assigns the values to the corresponding column.

[andrewgross]

That would be great! There should be good test coverage for the results from those functions. I definitely wrote some inefficient code here to get it working, and did not return to improve it. Feel free to open a PR!

[sojovi]

Merged both functions in a single one, now is reading and converting the whole JSON in a single loop (I dont excel as Python dev but I think is a decent improvement). Regarding tests, I'll work with a different version of JSON file (more complex, columns, etc) and see how it works. I would like to benchmark the new version with the previous version but not a priority I think by now.