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I am using the Tire gem for Rails and a couple of questions have been raised about model associations. How do you work with them? Let say you have a relation between a Person and a car. Each Person have many Cars. Now if you want to index the car objects too, how do you do that? How can you retrieve a person by searching for car.make for example?

In general, I can see that elasticsearch which is document centric doesn't have the same concepts that RDBMS have. One-to-one, one-to-many and many-to-many.

If you have a many-to-many relationship for instance and you want only objects with a property of the other end of the relationship that will be impossible? Is elastic search a better fit with a NoSQL database like MongoDB?

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There are many possible strategies how to model your data in Elasticsearch, including relationships. In Elasticsearch, there are at least three strategies for related data:

  1. Just use JSON and it's ability to fluently express hierarchies,
  2. for the situation where the Car is actually a list of cars, use the nested type,
  3. use parent/child support for situations where you need to index both entities individually.

With Tire, first check and try out in code this answer: Elasticsearch, Tire, and Nested queries / associations with ActiveRecord. It should contain all information needed for your scenario. The code is available also separately.

References:

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So it is actually possible to indes a models associations. Am I correct that the child objects are stored in the same type as their parents? Does Tire/elasticsearch do something magic to associate it with its parent so you don't have duplicated parent documenta? And also, is it possible to index a many to many relationship too? Do you query your object before you serialize it or something?
And I read the article on managing relations in elasticsearch. Does he mean to inline all relations in the same document? Is that the best and how do you do that with Tire?
My suggestion would be to "just inline" as much as you can. Tire does not (yet) provide any special support for modeling relationships with parent/child.

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