(Complex) Nested vs. (Simple) Separated Selectors

Consider the following selectors, with the result of the first two used as parameters in the third:

Facility[] fs1 = Facility:equals(active,”yes”);
Immrecord[] im2 = Immrecord:lessThan(lastvisitdate, Mez:today());
Children[] cs1 = and(
	relationshipIn(facility, fs1),
	relationshipIn(immrecord, im2)
);

We distinguish between complex and simple selectors as complex selectors consisting of multiple nested selectors. The following, therefor, is the complex selector version of the above snippet.

Children[] cs1 = and(
	relationshipIn(facility, Facility:equals(Active,”yes”)),
	relationshipIn(immrecord, Immrecord:lessThan(lastvisitdate, Mez:today()))
);

This complex selector is more performant, potentially far more so. The reason is given in Lesson 10 of the Beginner's Tutorial, section "A Note on Complex Selectors":

Another example can be seen at the above link.