Elasticsearch vs RDBMS concepts:
You can (roughly) think of an Elastic index like a RDBMS database.
- MySQL => Databases => Tables => Rows=>Columns
- Elasticsearch => Indices(database) => Types(tables) => Documents(rows) with Properties(columns)
An Elasticsearch cluster can contain multiple Indices (databases), which in turn contain multiple Types(tables). These types hold multiple Documents (rows), and each document has Properties(columns).
A ES mapping is like an RDBMS schema.
The three required Document metadata elements are as follows:
- Where the document lives is split into one or more Shards (partitions)
- The class of object that the document represents
- The unique identifier for the document
A Shard can have one or more replicas(copies).
Cluster is a collection of Shards and Replicas.