[BE] [Bug]: Pagination with "Show Read Posts" disabled leads to skipped pages of content #3659

Requirements

• [X] Is this a bug report? For questions or discussions use https://lemmy.ml/c/lemmy_support
• [X] Did you check to see if this issue already exists?
• [X] Is this only a single bug? Do not put multiple bugs in one issue.
• [X] Is this a backend issue? Use the lemmy-ui repo for UI / frontend issues.

Summary

If you browse with show read posts enabled, and read every post on page 1 of content, when you navigate to page 2, it will show you page 2 of "unread" content, and you need to go back to page one.

Steps to Reproduce

1. Disable "Show Read Posts"
2. Browse a community

• I suggest a community with consistent content but a relatively static sort - e.g. !spaceporn@lemmy.fmhy.ml w/TopMonth

3. "Read" each post on the 1st page (e.g. upvote all of them)
   • Pay attention to top couple of posts on page
   • Notice vote counts at bottom of page
4. Browse to Page 2
   • Notice large drop in post vote count between end of page 1 and page 2
   • Pay attention to top couple of posts on page
5. Browse back to page 1
   • Notice vote counts at top of page and bottom of page aligns between the end of the original page 1 and the viewed page "2"
   • Notice Page 1 content is different from original page 1 content

Technical Details

I believe this is a pagination issue when constructing the offsets used for pagination, there may need to be a mechanism to deduct or track the state of read posts.

Version

BE: 18.

Lemmy Instance URL

lemmy.fmhy.ml