I'm facing a severe performance degradation of performance in 9.0.5

[cperezabo]

The same code (a simple loop that executes a few hundred save!) that runs in 2s with 9.0.4 takes more than 30s with 9.0.5.
I just switch versions in bundle, re run and performance goes to hell!
I had also updated Ruby to 3.4.1 and thought that could have been that but, after downgrading Ruby to the previous version, the issue was still there.

Update 1:
Ok, I started testing my code with every mongoid commit after the v9.0.4 tag and the issue was introduced in 86f49a5

Update 2:
I've installed 9.0.5 again, edited the gem by reverting just the change introduced in 86f49a5 and everything performs fine as always. So there it is the problem!

[comandeo-mongo]

Hi @cperezabo , thank you for raising the issue! We are sorry that you are experiencing problems with Mongoid, we'll take a look into it. I created JIRA ticket to track the work - https://jira.mongodb.org/browse/MONGOID-5848

[lucasDechenier]

@alcaeus @cperezabo @johnnyshields @comandeo-mongo

Hi everyone, I have an honest question:
Is there any major bug or known issue in Mongoid 9.0.4 that would make it a bad idea to lock the version there for the time being? Or does the performance regression still exist in that version as well?

[jamis]

@lucasDechenier The bugs fixed in 9.0.5 are listed in the release notes for that version, here: https://github.com/mongodb/mongoid/releases/tag/v9.0.5

If none of those affect you, you should be safe to lock to 9.0.4, since the change that @cperezabo noted was introduced in 9.0.5.

[johnnyshields]

@jamis Just to be doubly-clear about this, forcing users to lock to 9.0.4 is not an acceptable "SemVer" compliant solution here--we need a 9.0.6 which rolls back the performance regressions, even if it means rolling back the "fixes" that caused them.

[lucasDechenier]

@johnnyshields Completely agree — this kind of change should never have been included in a tiny release like 9.0.5.

Many projects (including ours) rely on automatic updates for patch versions, trusting that they won’t introduce breaking changes or major performance regressions. Releasing a fix like this in a patch version can silently harm production environments without warning — which is very dangerous.

@jamis @comandeo-mongo I strongly believe this issue should be addressed as soon as possible with a rollback release, so affected users can safely upgrade again without freezing to an older version.

[jamis]

@lucasDechenier thank you. We completely agree that this is an ugly regression, and it is high on our priority list. Freezing to an older version is a band-aid, and not a great one at that. Stay tuned.

[lucasDechenier]

I have the same problem, any solution?

[johnnyshields]

Looks like the rollback has been released, and this thread can be closed. Thanks Mongoid team 🙇‍♂️