286 lines
10 KiB
Plaintext
286 lines
10 KiB
Plaintext
[[search-request-inner-hits]]
|
|
=== Inner hits
|
|
|
|
The <<mapping-parent-field, parent/child>> and <<mapping-nested-type, nested>> features allow the return of documents that
|
|
have matches in a different scope. In the parent/child case, parent document are returned based on matches in child
|
|
documents or child document are returned based on matches in parent documents. In the nested case, documents are returned
|
|
based on matches in nested inner objects.
|
|
|
|
In both cases, 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 (in the case of nested or children or parent documents), or (in the case
|
|
of parent/child) caused certain information to be returned. The inner hits feature can be used for this. This feature
|
|
returns per search hit in the search response additional nested hits that caused a search hit to match in a different scope.
|
|
|
|
Inner hits can be used by defining a `inner_hits` definition on a `nested`, `has_child` or `has_parent` query and filter.
|
|
The structure looks like this:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
"inner_hits" : {
|
|
"<query>" : {
|
|
"inner_hits" : {
|
|
<inner_hits_options>
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
|
|
If `_inner_hits` is defined on a query that supports it then each search hit will contain a `inner_hits` json object with the following structure:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
"hits": [
|
|
{
|
|
"_index": ...,
|
|
"_type": ...,
|
|
"_id": ...,
|
|
"inner_hits": {
|
|
"<inner_hits_name>": {
|
|
"hits": {
|
|
"total": ...,
|
|
"hits": [
|
|
{
|
|
"_type": ...,
|
|
"_id": ...,
|
|
...
|
|
},
|
|
...
|
|
]
|
|
}
|
|
}
|
|
},
|
|
...
|
|
},
|
|
...
|
|
]
|
|
--------------------------------------------------
|
|
|
|
==== Options
|
|
|
|
Inner hits support the following options:
|
|
|
|
[horizontal]
|
|
`from`:: The offset from where the first hit to fetch for each `inner_hits` in the returned regular search hits.
|
|
`size`:: The maximum number of hits to return per `inner_hits`. By default the top three matching hits are returned.
|
|
`sort`:: How the inner hits should be sorted per `inner_hits`. By default the hits are sorted by the score.
|
|
`name`:: The name to be used for the particular inner hit definition in the response. Useful when multiple inner hits
|
|
have been defined in a single search request. The default depends in which query the inner hit is defined.
|
|
For `has_child` query and filter this is the child type, `has_parent` query and filter this is the parent type
|
|
and the nested query and filter this is the nested path.
|
|
|
|
Inner hits also supports the following per document features:
|
|
|
|
* <<search-request-highlighting,Highlighting>>
|
|
* <<search-request-explain,Explain>>
|
|
* <<search-request-source-filtering,Source filtering>>
|
|
* <<search-request-script-fields,Script fields>>
|
|
* <<search-request-fielddata-fields,Fielddata fields>>
|
|
* <<search-request-version,Include versions>>
|
|
|
|
[[nested-inner-hits]]
|
|
==== Nested inner hits
|
|
|
|
The nested `inner_hits` can be used to include nested inner objects as inner hits to a search hit.
|
|
|
|
The example below assumes that there is a nested object field defined with the name `comments`:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"query" : {
|
|
"nested" : {
|
|
"path" : "comments",
|
|
"query" : {
|
|
"match" : {"comments.message" : "[actual query]"}
|
|
},
|
|
"inner_hits" : {} <1>
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
|
|
<1> The inner hit definition in the nested query. No other options need to be defined.
|
|
|
|
An example of a response snippet that could be generated from the above search request:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
...
|
|
"hits": {
|
|
...
|
|
"hits": [
|
|
{
|
|
"_index": "my-index",
|
|
"_type": "question",
|
|
"_id": "1",
|
|
"_source": ...,
|
|
"inner_hits": {
|
|
"comments": { <1>
|
|
"hits": {
|
|
"total": ...,
|
|
"hits": [
|
|
{
|
|
"_type": "question",
|
|
"_id": "1",
|
|
"_nested": {
|
|
"field": "comments",
|
|
"offset": 2
|
|
},
|
|
"_source": ...
|
|
},
|
|
...
|
|
]
|
|
}
|
|
}
|
|
}
|
|
},
|
|
...
|
|
--------------------------------------------------
|
|
|
|
<1> The name used in the inner hit definition in the search request. A custom key can be used via the `name` option.
|
|
|
|
The `_nested` metadata is crucial in the above example, because it defines from what inner nested object this inner hit
|
|
came from. The `field` defines the object array field the nested hit is from and the `offset` relative to its location
|
|
in the `_source`. Due to sorting and scoring the actual location of the hit objects in the `inner_hits` is usually
|
|
different than the location a nested inner object was defined.
|
|
|
|
By default the `_source` is returned also for the hit objects in `inner_hits`, but this can be changed. Either via
|
|
`_source` filtering feature part of the source can be returned or be disabled. If stored fields are defined on the
|
|
nested level these can also be returned via the `fields` feature.
|
|
|
|
An important default is that the `_source` returned in hits inside `inner_hits` is relative to the `_nested` metadata.
|
|
So in the above example only the comment part is returned per nested hit and not the entire source of the top level
|
|
document that contained the the comment.
|
|
|
|
[[parent-child-inner-hits]]
|
|
==== Parent/child inner hits
|
|
|
|
The parent/child `inner_hits` can be used to include parent or child
|
|
|
|
The examples below assumes that there is a `_parent` field mapping in the `comment` type:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"query" : {
|
|
"has_child" : {
|
|
"type" : "comment",
|
|
"query" : {
|
|
"match" : {"message" : "[actual query]"}
|
|
},
|
|
"inner_hits" : {} <1>
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
|
|
<1> The inner hit definition like in the nested example.
|
|
|
|
An example of a response snippet that could be generated from the above search request:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
...
|
|
"hits": {
|
|
...
|
|
"hits": [
|
|
{
|
|
"_index": "my-index",
|
|
"_type": "question",
|
|
"_id": "1",
|
|
"_source": ...,
|
|
"inner_hits": {
|
|
"comment": {
|
|
"hits": {
|
|
"total": ...,
|
|
"hits": [
|
|
{
|
|
"_type": "comment",
|
|
"_id": "5",
|
|
"_source": ...
|
|
},
|
|
...
|
|
]
|
|
}
|
|
}
|
|
}
|
|
},
|
|
...
|
|
--------------------------------------------------
|
|
|
|
[[top-level-inner-hits]]
|
|
==== top level inner hits
|
|
|
|
Besides defining inner hits on query and filters, inner hits can also be defined as a top level construct alongside the
|
|
`query` and `aggregations` definition. The main reason for using the top level inner hits definition is to let the
|
|
inner hits return documents that don't match with the main query. Also inner hits definitions can be nested via the
|
|
top level notation. Other then that the inner hit definition inside the query should be used, because that is the most
|
|
compact way for defining inner hits.
|
|
|
|
The following snippet explains the basic structure of inner hits defined at the top level of the search request body:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
"inner_hits" : {
|
|
"<inner_hits_name>" : {
|
|
"<path|type>" : {
|
|
"<path-to-nested-object-field|child-or-parent-type>" : {
|
|
<inner_hits_body>
|
|
[,"inner_hits" : { [<sub_inner_hits>]+ } ]?
|
|
}
|
|
}
|
|
}
|
|
[,"<inner_hits_name_2>" : { ... } ]*
|
|
}
|
|
--------------------------------------------------
|
|
|
|
Inside the `inner_hits` definition, first the name if the inner hit is defined then whether the inner_hit
|
|
is a nested by defining `path` or a parent/child based definition by defining `type`. The next object layer contains
|
|
the name of the nested object field if the inner_hits is nested or the parent or child type if the inner_hit definition
|
|
is parent/child based.
|
|
|
|
Multiple inner hit definitions can be defined in a single request. In the `<inner_hits_body>` any option for features
|
|
that `inner_hits` support can be defined. Optionally another `inner_hits` definition can be defined in the `<inner_hits_body>`.
|
|
|
|
An example that shows the use of nested inner hits via the top level notation:
|
|
|
|
[source,js]
|
|
--------------------------------------------------
|
|
{
|
|
"query" : {
|
|
"nested" : {
|
|
"path" : "comments",
|
|
"query" : {
|
|
"match" : {"comments.message" : "[actual query]"}
|
|
}
|
|
}
|
|
},
|
|
"inner_hits" : {
|
|
"comment" : {
|
|
"path" : { <1>
|
|
"comments" : { <2>
|
|
"query" : {
|
|
"match" : {"comments.message" : "[different query]"} <3>
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
|
|
<1> The inner hit definition is nested and requires the `path` option.
|
|
<2> The path option refers to the nested object field `comments`
|
|
<3> A query that runs to collect the nested inner documents for each search hit returned. If no query is defined all nested
|
|
inner documents will be included belonging to a search hit. This shows that it only make sense to the top level
|
|
inner hit definition if no query or a different query is specified.
|
|
|
|
Additional options that are only available when using the top level inner hits notation:
|
|
|
|
[horizontal]
|
|
`path`:: Defines the nested scope where hits will be collected from.
|
|
`type`:: Defines the parent or child type score where hits will be collected from.
|
|
`query`:: Defines the query that will run in the defined nested, parent or child scope to collect and score hits. By default all document in the scope will be matched.
|
|
|
|
Either `path` or `type` must be defined. The `path` or `type` defines the scope from where hits are fetched and
|
|
used as inner hits. |