[[nested-query]] === Querying a Nested Object
Because nested objects ((("nested objects", "querying")))are indexed as separate hidden documents, we can't query them directly. ((("queries", "nested"))) Instead, we have to use the http://bit.ly/1ziFQoR[`nested` query] or http://bit.ly/1IOp94r[`nested` filter] to access them:
GET /my_index/blogpost/_search { "query": { "bool": { "must": [ { "match": { "title": "eggs" }}, <1> { "nested": { "path": "comments", <2> "query": { "bool": { "must": [ <3> { "match": { "comments.name": "john" }}, { "match": { "comments.age": 28 }} ] }}}} ] }}}
<1> The title clause operates on the root document.
<2> The nested clause ``steps down'' into the nested comments field.
It no longer has access to fields in the root document, nor fields in
any other nested document.
<3> The `comments.name` and `comments.age` clauses operate on the same nested
document.
A nested field can contain other nested fields. Similarly, a nested
query can contain other nested queries. The nesting hierarchy is applied
as you would expect.
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Of course, a nested query could match several nested documents.
Each matching nested document would have its own relevance score, but these
multiple scores need to be reduced to a single score that can be applied to
the root document.
By default, it averages the scores of the matching nested documents. This can
be controlled by setting the score_mode parameter to avg, max, sum, or
even none (in which case the root document gets a constant score of 1.0).
GET /my_index/blogpost/_search { "query": { "bool": { "must": [ { "match": { "title": "eggs" }}, { "nested": { "path": "comments", "score_mode": "max", <1> "query": { "bool": { "must": [ { "match": { "comments.name": "john" }}, { "match": { "comments.age": 28 }} ] }}}} ] }}}
<1> Give the root document the _score from the best-matching
nested document.
A nested filter behaves much like a nested query, except that it doesn't
accept the score_mode parameter. It can be used only in filter context—such as inside a filtered query--and it behaves like any other filter:
it includes or excludes, but it doesn't score.