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

The simplest usage of `updateByQuery` updates each
document in an index without changing the source. This usage enables
picking up a new property or another online mapping change.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query]
--------------------------------------------------

Calls to the `updateByQuery` API start by getting a snapshot of the index, indexing
any documents found using the `internal` versioning.

NOTE: Version conflicts happen when a document changes between the time of the
snapshot and the time the index request processes.

When the versions match, `updateByQuery` updates the document
and increments the version number.

All update and query failures cause `updateByQuery` to abort. These failures are
available from the `BulkByScrollResponse#getIndexingFailures` method. Any
successful updates remain and are not rolled back. While the first failure
causes the abort, the response contains all of the failures generated by the
failed bulk request.

To prevent version conflicts from causing `updateByQuery` to abort, set
`abortOnVersionConflict(false)`. The first example does this because it is
trying to pick up an online mapping change and a version conflict means that
the conflicting document was updated between the start of the `updateByQuery`
and the time when it attempted to update the document. This is fine because
that update will have picked up the online mapping update.

The `UpdateByQueryRequestBuilder` API supports filtering the updated documents,
limiting the total number of documents to update, and updating documents
with a script:


["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-filter]
--------------------------------------------------

`UpdateByQueryRequestBuilder` also enables direct access to the query used
to select the documents. You can use this access to change the default scroll size or
otherwise modify the request for matching documents.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-size]
--------------------------------------------------

You can also combine `maxDocs` with sorting to limit the documents updated:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-sort]
--------------------------------------------------

In addition to changing the `_source` field for the document, you can use a
script to change the action, similar to the Update API:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-script]
--------------------------------------------------

As in the <<java-docs-update,Update API>>, you can set the value of `ctx.op` to change the
operation that executes:

`noop`::

Set `ctx.op = "noop"` if your script doesn't make any
changes. The `updateByQuery` operation then omits that document from the updates.
This behavior increments the `noop` counter in the response body.

`delete`::

Set `ctx.op = "delete"` if your script decides that the document must be
deleted. The deletion will be reported in the `deleted` counter in the
response body.

Setting `ctx.op` to any other value generates an error. Setting any
other field in `ctx` generates an error.

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.

You can also perform these operations on multiple indices at once, similar to the search API:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-multi-index]
--------------------------------------------------

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

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-routing]
--------------------------------------------------

`updateByQuery` can also use the ingest node by
specifying a `pipeline` like this:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-pipeline]
--------------------------------------------------

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

You can fetch the status of all running update-by-query requests with the Task API:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-list-tasks]
--------------------------------------------------

With the `TaskId` shown above you can look up the task directly:

// provide API Example
["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-get-task]
--------------------------------------------------

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

Any Update By Query can be canceled using the Task Cancel API:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-cancel-task]
--------------------------------------------------

Use the `list tasks` API to find the value of `taskId`.

Cancelling a request is typically a very fast process but can take up to a few seconds.
The task status API continues to list the task until the cancellation is complete.

[discrete]
[[java-docs-update-by-query-rethrottle]]
=== Rethrottling

Use the `_rethrottle` API to change the value of `requests_per_second` on a running update:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{client-reindex-tests}/ReindexDocumentationIT.java[update-by-query-rethrottle]
--------------------------------------------------

Use the `list tasks` API to find the value of `taskId`.

As with the `updateByQuery` API, the value of `requests_per_second`
can be any positive float value to set the level of the throttle, or `Float.POSITIVE_INFINITY` to disable throttling.
A value of `requests_per_second` that speeds up the process takes
effect immediately. `requests_per_second` values that slow the query take effect
after completing the current batch in order to prevent scroll timeouts.
