Re: heap_page_prune comments

On Nov 2, 2011, at 11:27 AM, Robert Haas wrote:
> The following comment - or at least the last sentence thereof -
> appears to be out of date.
>
>        /*
>         * XXX Should we update the FSM information of this page ?
>         *
>         * There are two schools of thought here. We may not want to update FSM
>         * information so that the page is not used for unrelated
> UPDATEs/INSERTs
>         * and any free space in this page will remain available for further
>         * UPDATEs in *this* page, thus improving chances for doing HOT updates.
>         *
>         * But for a large table and where a page does not receive
> further UPDATEs
>         * for a long time, we might waste this space by not updating the FSM
>         * information. The relation may get extended and fragmented further.
>         *
>         * One possibility is to leave "fillfactor" worth of space in this page
>         * and update FSM with the remaining space.
>         *
>         * In any case, the current FSM implementation doesn't accept
>         * one-page-at-a-time updates, so this is all academic for now.
>         */
>
> The simple fix here is just to delete that last sentence, but does
> anyone think we ought to do change the behavior, now that we have the
> option to do so?

The fillfactor route seems to make the most sense here... it certainly seems to be the least surprising behavior.
--
Jim C. Nasby, Database Architect                   jim@nasby.net
512.569.9461 (cell)                         http://jim.nasby.net