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.
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 ...