Can't run REST core_course_get_courses due to memory

by Matthew Davidson.  

We have ~8000 mdl_course rows and when we attempt to run a REST API call for core-course_get_courses, it errors out with a 500 because it is exhausting our ram.  We have tested up to 16gb of ram allocated to PHP.  This seems like an insane amount of memory to deliver a table that is only 6MB on the disc.

Any idea what could be happening?