Nested Inner Hits

More info about inner hits is in the official elasticsearch docs

The nested inner_hits can be used to include nested inner objects as inner hits to a search hit. The actual matches in the different scopes that caused a document to be returned is hidden. In many cases, it’s very useful to know which inner nested objects caused certain information to be returned.

Simple example

{
    "query" : {
        "nested" : {
            "path" : "comments",
            "query" : {
                "match" : {"comments.message" : "[actual query]"}
            }
        }
    },
    "inner_hits" : {
        "comment" : {
            "path" : {
                "comments" : {
                    "query" : {
                        "match" : {"comments.message" : "[different query]"}
                    }
                }
            }
        }
    }
}

And now the query via DSL:

$matchQuery = new MatchQuery('comments.message', '[different query]');
$nestedQuery = new NestedQuery('comments', $matchQuery);
$searchQuery = new Search();
$searchQuery->add($matchQuery);
$innerHit = new NestedInnerHit('comment', 'comments', $searchQuery);

$search = new Search();
$search->addQuery(new MatchQuery('comments.message', '[actual query]'));
$search->addInnerHit($innerHit);
$search->toArray();

In the example above comment is the name of the inner hit, comments is the path to the nested field and $matchQuery is the actual query that will be executed.

Nesting inner hits

It is possible to nest inner hits in order to reach deeper levels of nested objects. Here is an example of nesting inner hits:

{
  "inner_hits": {
    "cars": {
      "path": {
        "cars": {
          "query": {
            "nested": {
              "path": "cars.manufacturers",
              "query": {
                "match": {
                  "cars.manufacturers.country": {
                    "query": "Japan"
                  }
                }
              }
            }
          },
          "inner_hits": {
            "manufacturers": {
              "path": {
                "cars.manufacturers": {
                  "query": {
                    "match": {
                      "cars.manufacturers.country": {
                        "query": "Japan"
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

And now the query via DSL:

$matchQuery = new MatchQuery('cars.manufacturers.country', 'Japan');
$matchSearch = new Search();
$matchSearch->addQuery($matchQuery);

$nestedQuery = new NestedQuery('cars.manufacturers', $matchQuery);
$nestedSearch = new Search();
$nestedSearch->addQuery($nestedQuery);

$innerHitNested = new NestedInnerHit('manufacturers', 'cars.manufacturers', $matchSearch);

$innerHit = new NestedInnerHit('cars', 'cars', $nestedSearch);
$nestedSearch->addInnerHit($innerHitNested);

$search = new Search();
$search->addInnerHit($innerHit);
$search->toArray();