Re: kill_prior_tuple for bitmap scan

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote
>
> Really? An indexscan will release pin before returning no-more-tuples,
> and had better do so else we leak pins during queries involving many
> indexscans.
>

I guess I see your point. For the scan stages not returning no-more-tuples,
we can do kill, but the problem is that most bitmap index scan can finish in
just one round :-(.

>
> Not sure I believe that either. Even granting the assumption that the
> pages are still in cache, this implies a big increase in bufmgr traffic.
>

If you mean the bufmgr traffic is on the BufMappingLock, then I don't worry
too much. Notice that we can have a list of buffer_ids that we are
interested in, we can pin/recheck-buftag of these targets without asking
bufmgr where are they. If we missed, then unpin and forget them is ok.

Regards,
Qingqing