Re: indexing objectclass: why?

[Roel van Meer <rolek@linvision.com>]

Julio Sánchez Fernández wrote:
> 
> Roel van Meer <rolek@linvision.com> writes:
> 
> > This helped. search times went down from 47 seconds to about 0.02
> > seconds.
> > Can anyone explain to me _why_ this influences performance so much?
> 
> There are special entries in the directory that may match your filter
> and, even logically part of your search universe, might not be
> contained physically in the backend database or searched subtree.
> 
> These entries are referrals and aliases.
> 
> Unless specific circumstances arise, slapd needs to retrieve those
> entries from the database to dereference or chase them to see if they
> match your search criteria.
> 
> It does this by artificially enhancing your search filter with
> objectclass searches.  Look in servers/slapd/back-ldbm/search.c,
> function search_candidates.
> 
> Well, it might be overkill in some cases, but that's the way it is
> implemented now.

> So if you don't have an objectclass index, many of your searches will
> suffer.

Thanks a lot, it makes sense now. I had hoped getting rid of the
referral stuff by compiling with --disable-referrals, but apparently it
didn't.

Thanks again,

Regards,
rolek

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