On 9/21/07, Tom Lane <[EMAIL PROTECTED]> wrote:
> so this example is getting past the heuristic tests in
> heap_page_prune_opt almost every time. Why is that? Too tired to poke
> at it more tonight.
I guess you already know the answer now, but anyways: Since we are
updating a single tuple in a single transaction, each update is preceded
by a sequential scan. All but last pages are completely full and marked
prunable, so HOT would try to (unsuccessfully) prune every (except may
be last) page.