Overview changes

Alex Kiernan alexk at demon.net
Wed Nov 20 12:00:36 UTC 2002

Russ Allbery <rra at stanford.edu> writes:

> Alex Kiernan <alexk at demon.net> writes:
> > Russ Allbery <rra at stanford.edu> writes:
> >> This by itself doesn't make a lot of sense to me in that I can't see
> >> how the overview interface could support it in a way that would be any
> >> faster than just calling OVopensearch for the full range and then
> >> discarding anything below the lower arrival time bound.  But maybe it's
> >> intended for use in combination with the second one?
> > For ov3 (which is all I've implemented it for) it relies on the fact
> > that articles get numbered in order of arrival (thinks... have I
> > introduced a dependency between innd and the overview manager?).
> Note that this doesn't necessary hold in the presence of Xref slaving,
> although it should be okay in other circumstances, and even mostly for
> Xref slaving.

OK, I'll work something in for that when I manage to get time to merge
the code.

> > So once the .IDX mapped you can do a binary search through it to locate
> > a starting point, before starting the linear search. Like I said I
> > hacked it in, so currently the code I'm running does:
> >   OVopensearch()
> >   ov3binsearch()
> >   OVsearch()
> > Where ov3binsearch then advances search->cur based on the binary
> > required arrival time.
> > For other overview methods based on databases clearly you could add
> > another index, for buffindexed, I don't know.
> Ah, okay.  Out of curiosity, do you have any benchmarking on how much time
> this saves for heavy NEWNEWS usage?

Nothing formal, but we brought down our load average at peak times
from ~200 to ~40 - though more than half of our users use NEWNEWS.

> The basic idea seems reasonable to me, although there is a possibility
> that it won't return the same results as the current method given that
> there isn't a strict correlation between arrival time and article numbers.

I actually cheat and always pick an arrival time which is slightly too
early then weed those out using the existing check during the scan.

Alex Kiernan, Principal Engineer, Development, THUS plc

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