When re-exporting chats with a large number of files or videos, users have to download a huge amount of data all over again. The same issue occurs during an unexpected interruption of the export process – all files have to be re-downloaded.
This impacts traffic consumption for both the client and the server. Additionally, it affects the export time – exporting data from several years can take several days or even longer. And with even the slightest failure, everything has to be downloaded again.
As is well known, Telegram stores a hash (checksum) for each file on its servers.
I suggest implementing a "resume export" feature. Specifically, when exporting to the same directory, if a file with the same name already exists on the disk, the application should check its hash against the one stored on Telegram's servers, and if they match, the file should not be downloaded again.
I believe this feature will improve both the user experience and the resource consumption of Telegram's servers.
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