Overview changes

Russ Allbery rra at stanford.edu
Thu Nov 7 05:06:15 UTC 2002

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.

> 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?

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.

> Completely separate requirement :)

> To get the NFS reader stuff working I don't allow articles to arrive (on
> the readers) until they've been in the overview database for some
> seconds (basically to allow all the various caches to age out). To
> report the correct high water mark from GROUP I want to walk backwards
> from the most recent article until I find one which is old enough that
> we should report it.

Ah... hm.  Okay.  That's a bit more specialized, but I don't have any
fundamental objections, and I can see where it might be useful for other

Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

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