core_course_search_courses web service can consume all php memory

We have a site with 101,334 courses when doing the following actions in Moodle we get out of memory issues:

1. Navigate to the global search page
2. Expand the Filter section
3. Click to open the Courses select

Expected outcome: A list of courses is displayed

Actual outcome: Eventually there is a JavaScript error and the Moodle session is killed (at least on out servers where we are using memcache sessions).

I was able to do this on a user with a site level role that gave access to all courses.

On our site this will also happen with any sufficiently broad search term for example a single letter. The only work around seems to be to paste in a full search term straight away into the course box so the number of courses found is reasonably small.