Get API
editGet API
editThe 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 _doc
, with id valued 0:
GET twitter/_doc/0
The result of the above get operation is:
{ "_index" : "twitter", "_type" : "_doc", "_id" : "0", "_version" : 1, "found": true, "_source" : { "user" : "kimchy", "date" : "2009-11-15T14:12:12", "likes": 0, "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:
HEAD twitter/_doc/0
Realtime
editBy default, the get API is realtime, and is not affected by the refresh
rate of the index (when data will become visible for search). If a document
has been updated but is not yet refreshed, the get API will issue a refresh
call in-place to make the document visible. This will also make other documents
changed since the last refresh visible. In order to disable realtime GET,
one can set the realtime
parameter to false
.
Source filtering
editBy default, the get operation returns the contents of the _source
field unless
you have used the stored_fields
parameter or if the _source
field is disabled.
You can turn off _source
retrieval by using the _source
parameter:
GET twitter/_doc/0?_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:
GET twitter/_doc/0?_source_include=*.id&_source_exclude=entities
If you only want to specify includes, you can use a shorter notation:
GET twitter/_doc/0?_source=*.id,retweeted
Stored Fields
editThe get operation allows specifying a set of stored fields that will be
returned by passing the stored_fields
parameter.
If the requested fields are not stored, they will be ignored.
Consider for instance the following mapping:
PUT twitter { "mappings": { "_doc": { "properties": { "counter": { "type": "integer", "store": false }, "tags": { "type": "keyword", "store": true } } } } }
Now we can add a document:
PUT twitter/_doc/1 { "counter" : 1, "tags" : ["red"] }
- and try to retrieve it:
GET twitter/_doc/1?stored_fields=tags,counter
The result of the above get operation is:
{ "_index": "twitter", "_type": "_doc", "_id": "1", "_version": 1, "found": true, "fields": { "tags": [ "red" ] } }
Field values fetched from the document itself are always returned as an array.
Since the counter
field is not stored the get request simply ignores it when trying to get the stored_fields.
It is also possible to retrieve metadata fields like the _routing
field:
PUT twitter/_doc/2?routing=user1 { "counter" : 1, "tags" : ["white"] }
GET twitter/_doc/2?routing=user1&stored_fields=tags,counter
The result of the above get operation is:
{ "_index": "twitter", "_type": "_doc", "_id": "2", "_version": 1, "_routing": "user1", "found": true, "fields": { "tags": [ "white" ] } }
Also only leaf fields can be returned via the stored_field
option. So object fields can’t be returned and such requests
will fail.
Getting the _source
directly
editUse the /{index}/{type}/{id}/_source
endpoint to get
just the _source
field of the document,
without any additional content around it. For example:
GET twitter/_doc/1/_source
You can also use the same source filtering parameters to control which parts of the _source
will be returned:
GET twitter/_doc/1/_source?_source_include=*.id&_source_exclude=entities'
Note, there is also a HEAD variant for the _source endpoint to efficiently test for document _source existence. An existing document will not have a _source if it is disabled in the mapping.
HEAD twitter/_doc/1/_source
Routing
editWhen indexing using the ability to control the routing, in order to get a document, the routing value should also be provided. For example:
GET twitter/_doc/2?routing=user1
The above will get a tweet with id 2
, but will be routed based on the
user. Note, issuing a get without the correct routing, will cause the
document not to be fetched.
Preference
editControls 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.
Refresh
editThe 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).
Distributed
editThe 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.
Versioning support
editYou can use the version
parameter to retrieve the document only if
its current version is equal to the specified one. This behavior is the same
for all version types with the exception of version type FORCE
which always
retrieves the document. Note that FORCE
version type is deprecated.
Internally, Elasticsearch has marked the old document as deleted and added an entirely new document. The old version of the document doesn’t disappear immediately, although you won’t be able to access it. Elasticsearch cleans up deleted documents in the background as you continue to index more data.