[Bug]: Error "An index with name "unique_bucket_store" was already defined" while updateing from 32.0.2 to 33.0.0

[Volker-K]

⚠️ 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

On our stageing instance, I made a proof of concept with Nextcloud Office App (richdocuments). Later I disabled and deleted this app.
Updateing the instance from 32.0.2 to 33.0.0 threw the error

Exception: Database error when running migration 33000Date20251023120529 for app core
An index with name "unique_bucket_store" was already defined on table "oc_preview_locations".
Update failed

while updating the database schema. Table oc_preview_locations has been created from Nextcloud Office. The error occurs with nextcloud office enabled, disabled and even after it is deleted.

Steps to reproduce

1. Install nextcloud office on NC 32.0.2
2. disable and delete the app
3. migrate to NC 33.0.0

Expected behavior

Updateing the instance should just work. Either after deleting Nextclod Office App the app's tables should be deleted or the core should not try to update tables that belong to an app.

Nextcloud Server version

32

Operating system

Other

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

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

Upgraded to a MAJOR version (ex. 31 to 32)

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

[joshtrichards]

Table oc_preview_locations has been created from Nextcloud Office. The error occurs with nextcloud office enabled, disabled and even after it is deleted.

Where do you see this? I don't see any evidence of that. That's a table managed by core and not related to Nextcloud Office.

And unique_bucket_store didn't exist until v33. The entire preview mapper isn't even in pre-v33.

Any other possible explanation? Like testing against an inadvertently already updated/restored database or something?

[Volker-K]

Where do you see this? I don't see any evidence of that. That's a table managed by core and not related to Nextcloud Office.

Then I misinterpreted thos tables. I've compared the database of our live stage and the one of our staging system and found some Nextcloud Office tables only on stageing. Since there were some settings concerning previews when we were testing it with the collabora CODE-container, I suspected those tables to be part of Nextcloud Office.

In fact, we tried to automate the NC update and ran several attempts to migrate to NC 33 from Feb. 25 on, but the database dump is from Feb. 24, is a pure NC 32.0.2 system.

I've had a look at the oc_previews and some entries are from January:

MariaDB [itkcloud]> select FROM_UNIXTIME(mtime) from oc_previews;
+----------------------+
| FROM_UNIXTIME(mtime) |
+----------------------+
| 2026-01-16 08:50:07  |
| 2026-01-16 08:50:09  |
| 2026-01-16 08:50:09  |
| 2026-01-16 08:50:10  |
| 2026-01-16 08:50:11  |
| 2026-01-16 08:50:11  |
| 2026-02-24 13:44:38  |
| 2026-02-24 13:44:39  |
| 2026-02-24 13:44:39  |
| 2026-02-24 13:44:41  |
| 2026-01-20 13:07:42  |
| 2026-01-20 13:07:42  |
| 2026-01-20 13:07:42  |
+----------------------+
13 rows in set (0,001 sec)

Possibly I didn't drop the database before recovering after the first test migration and the oc_preview* tables weren't dropped when importing the od version, but why are there entries from January when they came with NC 33 that was released just last week?

Anyway, our live environment doesn't have them and I suspect it was just from restoring the NC 32 database and keeping new tables. If the entries with a date prior to the publication of NC 33 are not suspicious, we can close the issue.

[joshtrichards]

With the restructure of the preview handling in v33 (#54543), existing previews get migrated to the new structure so those dates are expected.