[Bug]: files_reminders causing N+1 queries for folders with more than 512 elements

[salmart-dev]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Summary

OCA\FilesReminders\Dav\PropFindPlugin preloads reminders information for an entire collection during PROPFIND requests. ReminderService has a cacheFolder method which uses CappedMemoryCache as cache. The problem is that the default size for this cache is 512 meaning that if a directory has more than 512 files inside we start getting cache misses and start querying the DB.

What's worse is that once the condition hits, it always voids the pre-cached data and causes N+1 queries because:

• the preload mechanism starts caching reminders for all files in a directory
• once the limit of the CappedMemoryCache is reached, the information that was cached earlier is discarded
• when the PROPFIND is serialized into XML, the first file is no longer in the cache, causing a query for the single file
• the result is cached, pushing another older result out of the cache

Steps to reproduce

1. Create a folder
2. Upload more than 512 files
3. Do a PROPFIND request on the folder
4. See that the code runs >512 queries targeting the reminders table

Expected behavior

Queries are executed in N+1 way only if there are more than 512 reminders in files in a folder.

Nextcloud Server version

35 (master)

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response