196 lines
5.7 KiB
Plaintext
196 lines
5.7 KiB
Plaintext
[discrete]
|
|
[[search-fields]]
|
|
=== Retrieve selected fields
|
|
|
|
By default, each hit in the search response includes the document
|
|
<<mapping-source-field,`_source`>>, which is the entire JSON object that was
|
|
provided when indexing the document. If you only need certain source fields in
|
|
the search response, you can use the <<source-filtering,source filtering>> to
|
|
restrict what parts of the source are returned.
|
|
|
|
Returning fields using only the document source has some limitations:
|
|
|
|
* The `_source` field does not include <<multi-fields, multi-fields>> or
|
|
<<alias, field aliases>>. Likewise, a field in the source does not contain
|
|
values copied using the <<copy-to,`copy_to`>> mapping parameter.
|
|
* Since the `_source` is stored as a single field in Lucene, the whole source
|
|
object must be loaded and parsed, even if only a small number of fields are
|
|
needed.
|
|
|
|
To avoid these limitations, you can:
|
|
|
|
* Use the <<docvalue-fields, `docvalue_fields`>>
|
|
parameter to get values for selected fields. This can be a good
|
|
choice when returning a fairly small number of fields that support doc values,
|
|
such as keywords and dates.
|
|
* Use the <<request-body-search-stored-fields, `stored_fields`>> parameter to get the values for specific stored fields. (Fields that use the <<mapping-store,`store`>> mapping option.)
|
|
|
|
You can find more detailed information on each of these methods in the
|
|
following sections:
|
|
|
|
* <<source-filtering>>
|
|
* <<docvalue-fields>>
|
|
* <<stored-fields>>
|
|
|
|
[discrete]
|
|
[[source-filtering]]
|
|
=== Source filtering
|
|
|
|
You can use the `_source` parameter to select what fields of the source are
|
|
returned. This is called _source filtering_.
|
|
|
|
.*Example*
|
|
[%collapsible]
|
|
====
|
|
The following search API request sets the `_source` request body parameter to
|
|
`false`. The document source is not included in the response.
|
|
|
|
[source,console]
|
|
----
|
|
GET /_search
|
|
{
|
|
"_source": false,
|
|
"query": {
|
|
"term": {
|
|
"user.id": "8a4f500d"
|
|
}
|
|
}
|
|
}
|
|
----
|
|
|
|
To return only a subset of source fields, specify a wildcard (`*`) pattern in
|
|
the `_source` parameter. The following search API request returns the source for
|
|
only the `obj` field and its properties.
|
|
|
|
[source,console]
|
|
----
|
|
GET /_search
|
|
{
|
|
"_source": "obj.*",
|
|
"query": {
|
|
"term": {
|
|
"user.id": "8a4f500d"
|
|
}
|
|
}
|
|
}
|
|
----
|
|
|
|
You can also specify an array of wildcard patterns in the `_source` field. The
|
|
following search API request returns the source for only the `obj1` and
|
|
`obj2` fields and their properties.
|
|
|
|
[source,console]
|
|
----
|
|
GET /_search
|
|
{
|
|
"_source": [ "obj1.*", "obj2.*" ],
|
|
"query": {
|
|
"term": {
|
|
"user.id": "8a4f500d"
|
|
}
|
|
}
|
|
}
|
|
----
|
|
|
|
For finer control, you can specify an object containing arrays of `includes` and
|
|
`excludes` patterns in the `_source` parameter.
|
|
|
|
If the `includes` property is specified, only source fields that match one of
|
|
its patterns are returned. You can exclude fields from this subset using the
|
|
`excludes` property.
|
|
|
|
If the `includes` property is not specified, the entire document source is
|
|
returned, excluding any fields that match a pattern in the `excludes` property.
|
|
|
|
The following search API request returns the source for only the `obj1` and
|
|
`obj2` fields and their properties, excluding any child `description` fields.
|
|
|
|
[source,console]
|
|
----
|
|
GET /_search
|
|
{
|
|
"_source": {
|
|
"includes": [ "obj1.*", "obj2.*" ],
|
|
"excludes": [ "*.description" ]
|
|
},
|
|
"query": {
|
|
"term": {
|
|
"user.id": "8a4f500d"
|
|
}
|
|
}
|
|
}
|
|
----
|
|
====
|
|
|
|
|
|
[discrete]
|
|
[[docvalue-fields]]
|
|
=== Doc value fields
|
|
|
|
You can use the <<docvalue-fields,`docvalue_fields`>> parameter to return
|
|
<<doc-values,doc values>> for one or more fields in the search response.
|
|
|
|
Doc values store the same values as the `_source` but in an on-disk,
|
|
column-based structure that's optimized for sorting and aggregations. Since each
|
|
field is stored separately, {es} only reads the field values that were requested
|
|
and can avoid loading the whole document `_source`.
|
|
|
|
Doc values are stored for supported fields by default. However, doc values are
|
|
not supported for <<text,`text`>> or
|
|
{plugins}/mapper-annotated-text-usage.html[`text_annotated`] fields.
|
|
|
|
.*Example*
|
|
[%collapsible]
|
|
====
|
|
The following search request uses the `docvalue_fields` parameter to
|
|
retrieve doc values for the following fields:
|
|
|
|
* Fields with names starting with `my_ip`
|
|
* `my_keyword_field`
|
|
* Fields with names ending with `_date_field`
|
|
|
|
[source,console]
|
|
----
|
|
GET /_search
|
|
{
|
|
"query": {
|
|
"match_all": {}
|
|
},
|
|
"docvalue_fields": [
|
|
"my_ip*", <1>
|
|
{
|
|
"field": "my_keyword_field" <2>
|
|
},
|
|
{
|
|
"field": "*_date_field",
|
|
"format": "epoch_millis" <3>
|
|
}
|
|
]
|
|
}
|
|
----
|
|
|
|
<1> Wildcard patten used to match field names, specified as a string.
|
|
<2> Wildcard patten used to match field names, specified as an object.
|
|
<3> With the object notation, you can use the `format` parameter to specify a
|
|
format for the field's returned doc values. <<date,Date fields>> support a
|
|
<<mapping-date-format,date `format`>>. <<number,Numeric fields>> support a
|
|
https://docs.oracle.com/javase/8/docs/api/java/text/DecimalFormat.html[DecimalFormat
|
|
pattern]. Other field datatypes do not support the `format` parameter.
|
|
====
|
|
|
|
TIP: You cannot use the `docvalue_fields` parameter to retrieve doc values for
|
|
nested objects. If you specify a nested object, the search returns an empty
|
|
array (`[ ]`) for the field. To access nested fields, use the
|
|
<<request-body-search-inner-hits, `inner_hits`>> parameter's `docvalue_fields`
|
|
property.
|
|
|
|
|
|
[discrete]
|
|
[[stored-fields]]
|
|
=== Stored fields
|
|
|
|
It's also possible to store an individual field's values by using the
|
|
<<mapping-store,`store`>> mapping option. You can use the
|
|
<<request-body-search-stored-fields, `stored_fields`>> parameter to include
|
|
these stored values in the search response.
|