On Wed, Feb 12, 2014 at 08:59:31PM +0100, Corinna Vinschen wrote: >On Feb 12 11:16, Ken Brown wrote: >> On 2/12/2014 4:08 AM, Corinna Vinschen wrote: >> >On Feb 11 19:06, Eric Blake wrote: >> >>On 02/11/2014 05:06 PM, Warren Young wrote: >> >>>On 2/11/2014 16:25, David Stacey wrote: >> >>>>getpwent() is called in three different places. >> >>> >> >>>To those of you who have investigated these code paths: do any of them >> >>>look like they couldn't be replaced by getpwnam() or other calls that >> >>>would let cygwin1.dll do single-record AD/SAM lookups, rather than >> >>>whole-table/tree scans? >> >>> >> >>>That is, do any of these programs really need to visit every record in >> >>>/etc/passwd? >> >> >> >>libreadline wants to know how to tab-complete ~foo; to do that, it has >> >>to find all usernames beginning with foo. How would you do that without >> >>visiting every single record? >> > >> >This seems to be the major usage of getpwent these days. The question >> >is, how bad is it if only a handful entries, or even only a single one >> >(of oneself) show up? >> > >> >Either way, implementing a full getpwent requires to return the local >> >users, the users of the primary domain, and the users of all trusted >> >domains. I know of domains with 200K users and there are probably >> >bigger ones. How long should a search take when a user presses <TAB> >> >after the ~? And then, shall the process running the getpwent actually >> >cache all of them? This seems really excessive. >> >> What about the following compromise: If /etc/passwd exists, then >> getpwent behaves as it does currently. > >This part is relatively easy to implement. > >> Otherwise, it returns a >> handful of entries, or possibly just the current user. > >The handful entries would be the ones the process has cached at that >point in time. The tricky part is that getpwent would have to keep >track which entries from the file are in the cache so that those are not >accidentally enumerated twice. > >> This gives >> users a choice. If tab-completion in this situation is important to >> them, they can keep their /etc/passwd file. > >There's only one tiny problem. Whatever I think about the full >enumerate being right or wrong, I have this vague feeling that I'd like >to have this implemented fully at one point. My cat disapproves, but we >can't agree on everything, I guess. Another configuration option in >/etc/nsswitch.conf might comfort her.
I don't know if this has been mentioned but would a cache help here, i.e., nscd? I think that's how Linux deals with this type of situation. cgf -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
