What is the best schema design on one to many (1 to 10k) relationship mapping


I am facing problem and also I am new in ES. The problem is I have two entity, let's define X and Y.
X entity have 10 field (key) and Y have 15 field (key).

X and Y have one to many relationship. the problem is one document have around 100 to 10k of many relationship of Y document.

I want to search from Y based on X and also search X based on Y entity.

Let's say X.fname , X.lname , X.blogtitle, and Y.comment, Y.commentatorName. (this is just example , I have 10 field in X and Y have 15 filed) I want to search on every field.

Can any one suggest me or help me which is best schema design for this scenario.