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Get document

Introduced 1.0

After adding a JSON document to your index, you can use the Get Document API operation to retrieve the document’s information and data.

Path and HTTP methods

Use the GET method to retrieve a document and its source or stored fields from a particular index. Use the HEAD method to verify that a document exists:

GET <index>/_doc/<_id>
HEAD <index>/_doc/<_id>

Use _source to retrieve the document source or to verify that it exists:

GET <index>/_source/<_id>
HEAD <index>/_source/<_id>

Query parameters

All query parameters are optional.

Real time

The OpenSearch Get Document API operates in real time by default, which means that it retrieves the latest version of the document regardless of the index’s refresh rate or the rate at which new data becomes searchable. However, if you request stored fields (using the stored_fields parameter) for a document that has been updated but not yet refreshed, then the Get Document API parses and analyzes the document’s source to extract those stored fields.

To disable the real-time behavior and retrieve the document based on the last refreshed state of the index, set the realtime parameter to false.

Source filtering

By default, the Get Document API returns the entire contents of the _source field for the requested document. However, you can choose to exclude the _source field from the response by using the _source URL parameter and setting it to false, as shown in the following example:

GET test-index/_doc/0?_source=false

source includes and excludes

If you only want to retrieve specific fields from the source, use the _source_includes or _source_excludes parameters to include or exclude particular fields, respectively. This can be beneficial for large documents because retrieving only the required fields can reduce network overhead.

Both parameters accept a comma-separated list of fields and wildcard expressions, as shown in the following example, where any _source that contains *.play is included in the response but sources with the field entities are excluded:

GET test-index/_doc/0?_source_includes=*.play&_source_excludes=entities

Shorter notation

If you only want to include certain fields and don’t need to exclude any, you can use a shorter notation by specifying the desired fields directly in the _source parameter:

GET test-index/_doc/0?_source=*.id

Routing

When indexing documents in OpenSearch, you can specify a routing value to control the shard assignments for documents. If routing was used during indexing, you must provide the same routing value when retrieving the document using the Get Document API, as shown in the following example:

GET test-index/_doc/1?routing=user1

This request retrieves the document with the ID 1, but it uses the routing value “user1” to determine on which shard the document is stored. If the correct routing value is not specified, the Get Document API is not able to locate and fetch the requested document.

Preference

The Get Document API allows you to control which shard replica handles the request. By default, the operation is randomly distributed across the available shard replicas.

However, you can specify a preference to influence the replica selection. The preference can be set to one of the following values:

• _local: The operation attempts to execute on a locally allocated shard replica, if possible. This can improve performance by reducing network overhead.
• Custom (string) value: Specifying a custom string value ensures that requests with the same value are routed to the same set of shards. This consistency can be beneficial when managing shards in different refresh states because it prevents “jumping values” that may occur when hitting shards with varying data visibility. A common practice is to use a web session ID or a user name as the custom value.

Refresh

Set the refresh parameter to true to force a refresh of the relevant shard before running the Get Document API operation. This ensures that the most recent data changes are made searchable and visible to the API. However, a refresh should be performed judiciously because it can potentially impose a heavy load on the system and slow down indexing performance. It’s recommended to carefully evaluate the trade-off between data freshness and system load before enabling the refresh parameter.

Distributed

When running the Get Document API, OpenSearch first calculates a hash value based on the document ID, which determines the specific ID of the shard on which the document resides. The operation is then redirected to one of the replicas (including the primary shard and its replica shards) in that shard ID group, and the result is returned from that replica.

A higher number of shard replicas improves the scalability and performance of GET operations because the load can be distributed across multiple replica shards. This means that as the number of replicas increases, you can achieve better scaling and throughput for Get Document API requests.

Versioning support

Use the version parameter to retrieve a document only if its current version matches the specified version number. This can be useful for ensuring data consistency and preventing conflicts when working with versioned documents.

Internally, when a document is updated in OpenSearch, the original version is marked as deleted, and a new version of the document is added. However, the original version doesn’t immediately disappear from the system. While you won’t be able to access it through the Get Document API, OpenSearch manages the cleanup of deleted document versions in the background as you continue indexing new data.

Example request

The following example request retrieves information about a document named 1:

GET sample-index1/_doc/1

Example response

{
  "_index": "sample-index1",
  "_id": "1",
  "_version": 1,
  "_seq_no": 0,
  "_primary_term": 9,
  "found": true,
  "_source": {
    "text": "This is just some sample text."
  }
}

Response body fields