Rake posts:reorder_posts gives `UniqueViolation` error

Moin · December 10, 2024, 9:57am

In Unable to move posts between topics - #2 by nat a fix for this error was announced.

github.com/discourse/discourse

FIX: When moving posts between topics, ensure only relevant timings are moved

discourse:main ← discourse:pento/fix-moving-posts-to-topic-chronologically

opened 03:01AM - 09 Dec 24 UTC

pento

+45 -1

## ✨ What's This? When moving posts to an existing topic whilst preserving ch…ronological ordering, the second chunk of posts moved can trigger a PostgreSQL error: ``` PG::UniqueViolation (ERROR: duplicate key value violates unique constraint "post_timings_unique" DETAIL: Key (topic_id, post_number, user_id)=(36, 29, 1) already exists. ) lib/mini_sql_multisite_connection.rb:109:in `run' app/models/post_mover.rb:432:in `copy_shifted_post_timings_from_temp' app/models/post_mover.rb:118:in `handle_moved_references' app/models/post_mover.rb:94:in `move_posts_to' app/models/post_mover.rb:28:in `block in to_topic' app/models/post_mover.rb:28:in `to_topic' ``` The cause of this error is a little bit silly. After a post has been moved from a different topic, a moderator post is inserted into the old topic, pointing to where the post has been moved to. This moderator post is ultimately created using `PostCreator`, which by default, records a 5000ms Post Timing for that newly created post. Because of how Post Timings are tracked, this timing will be inserted into the `post_timings` table with the same `topic_id`, `post_number`, and `user_id` as the moved post used to have before it was moved. Now, when we proceed to moving the next post, `PostMover.move_post_timings` will look for post timings to move based on whether there's a corresponding entry in the `moved_posts` table. This is where our problem lays: the post that we previously moved has an entry in the `moved_posts` table, but now there's an unexpected entry in `post_timings` that we know doesn't belong to the previously moved post, but it has matching `topic_id`, `post_number`, and `user_id` of the what that moved post used to have, anyway. To fix this, we can enforce only matching post IDs that are being moved in this run of `PostMover`. Internal ref t/142010/5 ## 👑 Testing The simplest way to reproduce this error is: - Create a destination topic. - Create the first source topic, and add a reply to it. - Create a second source topic, and add a reply to it. - Move the reply in the second source topic to the destination topic, remembering to check the “preserve chronological order” option. - Move the reply in the first source topic to the destination, again checking the “preserve chronological order” option.

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Rake posts:reorder_posts gives `UniqueViolation` error

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