Problem/Motivation
In node_search_execute() there is this:
<?php
$query = db_select('search_index', 'i', array('target'=> 'slave'))->extend('SearchQuery')->extend('PagerDefault');
?>So there are two query extenders, each decorating the last. Pager needs to be last for paging to work correctly.
However, when execute() is called from PagerDefault, preExecute() is then called before execute() is called on the decorated extender (SearchQuery in this case) object. SearchQuery relies on adding a search_* tag in its execute() method.
By this point preExecute() has already been called from PagerDefault - this then runs hook_query_alter() and any hook_query_TAG_alter()s based on the tags. At this point the search_* tag has not yet been added. So unfortunately, E.g. hook_query_search_node_alter() will never get invoked. Also, hook_query_alter() implementations will never see the search_* tag.
Proposed resolution
Move the adding of search_* tags to preExecute() instead.
