How to get array size for each document

Elastic Stack Elasticsearch
2

Hello @ntsh999,

The "easiest" solution is using scripted fields, but it is gonna to be slow and consume resources, as you're accessing to the _source:

GET your_index_name/_search
{
  "script_fields": {
    "number_of_breaches": {
      "script": {
        "source": "params['_source'].breaches.length"
      }
    }
  },
  "_source": {
    "excludes": [ "breaches" ]
  }
}
# Response
{
  "took" : 672,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "mytest",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "contact" : 9899999999,
          "name" : "xyx",
          "age" : 45,
          "email" : ""
        },
        "fields" : {
          "number_of_breaches" : [
            1
          ]
        }
      }
    ]
  }
}

The best solution is usually to compute such fields at indexing time, for example using the Ingest Pipelines (documentation):

PUT _ingest/pipeline/count_breaches
{
    "description": "Counts the breaches",
    "processors": [
      {
        "script": {
          "source": "ctx.number_of_breaches = ctx.containsKey('breaches') ? ctx.breaches.length : 0"
        }
      }
    ]
}

The pipeline can be used when indexing the document.

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