""So,

when you are alone on the db, the buffer cache will fill with the data from the table, but will be replaced by new blocks during the following reads. ""


ok, will the data that fills the buffer first send to user then those buffer are overwritten by more data and then send back again to user again then be overwritten again and so on until all data are sent to user? (10 million rows each go)

OR

All data will send in a go to user, i.e all 100 million rows