Description

When selecting any kind of sort for the /_synapse/admin/v1/rooms endpoint, the sorting is unstable.

Steps to reproduce

• Call /_synapse/admin/v1/rooms?order_by=creator (or any other field that has a lot of the same values)
• Note down the IDs, considering these are unique
• Call /_synapse/admin/v1/rooms?from=xxx&order_by=creator
• Carefully check the returned IDs. At some point, already seen IDs are returned again.

This happens, in my case, for creator, since I have about 1000 rooms created by an application service. These all carry the same creator and thus, at least for PostgreSQL, the sorting of rows from the same creator is arbitrary.

I expect that, when I sort on something, and select a new page, I get new results that haven't been seen before.

Version information

• Homeserver: matrix.sonck.nl

If not matrix.org:

• Version: 1.49.2

• Install method: Docker Image

• Platform: Kubernetes on Linux