Index handling for oc_activity table

Following an article about PostgreSQL performance (Cache | Postgres Guide) I looked up the index hits for my nextcloud tables, and found an anomaly for the oc_activity table. Unlike all other “large” nextcloud tables (for my installation, there are about 10 tables with >20000 rows), the oc_activity table has an index hit ratio far below 99% (namely 45%!)

I suppose this can be a performance issue for nextcloud. And since the command add-missing-indices doesn’t output anything about the oc_activity table, I think it may be worthwhile to either review the index use for this table in the occ code (if existent) or add an index for this table by default (if non-existent).

Has anyone else come across this issue or do you have any idea how to fix this as a non-dev nextcloud admin?