How to use set_items_per_page?
I have successfully used $view-&gt;set_items_per_page() in hook_views_pre_build(). The problem might be that in hook_views_pre_execute() the pager settings have already been built, so you might have to update those as well, with something like $view-&gt;display_handler-&gt;get_plugin('pager')-&gt;get_items_per_page().