Mapping is a very important concept in Elasticsearch, as it defines how the search engine should process a document.
Search engines perform two main operations:
Indexing: This is the action to receive a document and store/index/process in an index
Searching: This is the action to retrieve the data from the index
These two parts are strictly connected. An error in the indexing step leads to unwanted or missing search results.
Elasticsearch has explicit mapping on an index/type level. When indexing, if a mapping is not provided, a default one is created, guessing the structure from the data fields that compose the document; then, this new mapping is automatically propagated to all cluster nodes.
The default type mapping has sensible default values, but when you want to change their behavior or you want to customize several other aspects of indexing (storing, ignoring, completion, and so on), you need to provide a new mapping definition.
In this chapter, we'll see all the possible types...