OpenSearch/docs/reference/docs/get.asciidoc

[[docs-get]]
== Get API

The get API allows to get a typed JSON document from the index based on
its id. The following example gets a JSON document from an index called
twitter, under a type called tweet, with id valued 1:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1'
--------------------------------------------------

The result of the above get operation is:

[source,js]
--------------------------------------------------
{
    "_index" : "twitter",
    "_type" : "tweet",
    "_id" : "1",
    "_version" : 1,
    "found": true,
    "_source" : {
        "user" : "kimchy",
        "postDate" : "2009-11-15T14:12:12",
        "message" : "trying out Elasticsearch"
    }
}
--------------------------------------------------

The above result includes the `_index`, `_type`, `_id` and `_version`
of the document we wish to retrieve, including the actual `_source`
of the document if it could be found (as indicated by the `found`
field in the response).

The API also allows to check for the existence of a document using
`HEAD`, for example:

[source,js]
--------------------------------------------------
curl -XHEAD -i 'http://localhost:9200/twitter/tweet/1'
--------------------------------------------------

[float]
[[realtime]]
=== Realtime

By default, the get API is realtime, and is not affected by the refresh
rate of the index (when data will become visible for search).

In order to disable realtime GET, one can either set `realtime`
parameter to `false`, or globally default it to by setting the
`action.get.realtime` to `false` in the node configuration.

When getting a document, one can specify `fields` to fetch from it. They
will, when possible, be fetched as stored fields (fields mapped as
stored in the mapping). When using realtime GET, there is no notion of
stored fields (at least for a period of time, basically, until the next
flush), so they will be extracted from the source itself (note, even if
source is not enabled). It is a good practice to assume that the fields
will be loaded from source when using realtime GET, even if the fields
are stored.

[float]
[[type]]
=== Optional Type

The get API allows for `_type` to be optional. Set it to `_all` in order
to fetch the first document matching the id across all types.


[float]
[[get-source-filtering]]
=== Source filtering

added[1.0.0.Beta1]

By default, the get operation returns the contents of the `_source` field unless
you have used the `fields` parameter or if the `_source` field is disabled. 
You can turn off `_source` retrieval by using the `_source` parameter:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1?_source=false'
--------------------------------------------------

If you only need one or two fields from the complete `_source`, you can use the `_source_include`
& `_source_exclude` parameters to include or filter out that parts you need. This can be especially helpful
with large documents where partial retrieval can save on network overhead. Both parameters take a comma separated list
of fields or wildcard expressions. Example:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1?_source_include=*.id&_source_exclude=entities'
--------------------------------------------------

If you only want to specify includes, you can use a shorter notation:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1?_source=*.id,retweeted'
--------------------------------------------------


[float]
[[get-fields]]
=== Fields

The get operation allows specifying a set of stored fields that will be
returned by passing the `fields` parameter. For example:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1?fields=title,content'
--------------------------------------------------

For backward compatibility, if the requested fields are not stored, they will be fetched
from the `_source` (parsed and extracted). This functionality has been replaced by the
<<get-source-filtering,source filtering>> parameter.

Field values fetched from the document it self are always returned as an array. Metadata fields like `_routing` and
`_parent` fields are never returned as an array.

Also only leaf fields can be returned via the `field` option. So object fields can't be returned and such requests
will fail.

[float]
[[_source]]
=== Getting the _source directly

Use the `/{index}/{type}/{id}/_source` endpoint to get
just the `_source` field of the document,
without any additional content around it. For example:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1/_source'
--------------------------------------------------

You can also use the same source filtering parameters to control which parts of the `_source` will be returned:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1/_source?_source_include=*.id&_source_exclude=entities'
--------------------------------------------------

Note, there is also a HEAD variant for the _source endpoint to efficiently test for document existence.
Curl example:

[source,js]
--------------------------------------------------
curl -XHEAD -i 'http://localhost:9200/twitter/tweet/1/_source'
--------------------------------------------------

[float]
[[get-routing]]
=== Routing

When indexing using the ability to control the routing, in order to get
a document, the routing value should also be provided. For example:

[source,js]
--------------------------------------------------
curl -XGET 'http://localhost:9200/twitter/tweet/1?routing=kimchy'
--------------------------------------------------

The above will get a tweet with id 1, but will be routed based on the
user. Note, issuing a get without the correct routing, will cause the
document not to be fetched.

[float]
[[preference]]
=== Preference

Controls a `preference` of which shard replicas to execute the get
request on. By default, the operation is randomized between the shard
replicas.

The `preference` can be set to:

`_primary`:: 
	The operation will go and be executed only on the primary
	shards.

`_local`:: 
	The operation will prefer to be executed on a local
	allocated shard if possible.

Custom (string) value:: 
	A custom value will be used to guarantee that
	the same shards will be used for the same custom value. This can help
	with "jumping values" when hitting different shards in different refresh
	states. A sample value can be something like the web session id, or the
	user name.

[float]
[[get-refresh]]
=== Refresh

The `refresh` parameter can be set to `true` in order to refresh the
relevant shard before the get operation and make it searchable. Setting
it to `true` should be done after careful thought and verification that
this does not cause a heavy load on the system (and slows down
indexing).

[float]
[[get-distributed]]
=== Distributed

The get operation gets hashed into a specific shard id. It then gets
redirected to one of the replicas within that shard id and returns the
result. The replicas are the primary shard and its replicas within that
shard id group. This means that the more replicas we will have, the
better GET scaling we will have.