Scenario A (single user restriction, single page):

Create a page without any child pages, and monitor the index queue. Add a view restriction to a single user, and notice that the index queue now has 3 entries added

Scenario B (multiple user restriction, single page):

Create a page without any child pages, and monitor the index queue. Add 2 view restrictions to 2 separate users, and notice that the index queue now has 6 entries added

Scenario C (multiple user restriction, page with 1 child):

Create a page, and add a child page, and monitor the index queue. Add 2 view restrictions to 2 separate users (to the parent page), and notice that the index queue now has 12 entries added

Scenario D (single group restriction, page with 1 child):

Create a page, and add a child page, and monitor the index queue. Add 1 view restriction to 1 group (to the parent page), and notice that the index queue now has 6 entries added

Notice from the scenarios above that the index queue is doubled, if you add a similar restriction to another user, on the same page, and that this effect is compounded with every child page. This is compounded for every attachment as well.

This is a serious performance impact on many large instances, especially when they are affected by this: https://jira.atlassian.com/browse/CONF-16866 . Some instances' queue entries may grow to a really large number in a very short time, resulting in outages, as the index cannot be cleared with subsequent flushes.

Workaround

Utilize Scenario D. Add the individual users you wish to restrict individually into a group instead, and restrict the pages to a group.