Except that in the specific example I have (this is my post), the results of the inner select (I would assume) should be cached because the condition in the inn

Except that in the specific example I have (this is my post), the results of the inner select (I would assume) should be cached because the condition in the inner select is a fixed set of criteria, not related at all to the outer records. Also of interest is that NOT IN(insert subselect here) doesn't raise the same issue. Additionally it prevents the entire query from using any indices... I have lots of interesting query planner results from this particular go around. Also it's been fixed in 6.0-alpha just not back-ported, so I'm not sure I agree here.