Does the server have to scan the whole database on every query? If not, doesn't the disk access pattern tell you what the query was? I had thought you had to

Does the server have to scan the whole database on every query? If not, doesn't the disk access pattern tell you what the query was? I had thought you had to download the whole DB even for computational PIR, but hmm, maybe not in some cases where there is only 1 client with a secret.