RE: ldap query performance issue

[Chris Card <ctcard@hotmail.com>]

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> Date: Fri, 24 May 2013 07:48:55 -0700
> From: hyc@symas.com
> To: ctcard@hotmail.com; openldap-technical@openldap.org
> Subject: Re: ldap query performance issue
>
> Chris Card wrote:
>>>>> 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.
>
> You have to re-create all of the relevant indices as well. Also, it's always
> possible that some slots in your index are still too big, even for this
> increased size.
>
Thanks Howard.
I had to increase BDB_IDL_LOGN to 18 (also increasing the stack size) and rebuild the objectclass index, but the query is now sub-second.

> You should also test this query with your data loaded into back-mdb.
I intend to look at using back-mdb instead of back-bdb soon, as well as upgrading to the latest openldap release. When do you expect 2.4.36 to be available?

Chris