Optimization for the expireover procedure.

[Kirill Berezin]

Hie workers.

As far as I can see the current expiration procedure is based on lookup 
of all articles of a group, that is we look through the list of groups 
and check all articles for a group starting from lowest number. It is a 
good approach, because we remove all ill articles, but it is extremely slow.

I think that it is possible to speedup an expiration of the overview by 
looking articles through the time of arrival rather look through the 
group. For example, we can keep  a list of  all incoming  articles, just 
like history: time of arrival, group id and article number, sorted  by 
the time of arrival,  look through this list starting from the oldest 
article to newest one and apply group-based expiry to each article. It 
seems this requires rather simple extension to current storage modules.

Any suggestions, complaints?

kirill