Relations between documents

While Elasticsearch is gaining more and more attention, it is no longer used as a search engine only. It is seen as a data analysis solution and sometimes as a primary data store. Having a single data store that enables fast and efficient full text searching often seems like a good idea. We not only can store documents, but we can also search them and analyze their contents bringing meaning to the data. This is usually more than we could expect from traditional SQL databases. However, if you have any experience with SQL databases, when dealing with Elasticsearch, you soon realize the necessity of modeling relationships between documents. Unfortunately, it is not easy and many of the habits and good practices from relation databases won't work in the world of the inverted index that Elasticsearch uses. You should already be familiar with how Elasticsearch handles relationships because we already mentioned nested objects and parent–child functionality in our Elasticsearch...