Signal takes up 2x space after Android Transfer

[skickar]

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• I have read https://github.com/signalapp/Signal-Android/wiki/Submitting-useful-bug-reports
• This isn't a feature request or a discussion topic

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Bug description

When transferring an account via Android Account transfer from an old phone with a a 65gb signal database, the Signal install on new phone takes up double that space (130 gb). Signal also appears to only see 65 gb internally, while the new phone sees Signal taking up 130 gb.

Steps to reproduce

• Transfer large signal database via Android account transfer to new phone
• Make sure backups are disabled so it does not create a new backup
• Complete setup on new phone and observe storage used reported inside Signal app
• Observe storage taken up by the whole app and note it's twice what Signal reports internally

Actual result: When transferring an account to a new Android phone, the Signal installation on the new phone takes up twice as much space as on the old phone, even with no backups enabled.
Expected result: When transferring an account to a new Android phone, the Signal installation on the new phone should be roughly the same size.

Screenshots

Device info

Device: Google Pixel 6 pro
Android version: 12
Signal version: 5.31.5

Link to debug log

Wasn't able to grab one right after the install, didn't notice till later

[greyson-signal]

So I have a theory that I'm relatively sure is correct. When you forward messages to multiple chats or just send the same exact attachment to multiple people in general, we will de-duplicate those attachments on disk. Unfortunately, this de-duplication is lost during the backup process because our current backup format doesn't really support it.

So if you send the same media to multiple chats somewhat often (or with large items, like videos), then I could definitely see it happening where the backup is much larger than your normal signal install (and thus your restore will be larger too).

We have some ideas to help with this, but they're larger projects that will require some thought.

[greyson-signal]

Closing as a duplicate of #11509. We'll track it there.