Elasticsearch Getting Started: Index/Document CRUD & Sear...

TL;DR

Scenario: ES zero foundation getting started, quickly complete index creation, document CRUD, search query
Conclusion: ES getting started simple, minimum example can run through in 3-10 minutes
Output: Complete CRUD operation examples, architecture concepts, error quick reference

ES Simple Usage

Create Index

PUT http://h121.wzk.icu:9200/wzk_blog01/?pretty

Return result:

{
  "acknowledged": true,
  "shards_acknowledged": true,
  "index": "wzk_blog01"
}

Insert Document

POST http://h121.wzk.icu:9200/wzk_blog01/_doc/1?pretty
{"id": "1", "title": "What is lucene"}

Return result:

{
    "_index": "wzk_blog01",
    "_id": "1",
    "_version": 1,
    "result": "created",
    "_shards": {
      "total": 2,
      "successful": 1,
      "failed": 0
    },
    "_seq_no": 0,
    "_primary_term": 1
}

Query Document

GET http://h121.wzk.icu:9200/wzk_blog01/_doc/1?pretty

Return result:

{
  "_index": "wzk_blog01",
  "_id": "1",
  "_version": 3,
  "_seq_no": 2,
  "_primary_term": 1,
  "found": true,
  "_source": {
    "id": "1",
    "title": "Apache Spark is a unified analytics engine for large-scale data processing"
  }
}

Update Document

POST http://h121.wzk.icu:9200/wzk_blog01/_doc/1?pretty
{"id": "1", "title": " What is elasticsearch"}

Return result:

{
  "_index": "wzk_blog01",
  "_id": "1",
  "_version": 4,
  "result": "updated",
  "_shards": {
      "total": 2,
      "successful": 1,
      "failed": 0
  },
  "_seq_no": 3,
  "_primary_term": 1
}

Search Document

POST http://h121.wzk.icu:9200/wzk_blog01/_search?pretty
{"query": {"match": {"title": "What"}}}

Return result:

{
  "query": {
    "match": {
      "title": "What"
    }
  }
}

Architecture and Concepts

Basic Introduction

Elasticsearch is a document-oriented distributed search and analysis engine, it can store and manage data as documents.

Comparison with Relational Database

Elasticsearch	MySQL
Index	Database
Type (removed in 7.x)	Table
Document	Row record
Field	Column

Core Concepts

Concept	Description
Index	Collection of documents with similar characteristics
Type	Logical classification/partition of index (removed after 7.x)
Field	Table field
Mapping	Defines each field’s type (schema)
Document	Basic information unit that can be indexed (JSON)
Near Real-time NRT	Slight delay from indexing document to searchable (usually within 1 second)
Cluster	Multiple nodes compose, identified by cluster name
Node	One ES instance
Shard	Horizontal partitioning of index (primary shard + replica shard)
Replica	Copy of primary shard, improves recovery capability and performance

Error Quick Reference

Symptom	Root Cause	Fix
?pertty invalid/error	Parameter spelling error	Change to `?pretty`
Create index invalid	Used GET to access /index	Use PUT `/{index}?pretty`
Insert document 405/400	Used GET to send JSON	Use POST/PUT `/{index}/_doc/{id}` and put JSON in request body
/{index}/_doc/_search/1 returns error	Endpoint wrong	Query by ID: GET `/{index}/_doc/{id}`; search: POST `/{index}/_search`
Search no results	Put query DSL in “return result” instead of request body	Put DSL in request body, POST `/_search`
HTTP/HTTPS mixed or CORS	http/https mixed under same domain	Unify protocol; if browser, configure CORS/reverse proxy
401/403 Unauthorized	8.x enables security by default	Enable built-in user/API Key, or authenticate via intranet/reverse proxy
index_not_found_exception	Index not created/name wrong	First PUT `/{index}` then write; check lowercase naming
version_conflict_engine_exception	Concurrent update	Use `_update` or optimistic locking with `if_seq_no/if_primary_term`
Cluster Red/shard allocation failed	Shard/disk issue	Free up disk, fix shards, adjust replica count