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From: ctcard@hotmail.com To: quanah@zimbra.com Subject: RE: ldap query performance issue Date: Thu, 23 May 2013 17:37:18 +0000
Date: Thu, 23 May 2013 10:06:51 -0700 From: quanah@zimbra.com To: ctcard@hotmail.com; openldap-technical@openldap.org Subject: Re: ldap query performance issue
--On Thursday, May 23, 2013 4:40 PM +0000 Chris Card ctcard@hotmail.com wrote:
Hi all,
I have an openldap directory with about 7 million DNs, running openldap 2.4.31 with a BDB backend (4.6.21), running on CentOS 6.3.
The structure of the directory is like this, with suffix dc=x,dc=y
dc=x,dc=y account=a,dc=x,dc=y mail=m,account=a,dc=x,dc=y // Users .... licenceId=l,account=a,dc=x,dc=y // Licences, objectclass=licence .... group=g,account=a,dc=x,dc=y // Groups .... // etc.
account=b,dc=x,dc=y ....
Most of the DNs in the directory are users or groups, and the number of licences is small (<10) for each account.
If I do a query with basedn account=a,dc=x,dc=y and filter (objectclass=licence) I see wildly different performance, depending on how many users are under account a. For an account with ~30000 users the query takes 2 seconds at most, but for an account with ~60000 users the query takes 1 minute.
It only appears to be when I filter on objectclass=licence that I see that behaviour. If I filter on a different objectclass which matches a similar number of objects to the objectclass=licence filter, the performance doesn't seem to depend on the number of users.
There is an index on objectclass (of course), but the behaviour I'm seeing seems to indicate that for this query, at some point slapd stops using the index and just scans all the objects under the account.
Any ideas?
Increase the IDL range. This is how I do it:
--- openldap-2.4.35/servers/slapd/back-bdb/idl.h.orig 2011-02-17 16:32:02.598593211 -0800 +++ openldap-2.4.35/servers/slapd/back-bdb/idl.h 2011-02-17 16:32:08.937757993 -0800 @@ -20,7 +20,7 @@ /* IDL sizes - likely should be even bigger
- limiting factors: sizeof(ID), thread stack size
*/ -#define BDB_IDL_LOGN 16 /* DB_SIZE is 2^16, UM_SIZE is 2^17 */ +#define BDB_IDL_LOGN 17 /* DB_SIZE is 2^16, UM_SIZE is 2^17 */ #define BDB_IDL_DB_SIZE (1<<BDB_IDL_LOGN) #define BDB_IDL_UM_SIZE (1<<(BDB_IDL_LOGN+1)) #define BDB_IDL_UM_SIZEOF (BDB_IDL_UM_SIZE * sizeof(ID))
Thanks, that looks like it might be the issue. Unfortunately I only see the issue in production, so patching it might be a pain.
I've tried this change, but it made no difference to the performance of the query.
Chris