bug#48950: 28.0.50; Gnus nnvirtual selection with positive prefix shows newest articles of component groups

[Alex Bochannek <alex@bochannek.com>]

Hello!

I am not sure if this behavior is intentional or not, but it surprised
me and I thought I'd ask before I invest time changing it.

When selecting an `nnvirtual' group with a numeric prefix, I see the
newest messages of each of its component groups and not the newest
messages of the combined group.

Example:

I have a group made up of four component groups. I do a 'C-u 2 0 <SPC>'
and I end up with the five most recent messages from each of the
groups. Below you see the dates of the 20 most recent messages when I
open the combined group on the left, compared to the 20 most recent
messages when I open it with prefix.

  Today, 06:06  Tuesday 20:55   
  Today, 06:19  Tuesday 20:59   
  Today, 06:44  Yesterday, 17:27
  Today, 06:45  Yesterday, 17:31
  Today, 07:27  Yesterday, 17:57
  Today, 07:31  Today, 01:15    
  Today, 08:13  Today, 02:34    
  Today, 08:30  Today, 02:41    
  Today, 09:02  Today, 02:44    
  Today, 09:18  Today, 04:57    
  Today, 10:00  Today, 09:02    
  Today, 10:01  Today, 10:00    
  Today, 10:45  Today, 10:45    
  Today, 10:51  Today, 10:51    
  Today, 11:15  Today, 11:15    
  Today, 11:32  Today, 11:32    
  Today, 12:05  Today, 12:05    
  Today, 12:13  Today, 12:13    
  Today, 12:27  Today, 12:27    
  Today, 12:56  Today, 12:56    

All messages on the left are from two high volume groups. The other two
groups don't show up on the left list at all and you can tell by the
time stamps that the first five messages on the right are from a low
volume group.

I can see some value to using the approach to show messages from all
groups, but that fails when I select fewer groups than there are
component groups. I may only see an older message from a low-volume
group instead of the one new message that was just posted to a
high-volume group.

Can you explain the expected behavior to me?

Thanks!

-- 
Alex.