每次在弹性搜索中插入文档时自动增加字段值

Question

I have a requirement to generate a unique number (ARN) in this format

DD/MM/YYYY/1, DD/MM/YYYY/2

and insert these in elastic search index.

The approach i am thinking of is to create an auto increment field in the doc and use it to generate a new entry and use the new auto generated number to create the ARN and update the doc.

doc structure that i am planning to use:

{ id: 1, arn: 17/03/2018/01 }

something like this.

How can i get auto increment field in elastic search?

Answer 1

It can't be done in a single step. First you have to insert the record into the database, and then update the ARN with it's id

Answer 2

There is no auto-increment equivalent, for example, to hibernate id generator. You could use the Bulk API (if you have to save multiple documents at a time) and increase the _id and the ending of your ARN value programmatically.

Note: if you want to treat your id as a number , you should implement it yourself (in this example, I added a new field "my_id", because the _id of the documents is treated as a string.

POST /bulk
{ "index" : { "_index" : "your_index", "_type" : "your_type", "_id" : "1" } }
{ "arn" : "2018/03/17/1", my_id: 1 }
{ "index" : { "_index" : "your_index", "_type" : "your_type", "_id" : "2" } }
{ "arn" : "2018/03/17/2", my_id: 2 }

Then, the next time that you want to save new documents, you query for the maximum id something like:

POST /my_index/my_type/_search?size=1
{
  "query": {
       "fields": ["my_id"],
        "sort": [{
           "my_id": { "order": "desc" } }
        ]
   }
}

If your only requirement is that this ARN should be unique, you could also let elasticsearch calculate your _id by simply not setting it. Then you could relay at some unique token generator ( UID.randomUUID().toString() if work with java). Pseudo code follows:

String uuid = generateUUID() // depends on the programming language 
String payload = "{ \"arn\" : + uuid + "}" // concatenate the payload
String url = "http://localhost:9200/my_index" // your target index

executePost(url, payload) // implement the call with some http client library