[hans_castorp]

I did not explicitly evict the Postgres buffer cache, but using pg_buffercache to evict all buffers for the table, yields a runtime of 23ms for me (still going for the BitmapOr).

https://notebin.de/?ac3fcf55e6850f47#ERXndRrqp3X4zEWX5EC3dZU...

Which plan does Postgres choose in your case that results 100ms?

[ethanseal]

Exactly the same one from what I see: https://github.com/ethan-seal/ors_expensive/blob/main/explai...

Given the buffer reads seem close to yours, I believe it's page cache.