ElasticSearch–Searching through arrays of objects

To better understand how to search through array data in your ElasticSearch JSON document, it is important to know how ElasticSearch stores arrays behind the scenes.

Given a document which contains a ‘names’ array with a list of different name properties(e.g. firstname, lastname,…) using the following mapping:

	"names": {
	"properties": {
	"active": {
	"type": "boolean"
	},
	"companyname": {
	"type": "text",
	"fields": {
	"keyword": {
	"type": "keyword",
	"ignore_above": 256
	}
	}
	},
	"lastname": {
	"type": "text",
	"fields": {
	"keyword": {
	"type": "keyword",
	"ignore_above": 256
	}
	}
	},
	"firstname": {
	"type": "text",
	"fields": {
	"keyword": {
	"type": "keyword",
	"ignore_above": 256
	}
	}
	},
	"initials": {
	"type": "text",
	"fields": {
	"keyword": {
	"type": "keyword",
	"ignore_above": 256
	}
	}
	}
	}
	}

view raw mapping.json hosted with ❤ by GitHub

With the following sample data:

	{
	"names": [
	{
	"firstname": "James",
	"lastname": "Bond"
	},
	{
	"firstname": "Ethan",
	"lastname": "Hunt"
	}
	]
	}

view raw names.json hosted with ❤ by GitHub

When ElasticSearch indexes this document, it is stored like this:

	{
	"names.firstname": ["James","Ethan"],
	"names.lastname": ["Bond","Hunt"]
	}

view raw storednames.json hosted with ❤ by GitHub

Lucene has no concept of inner objects, so Elasticsearch flattens object hierarchies into a simple list of field names and values.

If you don’t want this behavior, you have to map the array as a nested object. Internally ElasticSearch maps these array objects as separate documents and does a child query.