Currently random_page_cost is a GUC. I propose that this could be set per-table.
I think this is a good idea for widely-wanted planner hints. This way You can say "I do NOT want this table to be index-scanned, because I know it is not cached" by setting it`s random_page_cost to a large value (an obviously You can do the other way around, when setting the random_page_cost to 1 You say "I don`t care how You fetch the pages, they are all in cache") The value for the per-table setting could be inferred from pg_stat(io)?.*tables . We could have a tool to suggest appropriate values. We could call it something like cached_percentage (and have the cost of a random tuple fetch be inferred from the global random_page_cost, seq_tuple_cost and the per-table cached_percentage). Then we could set the global random_page_cost to a sane value like 200. Now one can wonder why the planner works while having such blantantly unrealistic values for random_page_cost :) What do You think? Greetings Marcin Mank -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
