Reading the first N rows

[iscalprog]

Sometimes it is useful to read just the first N rows, before reading everything. Is there a recommend way to achieve this?

[davidanthoff]

I actually would have thought that the nrows argument would control that, but apparently it doesn't.

Having the ability to only return n rows would be really, really useful. I think the API for that should just be that nrows controls that.

[jpsamaroo]

I'd like this feature to support JuliaData/JuliaDB.jl#288, where we want to parse only the header, and then pass the header to workers who will then parse the rest of the file in chunks.

[davidanthoff]

#145 was the first step: it freed the name nrows for this. Next step is to add the actual functionality.

I was actually also thinking to breaking out a separate function that just gets you the header, so that one doesn't have to use nrows=0 to do that. I also have a use case for that (a purely streaming mode that doesn't allocate any result vectors inside TextParse.jl). Just wondering whether that would also be useful for what you are working on?

[jpsamaroo]

The separate header-parsing function would be super useful, and would allow me to finish the current PR I'm working on!

A streaming interface would be interesting, although I'm not yet sure what I'd use it for 😄

[davidanthoff]

Ok, cool. No promise on timing, but I'll try to give it a bit more priority than it has right now ;)