Document and Type:-
One row of a RDBMS is equal to the Document of ElasticSearch. Let take an example for understanding:-
“ID” : 1, “Name” : “Shiv”, “Age” : 19, “Gender” : “Male”
Here in Table one row of ID equal to 1 is same for the JSON data as describe in JSON. This Json is know as Document.
In RDBMS, when we provide any name to the table than it is know as table name. Same for the Elasticsearch it is known as type.
Index in ElasticSearch:-
RDBMS : Database
ElasticSearch : Index
In RDBMS, we have a database and the database contains mutiple tables and inside the table we have mutiple Data. Same for the ElasticSearch, we have Index. In Index we have multiple TYPE and inside the TYPE we have JSON. We can also say, Index is the collection of Documents.
Cluster in ElasticSearch:-
A Cluster is the collection of single or the multiple nodes which are combine together to store the entire data.
Node in ElasticSearch:-
As we know, Cluster is the combination of Nodes. Each node is known as the server which store the data and participates in the Indexing and search capabilities.
Shards in ElasticSearch:-
When we create any index and store the data into it than it split the index into multiple bucket which is known as Shards. It is done because elasticsearch can store the data in different nodes.
Replicas in ElasticSearch:-
ElasticSearch allow us to make copy of any of the Shards known as Replicas. We can also provide the name to each of the Replicas.