Thank you for your quick response. If idlexp is the accepted solution then I'd like to understand how to choose correct value for idlexp?
I have quickly tested with most values. With my quick tests I could not find any significant impact on performance. Setting idlexp to maximum 31 did however cause slapd to crash with segmentation fault on my system. Thanks, Petteri ________________________________ From: Quanah Gibson-Mount <[email protected]> Sent: Monday, August 16, 2021 23:19 To: Petteri Stenius <[email protected]>; [email protected] <[email protected]> Subject: Re: Index seems to return wrong amount of candidate causing really poor search performance --On Monday, August 16, 2021 9:07 PM +0000 [email protected] wrote: > Hello, > > We have experienced a similar issue. Unfortunately we too have a > confidential dataset we cannot share. > > Our dataset started slowing down at about 1.7m entries. With > slapcat/slapadd tools I can reliably reproduce the issue: > > - first I add about 1.7m entries with slapadd to an empty mdb database > - I test with a search operation that returns a single entry and it > performs as expected, about 0.06s - next I add a single entry with slapadd > - after this the exactly same search operation that returns a single > entry slows down significantly, about 1.37s > > With the new idlexp parameter set to for example value 17 this slow down > issue no longer happens with our dataset. > > I don't understand idlexp parameter well enough. My fear is that idlexp > tuning is not actually fixing this issue, instead the issue is simply > postponed. If setting idlexp fixed it, then the issue was that one additional entry caused the index to collapse to a range with the default idlexp value, which is why changing the setting had an effect since it would stop it from being a range at the higher idlexp value. I added documentation as to what the idlexp command does to the admin guide for OpenLDAP 2.5.6. You may want to read it, it applies to OpenLDAP 2.4 as well. <https://www.openldap.org/doc/admin25/slapdconf2.html#MDB%20Database%20Directives> Section 5.2.6.1 --Quanah -- Quanah Gibson-Mount Product Architect Symas Corporation Packaged, certified, and supported LDAP solutions powered by OpenLDAP: <http://www.symas.com>
