streem | prototype of stream based programming language | Functional Programming library

From Spark documentation, the suggested way:

count() - Cannot return a single count from a streaming Dataset. Instead, use ds.groupBy().count() which returns a streaming Dataset containing a running count.

Note that, you should use complete mode.

you can check the first column before performing all of those code by

The answer is different for different streams .

The stringstream has a memory buffer and an indicator that remembers where you were up to on the reading. So the next read starts where the previous read left off.

File streams work in a similar way, they remember which point of the file they are up to. In both cases you can change position (including resetting to the beginning) using seekg.

File streams don't have separate read and write positions, so this same code might behave differently for a file stream . (In fact I think it causes undefined behaviour to read and write without an intervening seek).

Other input streams might not have seekable buffers, e.g. cin .