Robert Haas <robertmh...@gmail.com> writes: > Whose mental model? I guess the Tom Lane mind is the canonical one > for this project, but I'm not sure that it entirely agrees with mine.
Since the fact that we have a notion of startup cost at all is entirely my fault, I don't feel shy about claiming to have the authoritative view of what it means. (Whether that's adequately documented is another question :-() > IIRC, it was previously proposed that we ought to charge > random_page_cost for the first block of a sequential scan, because at > present the cost of fetching 1 block differs depending on whether we > are fetching it from a heap or an index, which seems unprincipled. That might well be a sane thing to do ... but it'd still be part of run cost not startup cost. regards, tom lane