Pagination: Always a "sort" (of) mistake [bugfix]

Pagination is a key component on web-applications that let users navigate through pages making easy to read/find records. Also, pagination is a great strategy to improve performance by avoiding to load entire dataset at once. However, while working with Kaminari, a popular pagination gem in Rails, I encountered an unexpected issue that revealed an interesting edge case. Identify the issue Basically, pagination in frontend was not working properly. Datatable should load 316 total rows, although when the user started to load 15 records per page, frontend is showing inaccurate total rows. Multiple of 15 should ends at 0 or 5. There were pages with 64 records, crazy world. Some pages were loading 12 or 11 rows. There is no issues or error messages in the frontend or backend. Lost in debugging-land After discarding Angular frontend errors, I started to dig into backend controller and Kaminari configuration. Nothing seems wrong. Everything looked good: test suite, smoke tests, desktop debugging. Despite of test results, I started to wonder: what if returned-data is wrong after all? and... Bingo! Finally, after checking every response I noticed that there were duped records in two different pages(pagination requests). Those duped records were skipped from Angular data-table and that's why loaded/total rows did not match. Bingo: a sort of mistake This tricky bug has a simple explanation: bad sorting. Kaminari uses a SQL query using LIMIT/OFFSET strategy: SELECT * FROM posts ORDER BY id LIMIT 25 OFFSET 0 ORDER BY : sort the collection. LIMIT : number of records per page. OFFSET : is used to skip a specified number of rows before starting to return rows from a query. This works perfectly using ORDER BY id because primary key is unique. Check table A. id title body created_at lock 101 Welcome to the Platform First post introducing the new platform features. 2026-06-16 08:15:22 false 102 Summer Update Announcing the latest improvements and updates. 2026-06-16 08:15:22 true 103