Basic concepts and definitions

As stated in the previous chapter, mapping is the process of defining how a document should be mapped to Elasticsearch (if you don't recall, please refer to the Mapping section in the previous chapter). How a field is tokenized, analyzed, and searchable can be found using the mapping mechanism. Keep in mind that mapping is actually a schema definition (we will examine it in detail at the end of this chapter).

Now let's review the basic concepts and definitions.

Metadata fields

All the fields are not returned to us when a document is requested but each document has auto-generated metadata fields with each mapping which have information about the document that allows us to control how the metadata document is indexed. For example, which fields will return with the query results, how long the document will live, and so on.

We will now examine some of those fields.

_source

We have already talked at length about the _source field in Chapter 1, Introduction...