Description of problem:

Customers are storing more and more data in LDAP.
In a recent customer ticket there we 21 million of entries and the IDL scan limit was set at the default value of 4000.
About 4300 entries ( 0.02 % ) were matching a filter, so the related search was unindexed.
In this peculiar case this was an internal search to build the ACI cache, thus the unindexed search
was causing a delay of 20 to 30 minutes before the LDAP server could be started. 


Version-Release number of selected component (if applicable):
$ grep 389-ds-base-1 installed-rpms 
389-ds-base-1.4.3.13-1.module+el8dsrv+8334+69a46a2e.x86_64  Sun Feb 28 18:01:43 2021
$

How reproducible:
Always.

Steps to Reproduce:
1. In a large DB, make sure to have more entries with the ldapsubentry objectClass than the IDL scan limit

2. The startup should take minutes due to an internal unindexed search that is used to build the ACI cache

Actual results:
Long startup time.

Expected results:
Fast startup.

Additional info:
This RFE is to evaluate if the default value could be increased ( maybe to 10K )
and if a dynamic behavior could be implemented ( X % of the total number of entries in a suffix would be indexed
with a hard limit of 50K? )