[[use-a-data-stream]]
== Use a data stream

After you <<set-up-a-data-stream,set up a data stream>>, you can do
the following:

* <<add-documents-to-a-data-stream>>
* <<search-a-data-stream>>
* <<manually-roll-over-a-data-stream>>
* <<reindex-with-a-data-stream>>

////
[source,console]
----
PUT /_index_template/logs_data_stream
{
  "index_patterns": [ "logs*" ],
  "data_stream": {
    "timestamp_field": "@timestamp"
  },
  "template": {
    "mappings": {
      "properties": {
        "@timestamp": {
          "type": "date"
        }
      }
    }
  }
}

PUT /_data_stream/logs
----
////

[discrete]
[[add-documents-to-a-data-stream]]
=== Add documents to a data stream

You can add documents to a data stream using the following requests:

* An <<docs-index_,index API>> request with an
<<docs-index-api-op_type,`op_type`>> set to `create`. Specify the data
stream's name in place of an index name.
+
--
NOTE: The `op_type` parameter defaults to `create` when adding new documents.

.*Example: Index API request*
[%collapsible]
====
The following <<docs-index_,index API>> adds a new document to the `logs` data
stream.

[source,console]
----
POST /logs/_doc/
{
  "@timestamp": "2020-12-07T11:06:07.000Z",
  "user": {
    "id": "8a4f500d"
  },
  "message": "Login successful"
}
----
// TEST[continued]
====
--

* A <<docs-bulk,bulk API>> request using the `create` action. Specify the data
stream's name in place of an index name.
+
--
NOTE: Data streams do not support other bulk actions, such as `index`.

.*Example: Bulk API request*
[%collapsible]
====
The following <<docs-bulk,bulk API>> index request adds several new documents to
the `logs` data stream. Note that only the `create` action is used.

[source,console]
----
PUT /logs/_bulk?refresh
{"create":{"_index" : "logs"}}
{ "@timestamp": "2020-12-08T11:04:05.000Z", "user": { "id": "vlb44hny" }, "message": "Login attempt failed" }
{"create":{"_index" : "logs"}}
{ "@timestamp": "2020-12-08T11:06:07.000Z", "user": { "id": "8a4f500d" }, "message": "Login successful" }
{"create":{"_index" : "logs"}}
{ "@timestamp": "2020-12-09T11:07:08.000Z", "user": { "id": "l7gk7f82" }, "message": "Logout successful" }
----
// TEST[continued]
====
--

[discrete]
[[search-a-data-stream]]
=== Search a data stream

The following search APIs support data streams:

* <<search-search, Search>>
* <<async-search, Async search>>
* <<search-multi-search, Multi search>>
* <<search-field-caps, Field capabilities>>
////
* <<eql-search-api, EQL search>>
////

.*Example*
[%collapsible]
====
The following <<search-search,search API>> request searches the `logs` data
stream for documents with a timestamp between today and yesterday that also have
`message` value of `login successful`.

[source,console]
----
GET /logs/_search
{
  "query": {
    "bool": {
      "must": {
        "range": {
          "@timestamp": {
            "gte": "now-1d/d",
            "lt": "now/d"
          }
        }
      },
      "should": {
        "match": {
          "message": "login successful"
        }
      }
    }
  }
}
----
// TEST[continued]
====

[discrete]
[[manually-roll-over-a-data-stream]]
=== Manually roll over a data stream

A rollover creates a new backing index for a data stream. This new backing index
becomes the stream's <<data-stream-write-index,write index>> and increments
the stream's <<data-streams-generation,generation>>.

In most cases, we recommend using <<index-lifecycle-management,{ilm-init}>> to
automate rollovers for data streams. This lets you automatically roll over the
current write index when it meets specified criteria, such as a maximum age or
size.

However, you can also use the <<indices-rollover-index,rollover API>> to
manually perform a rollover. This can be useful if you want to
<<data-streams-change-mappings-and-settings,apply mapping or setting changes>>
to the stream's write index after updating a data stream's template.

.*Example*
[%collapsible]
====
The following <<indices-rollover-index,rollover API>> request submits a manual
rollover request for the `logs` data stream.

[source,console]
----
POST /logs/_rollover/
{
  "conditions": {
    "max_docs":   "1"
  }
}
----
// TEST[continued]
====

[discrete]
[[reindex-with-a-data-stream]]
=== Reindex with a data stream

You can use the <<docs-reindex,reindex API>> to copy documents to a data stream
from an existing index, index alias, or data stream.

A reindex copies documents from a _source_ to a _destination_. The source and
destination can be any pre-existing index, index alias, or data stream. However,
the source and destination must be different. You cannot reindex a data stream
into itself.

Because data streams are <<data-streams-append-only,append-only>>, a reindex
request to a data stream destination must have an `op_type` of `create`. This
means a reindex can only add new documents to a data stream. It cannot update
existing documents in the data stream destination.

A reindex can be used to:

* Convert an existing index alias and collection of time-based indices into a
  data stream.

* Apply a new or updated <<create-a-data-stream-template,composable template>>
  by reindexing an existing data stream into a new one. This applies mapping
  and setting changes in the template to each document and backing index of the
  data stream destination. See
  <<data-streams-use-reindex-to-change-mappings-settings>>.

TIP: If you only want to update the mappings or settings of a data stream's
write index, we recommend you update the <<create-a-data-stream-template,data
stream's template>> and perform a <<manually-roll-over-a-data-stream,rollover>>.

.*Example*
[%collapsible]
====
The following reindex request copies documents from the `archive` index alias to
the existing `logs` data stream. Because the destination is a data stream, the
request's `op_type` is `create`.

////
[source,console]
----
PUT /_bulk?refresh=wait_for
{"create":{"_index" : "archive_1"}}
{ "@timestamp": "2020-12-08T11:04:05.000Z" }
{"create":{"_index" : "archive_2"}}
{ "@timestamp": "2020-12-08T11:06:07.000Z" }
{"create":{"_index" : "archive_2"}}
{ "@timestamp": "2020-12-09T11:07:08.000Z" }
{"create":{"_index" : "archive_2"}}
{ "@timestamp": "2020-12-09T11:07:08.000Z" }

POST /_aliases
{
  "actions" : [
    { "add" : { "index" : "archive_1", "alias" : "archive" } },
    { "add" : { "index" : "archive_2", "alias" : "archive", "is_write_index" : true} }
  ]
}
----
// TEST[continued]
////

[source,console]
----
POST /_reindex
{
  "source": {
    "index": "archive"
  },
  "dest": {
    "index": "logs",
    "op_type": "create"
  }
}
----
// TEST[continued]
====

You can also reindex documents from a data stream to an index, index
alias, or data stream.

.*Example*
[%collapsible]
====
The following reindex request copies documents from the `logs` data stream
to the existing `archive` index alias. Because the destination is not a data
stream, the `op_type` does not need to be specified.

[source,console]
----
POST /_reindex
{
  "source": {
    "index": "logs"
  },
  "dest": {
    "index": "archive"
  }
}
----
// TEST[continued]
====

////
[source,console]
----
DELETE /_data_stream/logs

DELETE /_index_template/logs_data_stream
----
// TEST[continued]
////