RU consumption doesn't seem correct

Question

I have a simple core sql query that gets a count of rows. If i do the EXISTS and the IN separately, it's around 2/3RUs, but if i do a (EXISTS "OR" IN), then it jumps up to 45RU. It makes more since for me to do 2 different queries than 1. Why does the OR cause the RU consuption to go up?

Example.

SELECT VALUE COUNT(1) FROM ROOT r.  -- 850 rows, 2-3RUs

SELECT VALUE COUNT(1) FROM ROOT r WHERE IS_NULL(r.deletedAt) -- 830 rows, 2-3RUs

SELECT VALUE COUNT(1) FROM ROOT r WHERE IS_NULL(r.deletedAt) AND r.id IN (......). 830 rows, 2-3RUs

SELECT VALUE COUNT(1) FROM ROOT r WHERE IS_NULL(r.deletedAt) AND EXISTS(SELECT s FROM s IN r.shared WHERE s.id = ID) -- 840rows, 2-3RUs

SELECT VALUE COUNT(1) FROM ROOT r WHERE IS_NULL(r.deletedAt) AND (EXISTS(SELECT s FROM s IN r.shared WHERE s.id = ID) OR r.id IN (...)) -- 840rows,  45RUs

Answer 1

I think last r.id IN() causes a Full Table Scan.