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Children Aggregation
editChildren Aggregation
editA special single bucket aggregation that selects child documents that have the specified type, as defined in a join
field.
This aggregation has a single option:
-
type
- The child type that should be selected.
For example, let’s say we have an index of questions and answers. The answer type has the following join
field in the mapping:
PUT child_example { "mappings": { "doc": { "properties": { "join": { "type": "join", "relations": { "question": "answer" } } } } } }
The question
document contain a tag field and the answer
documents contain an owner field. With the children
aggregation the tag buckets can be mapped to the owner buckets in a single request even though the two fields exist in
two different kinds of documents.
An example of a question document:
PUT child_example/doc/1 { "join": { "name": "question" }, "body": "<p>I have Windows 2003 server and i bought a new Windows 2008 server...", "title": "Whats the best way to file transfer my site from server to a newer one?", "tags": [ "windows-server-2003", "windows-server-2008", "file-transfer" ] }
Examples of answer
documents:
PUT child_example/doc/2?routing=1 { "join": { "name": "answer", "parent": "1" }, "owner": { "location": "Norfolk, United Kingdom", "display_name": "Sam", "id": 48 }, "body": "<p>Unfortunately you're pretty much limited to FTP...", "creation_date": "2009-05-04T13:45:37.030" } PUT child_example/doc/3?routing=1&refresh { "join": { "name": "answer", "parent": "1" }, "owner": { "location": "Norfolk, United Kingdom", "display_name": "Troll", "id": 49 }, "body": "<p>Use Linux...", "creation_date": "2009-05-05T13:45:37.030" }
The following request can be built that connects the two together:
POST child_example/_search?size=0 { "aggs": { "top-tags": { "terms": { "field": "tags.keyword", "size": 10 }, "aggs": { "to-answers": { "children": { "type" : "answer" }, "aggs": { "top-names": { "terms": { "field": "owner.display_name.keyword", "size": 10 } } } } } } } }
The above example returns the top question tags and per tag the top answer owners.
Possible response:
{ "took": 25, "timed_out": false, "_shards": { "total": 5, "successful": 5, "skipped" : 0, "failed": 0 }, "hits": { "total": 3, "max_score": 0.0, "hits": [] }, "aggregations": { "top-tags": { "doc_count_error_upper_bound": 0, "sum_other_doc_count": 0, "buckets": [ { "key": "file-transfer", "doc_count": 1, "to-answers": { "doc_count": 2, "top-names": { "doc_count_error_upper_bound": 0, "sum_other_doc_count": 0, "buckets": [ { "key": "Sam", "doc_count": 1 }, { "key": "Troll", "doc_count": 1 } ] } } }, { "key": "windows-server-2003", "doc_count": 1, "to-answers": { "doc_count": 2, "top-names": { "doc_count_error_upper_bound": 0, "sum_other_doc_count": 0, "buckets": [ { "key": "Sam", "doc_count": 1 }, { "key": "Troll", "doc_count": 1 } ] } } }, { "key": "windows-server-2008", "doc_count": 1, "to-answers": { "doc_count": 2, "top-names": { "doc_count_error_upper_bound": 0, "sum_other_doc_count": 0, "buckets": [ { "key": "Sam", "doc_count": 1 }, { "key": "Troll", "doc_count": 1 } ] } } } ] } } }