search progress control

[Howard Chu <hyc@symas.com>]

Dunno if there's already anything like this, I haven't bothered to search yet.

I was considering adding the progress meter to ldapadd. Then it was suggested 
that it might be useful for slapcat/ldapsearch as well. For ldapsearch we 
would need a means to tell the client how large the result set is expected to 
be. Currently it's easy for back-bdb/hdb to provide this number, because they 
just walk through an IDL of candidates where the IDL size is already known. Of 
course the real result set size may be smaller due to actual filter evaluation.

This seems to call for a control that we could attach to a search request 
"give me an estimate of the result set size and update me every N entries". 
The response control would be attached to the first entry and every N entries 
after that, with an updated estimate of the total number of results. A control 
like this would be particularly useful for administrators using GUIs to browse 
a large directory, to give feedback about when they will receive the complete 
set of entries, and give an opportunity to decide to abandon the search or 
continue.

Comments?
--
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/