Some features of Postgres require filesystem access. For example, per the manual, custom full-text search configurations need to read synonym lists from
Is it possible to create such a file in Render’s Postgres services?
According to Databases | Render · Cloud Hosting for Developers one of the pre-installed extensions is
dict_xsyn, which I think really only makes sense if you can create these files.
I’m not getting my hopes up too high, though – both AWS RDS (hxxps://forums.aws.amazon.com/thread.jspa?threadID=143920) and GCP Cloud SQL (hxxps://issuetracker.google.com/65624669) also have this issue