OpenSearch/docs/reference/search/request/fields.asciidoc

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[[search-request-fields]]
=== Fields
Allows to selectively load specific fields for each document represented
by a search hit. Defaults to load the internal `_source` field.
[source,js]
--------------------------------------------------
{
"fields" : ["user", "postDate"],
"query" : {
"term" : { "user" : "kimchy" }
}
}
--------------------------------------------------
The fields will automatically load stored fields (`store` mapping set to
`yes`), or, if not stored, will load the `_source` and extract it from
it (allowing to return nested document object).
`*` can be used to load all stored fields from the document.
An empty array will cause only the `_id` and `_type` for each hit to be
returned, for example:
[source,js]
--------------------------------------------------
{
"fields" : [],
"query" : {
"term" : { "user" : "kimchy" }
}
}
--------------------------------------------------
Script fields can also be automatically detected and used as fields, so
things like `_source.obj1.obj2` can be used, though not recommended, as
`obj1.obj2` will work as well.
[[partial]]
==== Partial
When loading data from `_source`, partial fields can be used to use
wildcards to control what part of the `_source` will be loaded based on
`include` and `exclude` patterns. For example:
[source,js]
--------------------------------------------------
{
"query" : {
"match_all" : {}
},
"partial_fields" : {
"partial1" : {
"include" : "obj1.obj2.*",
}
}
}
--------------------------------------------------
And one that will also exclude `obj1.obj3`:
[source,js]
--------------------------------------------------
{
"query" : {
"match_all" : {}
},
"partial_fields" : {
"partial1" : {
"include" : "obj1.obj2.*",
"exclude" : "obj1.obj3.*"
}
}
}
--------------------------------------------------
Both `include` and `exclude` support multiple patterns:
[source,js]
--------------------------------------------------
{
"query" : {
"match_all" : {}
},
"partial_fields" : {
"partial1" : {
"include" : ["obj1.obj2.*", "obj1.obj4.*"],
"exclude" : "obj1.obj3.*"
}
}
}
--------------------------------------------------