How it works...

When Elasticsearch processes a new mapping and finds a _meta field, it stores it in the global mapping status and propagates the information to all the cluster nodes.

_meta is only used for storing purposes; it's not indexed and searchable.

It can be used for the following reasons:

• Storing type metadata
• Storing object relational mapping (ORM) related information
• Storing type permission information
• Storing extra type information (that is, icon filename used to display the type)
• Storing template parts for rendering web interfaces