r&d elasticsearch

ElasticSearch

Source

ElasticSearch is a NoSQL database, built with special algorithms to optimize data indexation and searches.

It also exposes a REST API on port 9200, that is useful to interact with the database.

Adding data

Adding data like this creates an index by the same way.

You can only have one type per index.

With POST: Generated ID url: localhost:9200/logs/my_app

{
	"timestamp": "2018-01-24 12:34:56",
	"message": "User logged in",
	"user_id": 4,
	"admin": false
}

Response:

{
   "_index":"logs",
   "_type":"my_app",
   "_id":"ZsWdJ2EBir6MIbMWSMyF",
   "_version":1,
   "result":"created",
   "_shards":{
      "total":2,
      "successful":1,
      "failed":0
   },
   "_seq_no":0,
   "_primary_term":1
}

With PUT: Chosen ID url: localhost:9200/app/users/4

{
  "id": 4,
  "username": "john",
  "last_login": "2018-01-25 12:34:56"
}

Response:

{
   "_index":"app",
   "_type":"users",
   "_id":"4",
   "_version":1,
   "result":"created",
   "_shards":{
      "total":2,
      "successful":1,
      "failed":0
   },
   "_seq_no":0,
   "_primary_term":1
}

There is no need to define the structure of the data beforehand. To ensure optimal performance, though, you can define Elasticsearch mappings according to data types.

Querying

Simple query by id

Method	URL
GET	localhost:9200/app/users/4

Response:

{
  "_index" : "app",
  "_type" : "users",
  "_id" : "4",
  "_version" : 1,
  "found" : true,
  "_source" : {
    "id" : 4,
    "username" : "john",
    "last_login" : "2018-01-25 12:34:56"
  }
}

Search query

Method	URL
GET	localhost:9200/_search?q=logged

{"took":173,"timed_out":false,"_shards":{"total":16,"successful":16,"skipped":0,"failed":0},"hits":{"total":1,"max_score":0.2876821,"hits":[{"_index":"logs","_type":"my_app","_id":"ZsWdJ2EBir6MIbMWSMyF","_score":0.2876821,"_source":
{
    "timestamp": "2018-01-24 12:34:56",
    "message": "User logged in",
    "user_id": 4,
    "admin": false
}
}]}}

Alternative queries:

Query	Description
username:johnb	Looks for documents where the username field is equal to “johnb”.
john*	Looks for documents that contain terms that start with john and is followed by zero or more characters.
john?	ooks for documents that contain terms that start with john followed by only one character.

Just adding /_search to the URL will return everything

List indexes

http://localhost:9200/_cat/indices?v&pretty

How we could add data for messages in Owly

Method	URL
POST	localhost:9200/CHATROOM_ID/message

{
    "authorUUID":"4A",
    "chatroomID":"CHATROOM_ID",
    "authorNAME":"Kassandra",
    "content":"It's raining in L.A :(",
    "timestamp":126890,
    "hasFileAttached":true,
    "attach":[
        {
            "fileName":"rain.png",
            "bucket":"CHATROOM_ID"
        }
    ],
    "isAnswer": true,
    "answersTo":"MESSAGE_ID"
}