If I use RealTimeSync, will a full comparison start for every modified file?

[Cat]

Let's say I sync lots of folders, maybe almost a full disk minus a few system folders.
I worry that whenever a file gets modified the "FreeFileSync.exe" gets triggered and starts a full comparison that takes ages before it syncs that one file.
In the mean time I may modify another file that may trigger another instance (unless that's checked/prevented) but basically when I use a computer I modify files all the time and I worry "FreeFileSync.exe" would get triggered and compare all the time in the background.
By comparizon, I think Dropbox and others for example just deal with freshly modified files.
You don't need to tell me that Dropbox does something else; it's similar and I don't care it may not be same thing completely.
Point is; I can't use the RealTimeSync if it will trigger the whole big comparison/sync every time a file is modified.
I hope I'm wrong.
Thanks,
Cat

[Cat]

Why no answer, please? Nobody knows? Is it a stupid question?

[Radish]

It's not a stupid question and I'm waiting in hope that it gets an answer too.

I did read the manual entry on RealTimeSync but I don't think it really answers your question: https://freefilesync.org/manual.php?topic=realtimesync

[Plerry]

Any change in the RTS monitored folder(s) will launch the specified application, normally FFS.
As long as an FFS instance launched by a given RTS instance is running, further monitoring for changes by the given RTS instance is suspended as long as said FFS instance is running.
FFS always compares all folders/files included in its sync definition.

If you are afraid running these FFS compares is too time consuming, you may consider to split your RTS monitoring and FFS syncing into multiple, non-overlapping, corresponding parts.
A change in one such part detected by RTS will then trigger an FFS compare and sync on that part only, limiting the amount of folders/files to be compared.

[Cat]

Thank you Plerry.
That's a workaround that might work in some situations but it's not ideal.
I don't develop this kind of things so I may be wrong, but if the program gets notified by the OS of a change, doesn't that include the name of the change file? Couldn't it just sync that file?
Thanks,
Cat

[Plerry]

I don't know what info the OS makes available to RTS upon detecting a change.
But, as explained in the bottom paragraph of the RTS Manual page, RTS only launches its specified application (here FFS), once no new changes occur within the specified idle time after the last change. Consequently, multiple changes may have occurred before FFS is launched, not just a single one.
Likewise, monitoring by RTS is suspended while the FFS job launched by RTS is running.
Any files that changed while FFS is running are therefore not noticed by RTS, will not trigger a sync and will only be synced when FFS is run the next time.

Note that RTS and FFS are essentially separate applications.
RTS monitors changes and upon detecting such launches the specified application. This application commonly is FFS, but it may just as well be another application.
The comparison and syncing is done by FFS. The only link between RTS and FFS is that FFS is launched by RTS.

[Cat]

I had forgotten about that. I suppose if some optional parameters could be passed between RTS and FFS things could get better but I don't see it happening.
Maybe if I look at/change the RTS code I could just call some kind of COPY for just that file.
Thanks,
Cat