filter preprocessing for performance improvement

[Eric Irrgang <erici@motown.cc.utexas.edu>]

I wonder if it might be reasonable for the slapd frontend to do some 
preprocessing of search filters to recognize no-ops and such.  Most 
specifically, any search filter of the form (&(objectclass=*)(filter2)) 
can be reduced to (filter2), right?

I have a problem in that the first time someone performs a search for 
'objectclass=*' after slapd is restarted, the server is really bogged down 
for a while.  Once the search has completed once, this is not a problem. 
I assume that's due to the IDL cache.  However, I currently have to keep 
the server unavailable after restarting slapd for upwards of half an hour 
while I do an 'objectclass=*' search the first time.

I suppose a followup might be some preevaluation of ACLs before performing 
easily-recognized searches.  For instance, the backend should not have to 
cope with a search for objectclass=* if the user doesn't have read access 
to anything as is often the case with an anonymous bind.

--
Eric Irrgang - UT Austin ITS Unix Systems - (512)475-9342