Hello all, the documentation of the random_page_cost configuration parameter says:
Although the system will let you set random_page_cost to less than seq_page_cost, it is not physically sensible to do so.
Source: https://www.postgresql.org/docs/current/runtime-config-query.html#RUNTIME-CONFIG-QUERY-CONSTANTS
However, I don't think this statement is true. Consider the situation where the randomly fetched pages are mostly (or even entirely) cached in RAM, but where the sequentially fetched pages must be mostly read from disk. An example for such a scenario is a database system which uses RAM-cached indices.
Such a database system would be best modeled with random_page_cost < seq_page_cost. Please correct me if I'm wrong.
Best regards Mathias Kunter
