[[docs-update-by-query]]
== Update By Query API

experimental[The update-by-query API is new and should still be considered experimental.  The API may change in ways that are not backwards compatible]

The simplest usage of `_update_by_query` just performs an update on every
document in the index without changing the source. This is useful to
<<picking-up-a-new-property,pick up a new property>> or some other online
mapping change. Here is the API:

[source,js]
--------------------------------------------------
POST twitter/_update_by_query?conflicts=proceed
--------------------------------------------------
// CONSOLE
// TEST[setup:big_twitter]

That will return something like this:

[source,js]
--------------------------------------------------
{
  "took" : 147,
  "timed_out": false,
  "updated": 120,
  "batches": 2,
  "version_conflicts": 0,
  "noops": 0,
  "retries": 0,
  "throttled_millis": 0,
  "requests_per_second": "unlimited",
  "throttled_until_millis": 0,
  "total": 120,
  "failures" : [ ]
}
--------------------------------------------------
// TESTRESPONSE[s/"took" : 147/"took" : "$body.took"/]

`_update_by_query` gets a snapshot of the index when it starts and indexes what
it finds using `internal` versioning. That means that you'll get a version
conflict if the document changes between the time when the snapshot was taken
and when the index request is processed. When the versions match the document
is updated and the version number is incremented.

All update and query failures cause the `_update_by_query` to abort and are
returned in the `failures` of the response. The updates that have been
performed still stick. In other words, the process is not rolled back, only
aborted. While the first failure causes the abort all failures that are
returned by the failing bulk request are returned in the `failures` element so
it's possible for there to be quite a few.

If you want to simply count version conflicts not cause the `_update_by_query`
to abort you can set `conflicts=proceed` on the url or `"conflicts": "proceed"`
in the request body. The first example does this because it is just trying to
pick up an online mapping change and a version conflict simply means that the
conflicting document was updated between the start of the `_update_by_query`
and the time when it attempted to update the document. This is fine because
that update will have picked up the online mapping update.

Back to the API format, you can limit `_update_by_query` to a single type. This
will only update `tweet`s from the `twitter` index:

[source,js]
--------------------------------------------------
POST twitter/tweet/_update_by_query?conflicts=proceed
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

You can also limit `_update_by_query` using the
<<query-dsl,Query DSL>>. This will update all documents from the
`twitter` index for the user `kimchy`:

[source,js]
--------------------------------------------------
POST twitter/_update_by_query?conflicts=proceed
{
  "query": { <1>
    "term": {
      "user": "kimchy"
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

<1> The query must be passed as a value to the `query` key, in the same
way as the <<search-search,Search API>>. You can also use the `q`
parameter in the same way as the search api.

So far we've only been updating documents without changing their source. That
is genuinely useful for things like
<<picking-up-a-new-property,picking up new properties>> but it's only half the
fun. `_update_by_query` supports a `script` object to update the document. This
will increment the `likes` field on all of kimchy's tweets:

[source,js]
--------------------------------------------------
POST twitter/_update_by_query
{
  "script": {
    "inline": "ctx._source.likes++"
  },
  "query": {
    "term": {
      "user": "kimchy"
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

Just as in <<docs-update,Update API>> you can set `ctx.op = "noop"` if
your script decides that it doesn't have to make any changes. That will cause
`_update_by_query` to omit that document from its updates. Setting `ctx.op` to
anything else is an error. If you want to delete by a query you can use the
{plugins}/plugins-delete-by-query.html[Delete by Query plugin] instead. Setting any
other field in `ctx` is an error.

Note that we stopped specifying `conflicts=proceed`. In this case we want a
version conflict to abort the process so we can handle the failure.

This API doesn't allow you to move the documents it touches, just modify their
source. This is intentional! We've made no provisions for removing the document
from its original location.

It's also possible to do this whole thing on multiple indexes and multiple
types at once, just like the search API:

[source,js]
--------------------------------------------------
POST twitter,blog/tweet,post/_update_by_query
--------------------------------------------------
// CONSOLE
// TEST[s/^/PUT twitter\nPUT blog\n/]

If you provide `routing` then the routing is copied to the scroll query,
limiting the process to the shards that match that routing value:

[source,js]
--------------------------------------------------
POST twitter/_update_by_query?routing=1
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

By default `_update_by_query` uses scroll batches of 100. You can change the
batch size with the `scroll_size` URL parameter:

[source,js]
--------------------------------------------------
POST twitter/_update_by_query?scroll_size=1000
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

`_update_by_query` can also use the <<ingest>> feature by
specifying a `pipeline` like this:

[source,js]
--------------------------------------------------
PUT _ingest/pipeline/set-foo
{
  "description" : "sets foo",
  "processors" : [ {
      "set" : {
        "field": "foo",
        "value": "bar"
      }
  } ]
}
POST twitter/_update_by_query?pipeline=set-foo
--------------------------------------------------
// CONSOLE
// TEST[setup:twitter]

[float]
=== URL Parameters

In addition to the standard parameters like `pretty`, the Update By Query API
also supports `refresh`, `wait_for_completion`, `consistency`, and `timeout`.

Sending the `refresh` will update all shards in the index being updated when
the request completes. This is different than the Index API's `refresh`
parameter which causes just the shard that received the new data to be indexed.

If the request contains `wait_for_completion=false` then Elasticsearch will
perform some preflight checks, launch the request, and then return a `task`
which can be used with <<docs-update-by-query-task-api,Tasks APIs>> to cancel
or get the status of the task. For now, once the request is finished the task
is gone and the only place to look for the ultimate result of the task is in
the Elasticsearch log file. This will be fixed soon.

`consistency` controls how many copies of a shard must respond to each write
request. `timeout` controls how long each write request waits for unavailable
shards to become available. Both work exactly how they work in the
<<docs-bulk,Bulk API>>.

`requests_per_second` can be set to any decimal number (`1.4`, `6`, `1000`, etc)
and throttles the number of requests per second that the update by query issues.
The throttling is done waiting between bulk batches so that it can manipulate
the scroll timeout. The wait time is the difference between the time it took the
batch to complete and the time `requests_per_second * requests_in_the_batch`.
Since the batch isn't broken into multiple bulk requests large batch sizes will
cause Elasticsearch to create many requests and then wait for a while before
starting the next set. This is "bursty" instead of "smooth". The default is
`unlimited` which is also the only non-number value that it accepts.

[float]
=== Response body

The JSON response looks like this:

[source,js]
--------------------------------------------------
{
  "took" : 639,
  "updated": 0,
  "batches": 1,
  "version_conflicts": 2,
  "retries": 0,
  "throttled_millis": 0,
  "failures" : [ ]
}
--------------------------------------------------

`took`::

The number of milliseconds from start to end of the whole operation.

`updated`::

The number of documents that were successfully updated.

`batches`::

The number of scroll responses pulled back by the the update by query.

`version_conflicts`::

The number of version conflicts that the update by query hit.

`retries`::

The number of retries that the update by query did in response to a full queue.

`throttled_millis`::

Number of milliseconds the request slept to conform to `requests_per_second`.

`failures`::

Array of all indexing failures. If this is non-empty then the request aborted
because of those failures. See `conflicts` for how to prevent version conflicts
from aborting the operation.


[float]
[[docs-update-by-query-task-api]]
=== Works with the Task API

While Update By Query is running you can fetch their status using the
<<tasks,Task API>>:

[source,js]
--------------------------------------------------
GET _tasks/?pretty&detailed=true&action=*byquery
--------------------------------------------------
// CONSOLE

The responses looks like:

[source,js]
--------------------------------------------------
{
  "nodes" : {
    "r1A2WoRbTwKZ516z6NEs5A" : {
      "name" : "Tyrannus",
      "transport_address" : "127.0.0.1:9300",
      "host" : "127.0.0.1",
      "ip" : "127.0.0.1:9300",
      "attributes" : {
        "testattr" : "test",
        "portsfile" : "true"
      },
      "tasks" : {
        "r1A2WoRbTwKZ516z6NEs5A:36619" : {
          "node" : "r1A2WoRbTwKZ516z6NEs5A",
          "id" : 36619,
          "type" : "transport",
          "action" : "indices:data/write/update/byquery",
          "status" : {    <1>
            "total" : 6154,
            "updated" : 3500,
            "created" : 0,
            "deleted" : 0,
            "batches" : 36,
            "version_conflicts" : 0,
            "noops" : 0,
            "retries": 0,
            "throttled_millis": 0
          },
          "description" : ""
        }
      }
    }
  }
}
--------------------------------------------------

<1> this object contains the actual status. It is just like the response json
with the important addition of the `total` field. `total` is the total number
of operations that the reindex expects to perform. You can estimate the
progress by adding the `updated`, `created`, and `deleted` fields. The request
will finish when their sum is equal to the `total` field.


[float]
[[docs-update-by-query-cancel-task-api]]
=== Works with the Cancel Task API

Any Update By Query can be canceled using the <<tasks,Task Cancel API>>:

[source,js]
--------------------------------------------------
POST _tasks/taskid:1/_cancel
--------------------------------------------------
// CONSOLE

The `task_id` can be found using the tasks API above.

Cancelation should happen quickly but might take a few seconds. The task status
API above will continue to list the task until it is wakes to cancel itself.


[float]
[[docs-update-by-query-rethrottle]]
=== Rethrottling

The value of `requests_per_second` can be changed on a running update by query
using the `_rethrottle` API:

[source,js]
--------------------------------------------------
POST _update_by_query/taskid:1/_rethrottle?requests_per_second=unlimited
--------------------------------------------------
// CONSOLE

The `task_id` can be found using the tasks API above.

Just like when setting it on the `_update_by_query` API `requests_per_second`
can be either `unlimited` to disable throttling or any decimal number like `1.7`
or `12` to throttle to that level. Rethrottling that speeds up the query takes
effect immediately but rethrotting that slows down the query will take effect
on after completing the current batch. This prevents scroll timeouts.


[float]
[[picking-up-a-new-property]]
=== Pick up a new property

Say you created an index without dynamic mapping, filled it with data, and then
added a mapping value to pick up more fields from the data:

[source,js]
--------------------------------------------------
PUT test
{
  "mappings": {
    "test": {
      "dynamic": false,   <1>
      "properties": {
        "text": {"type": "text"}
      }
    }
  }
}

POST test/test?refresh
{
  "text": "words words",
  "flag": "bar"
}
POST test/test?refresh
{
  "text": "words words",
  "flag": "foo"
}
PUT test/_mapping/test   <2>
{
  "properties": {
    "text": {"type": "text"},
    "flag": {"type": "text", "analyzer": "keyword"}
  }
}
--------------------------------------------------
// CONSOLE

<1> This means that new fields won't be indexed, just stored in `_source`.

<2> This updates the mapping to add the new `flag` field. To pick up the new
field you have to reindex all documents with it.

Searching for the data won't find anything:

[source,js]
--------------------------------------------------
POST test/_search?filter_path=hits.total
{
  "query": {
    "match": {
      "flag": "foo"
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[continued]

[source,js]
--------------------------------------------------
{
  "hits" : {
    "total" : 0
  }
}
--------------------------------------------------
// TESTRESPONSE

But you can issue an `_update_by_query` request to pick up the new mapping:

[source,js]
--------------------------------------------------
POST test/_update_by_query?refresh&conflicts=proceed
POST test/_search?filter_path=hits.total
{
  "query": {
    "match": {
      "flag": "foo"
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[continued]

[source,js]
--------------------------------------------------
{
  "hits" : {
    "total" : 1
  }
}
--------------------------------------------------
// TESTRESPONSE

You can do the exact same thing when adding a field to a multifield.
