1.Elasticsearch concepts

wikipedia talks about elasticsearch:
Elasticsearch is a search engine based on Lucene. It provides a distributed, multitenant-capable full-text searchengine with an HTTP web interface and schema-free JSON documents. Elasticsearch is developed in Java and is released as open source under the terms of the Apache License. Official clients are available in Java, .NET(C#), PHP, Python, Apache Groovy, Ruby and many other languages.[1] According to the DB-Engines ranking, Elasticsearch is the most popular enterprise search engine followed by Apache Solr, also based on Lucene.[2]

elasticsearch definition from elastic site:
Elasticsearch is a real-time distributed search and analytics engine. It allows you to explore your data at a speed and at a scale never before possible. It is used for full-text search, structured search, analytics, and all three in combination:
  • Wikipedia uses Elasticsearch to provide full-text search with highlighted search snippets, and search-as-you-type and did-you-mean suggestions.
  • The Guardian uses Elasticsearch to combine visitor logs with social -network data to provide real-time feedback to its editors about the public’s response to new articles.
  • Stack Overflow combines full-text search with geolocation queries and uses more-like-this to find related questions and answers.
  • GitHub uses Elasticsearch to query 130 billion lines of code.
reference documents:
http://solr-vs-elasticsearch.com/
https://www.elastic.co/guide/index.html
https://www.elastic.co/guide/en/elasticsearch/hadoop/6.4/install.html
https://www.elastic.co/guide/en/elasticsearch/guide/current/inverted-index.html

Elasticsearch glossary
https://www.elastic.co/guide/en/elasticsearch/reference/current/glossary.html
What is an Elasticsearch Index
    think of an index like a database.
  • MySQL => Databases => Tables => Columns/Rows
  • Elasticsearch => Indices => Types => Documents with Properties
  • MySQL ⇔ elasticsearch
  • Column ⇔  field
  • Row ⇔  document
  • Table ⇔  index
  • Schema ⇔  implicit
  • Catalog or database ⇔  cluster instance
  • Cluster ⇔  cluster
  • SQL query ⇔ query DSL
    cluster contains nodes which share the same cluster name.
    node: corresponding to one server that does hosting and implements indexing, querying.
    shard: stores document. A shard is a single Lucene instance. It is a low-level “worker” unit which is managed automatically by Elasticsearch.

    Elasticsearch installation

    2. Some practical on Elasticsearch

    https://www.elastic.co/blog/a-practical-introduction-to-elasticsearch

    3. Elasticsearch used in java application

    https://vitalflux.com/elasticsearch-create-query-delete-index-java-example/
    https://subhasishsahu.wordpress.com/2017/07/05/elastic-search-5-4-with-java-client/
    https://bytefish.de/blog/elasticsearch_java/
    https://www.pluralsight.com/blog/it-ops/elasticsearch-and-sql-server