hi, I have a big csv, is it possible to read lazily the lines in inverse order? from tail to head

You can reverse the file with tac file.csv > rev_file.csv and then read rev_file.csv normally. Definitely an option if the file isn't too large.

surely someone has made a "from end buffered line reader" on top of mmap

it's inefficient (requires consuming the whole thing and working backward) but doable

I'm curious why that would be useful. @vachichng

I assume you have something accumulated in time order and you want to process from new to old

next question is if anybody hooked that up to read lines in backward order yet

clever usage of tac and ProcessBuilder with output to an iostream instead of file might allow similar via the OS(?)

@drewverlee exactly as Alex said, I have a big cvs of timestamped data that I have to process it windowed by timeframe and the original source has it ordered by recent to old, but the window function needs old to recent

maybe ReversedLinesFileReader would work, http://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/input/ReversedLinesFileReader.html

> Reads lines in a file reversely (similar to a BufferedReader, but starting at the last line). Useful for e.g. searching in log files.

nice, I'd hoped someone made that

But if you have to process the whole thing then the out put will be the same no? The window closing logic should handle any order of time stamped events.

many reducing processes aren't associative, ordering can matter a lot

Yes, but I think, for instance, onyxs semantics express the window closing trigger this way.

@drewverlee no, ordering matters because the window function needs to know the oldest timestamp to create sequence

hello again everyone! i have a question: is there a preferred structure in a repo for having both a client (cljs) and api (clj)?