Extending your index structure with additional internal information

All the information provided in the previous chapters gave us a good look at what ElasticSearch is capable of, both in terms of indexing and querying. But their coverage was not nearly complete. One thing we would like to discuss in more detail is the functionalities of ElasticSearch that are not used every day, but can make our life easier when it comes to data handling.

Note

Each of the following field types should be defined on an appropriate type level. So if you recall our sample mappings for our small library from Chapter 2, Searching Your Data, we would add any of the following types under the book type mappings.

The identifier field

As you recall, each document indexed in ElasticSearch has its own identifier and type. In ElasticSearch there are two types of internal identifiers for the documents.

The first one is the _uid field, which is the unique identifier of the document in the index and is composed of the document...