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Cluster (cluster) and node (node)

A node is part of a cluster.

Index (Index), type (Type), document (Document) index: the collection type of a document with the same attribute: an index can define one or more types, and the document must belong to a type document: the document is the basic data unit Shard and Replica that can be indexed.

Fragmentation (shard)

Each index in ElasticSearch has multiple shards, and each shard is an Lucene index.

Function:

1. If the amount of data in an index is very large, it will cause great pressure on the hard disk and the bottleneck of search efficiency. Multiple fragments can be used to share the pressure.

two。 Fragmentation also allows users to scale horizontally and split and distribute operations, which can improve the efficiency of search and other operations.

Backup (replica): make a copy of a slice.

Function:

1. If the primary shard fails or has a problem, its backup shard can replace its work, thus improving the availability of ElasticSearch.

two。 You can also perform search operations through the backup fragments to share the search pressure.

Using RDMS thinking to understand ElasticSearch

Index: equivalent to database database

Type: equivalent to data table table

Document: equivalent to a record record in a table

RESTful API of ElasticSearch

ElasticSearch provides a simple and consistent set of RESTful API. The format is as follows

Http://:///

The commonly used HTTP verb GET/PUST/POST/DELETE

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