[[docs-delete-by-query]]
=== Delete by query API
++++
<titleabbrev>Delete by query</titleabbrev>
++++

Deletes documents that match the specified query.

[source,console]
--------------------------------------------------
POST /twitter/_delete_by_query
{
  "query": {
    "match": {
      "message": "some message"
    }
  }
}
--------------------------------------------------
// TEST[setup:big_twitter]

////

[source,console-result]
--------------------------------------------------
{
  "took" : 147,
  "timed_out": false,
  "deleted": 119,
  "batches": 1,
  "version_conflicts": 0,
  "noops": 0,
  "retries": {
    "bulk": 0,
    "search": 0
  },
  "throttled_millis": 0,
  "requests_per_second": -1.0,
  "throttled_until_millis": 0,
  "total": 119,
  "failures" : [ ]
}
--------------------------------------------------
// TESTRESPONSE[s/"took" : 147/"took" : "$body.took"/]
////

[[docs-delete-by-query-api-request]]
==== {api-request-title}

`POST /<target>/_delete_by_query`

[[docs-delete-by-query-api-desc]]
==== {api-description-title}

You can specify the query criteria in the request URI or the request body
using the same syntax as the  <<search-search,Search API>>. 

When you submit a delete by query request, {es} gets a snapshot of the data stream or index
when it begins processing the request and deletes matching documents using
`internal` versioning. If a document changes between the time that the
snapshot is taken and the delete operation is processed, it results in a version
conflict and the delete operation fails. 

NOTE: Documents with a version equal to 0 cannot be deleted using delete by
query because `internal` versioning does not support 0 as a valid
version number.

While processing a delete by query request, {es} performs multiple search
requests sequentially to find all of the matching documents to delete. A bulk
delete request is performed for each batch of matching documents. If a
search or bulk request is rejected, the requests are retried up to 10 times, with
exponential back off. If the maximum retry limit is reached, processing halts
and all failed requests are returned in the response. Any delete requests that 
completed successfully still stick, they are not rolled back. 

You can opt to count version conflicts instead of halting and returning by 
setting `conflicts` to `proceed`. 

===== Refreshing shards

Specifying the `refresh` parameter refreshes all shards involved in the delete
by query once the request completes. This is different than the delete API's 
`refresh` parameter, which causes just the shard that received the delete 
request to be refreshed. Unlike the delete API, it does not support 
`wait_for`.

[[docs-delete-by-query-task-api]]
===== Running delete by query asynchronously

If the request contains `wait_for_completion=false`, {es}
performs some preflight checks, launches the request, and returns a
<<tasks,`task`>> you can use to cancel or get the status of the task. {es} creates a
record of this task as a document at `.tasks/task/${taskId}`. When you are 
done with a task, you should delete the task document so {es} can reclaim the
space.

===== Waiting for active shards

`wait_for_active_shards` controls how many copies of a shard must be active
before proceeding with the request. See <<index-wait-for-active-shards>>
for details. `timeout` controls how long each write request waits for unavailable
shards to become available. Both work exactly the way they work in the
<<docs-bulk,Bulk API>>. Delete by query uses scrolled searches, so you can also
specify the `scroll` parameter to control how long it keeps the search context 
alive, for example `?scroll=10m`. The default is 5 minutes.

===== Throttling delete requests

To control the rate at which delete by query issues batches of delete operations,
you can set `requests_per_second` to any positive decimal number. This pads each
batch with a wait time to throttle the rate. Set `requests_per_second` to `-1` 
to disable throttling.

Throttling uses a wait time between batches so that the internal scroll requests 
can be given a timeout that takes the request padding into account. The padding 
time is the difference between the batch size divided by the 
`requests_per_second` and the time spent writing.  By default the batch size is 
`1000`, so if `requests_per_second` is set to `500`:

[source,txt]
--------------------------------------------------
target_time = 1000 / 500 per second = 2 seconds
wait_time = target_time - write_time = 2 seconds - .5 seconds = 1.5 seconds
--------------------------------------------------

Since the batch is issued as a single `_bulk` request, large batch sizes 
cause {es} to create many requests and wait before starting the next set. 
This is "bursty" instead of "smooth". 

[[docs-delete-by-query-slice]]
===== Slicing

Delete by query supports <<sliced-scroll, sliced scroll>> to parallelize the
delete process. This can improve efficiency and provide a
convenient way to break the request down into smaller parts.

Setting `slices` to `auto` chooses a reasonable number for most data streams and indices. 
If you're slicing manually or otherwise tuning automatic slicing, keep in mind 
that:

* Query performance is most efficient when the number of `slices` is equal to 
the number of shards in the index or backing index. If that number is large (for example,
500), choose a lower number as too many `slices` hurts performance. Setting
`slices` higher than the number of shards generally does not improve efficiency
and adds overhead.

* Delete performance scales linearly across available resources with the
number of slices.

Whether query or delete performance dominates the runtime depends on the
documents being reindexed and cluster resources.

[[docs-delete-by-query-api-path-params]]
==== {api-path-parms-title}

`<target>`::
(Optional, string)
Comma-separated list of data streams, indices, and index aliases to search.
Wildcard (`*`) expressions are supported.
+
To search all data streams or indices in a cluster, omit this parameter or use
`_all` or `*`.

[[docs-delete-by-query-api-query-params]]
==== {api-query-parms-title}

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=allow-no-indices]
+
Defaults to `true`.

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=analyzer]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=analyze_wildcard]
  
`conflicts`::
  (Optional, string) What to do if delete by query hits version conflicts: 
  `abort` or `proceed`. Defaults to `abort`.

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=default_operator]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=df]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=expand-wildcards]
+
Defaults to `open`.

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=from]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=index-ignore-unavailable]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=lenient]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=max_docs]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=preference]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=search-q]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=request_cache]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=refresh]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=requests_per_second]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=routing]

`scroll`::
(Optional, <<time-units,time value>>)
Period to retain the <<scroll-search-context,search context>> for scrolling. See
<<request-body-search-scroll>>.

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=scroll_size]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=search_type]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=search_timeout]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=slices]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=sort]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source_excludes]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=source_includes]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=stats]
  
include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=terminate_after]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=timeout]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=version]

include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=wait_for_active_shards]

[[docs-delete-by-query-api-request-body]]
==== {api-request-body-title}

`query`::
  (Optional, <<query-dsl,query object>>) Specifies the documents to delete 
  using the  <<query-dsl,Query DSL>>.
  

[[docs-delete-by-query-api-response-body]]
==== Response body

//////////////////////////

[source,console]
--------------------------------------------------
POST /twitter/_delete_by_query
{
  "query": { <1>
    "match": {
      "message": "some message"
    }
  }
}
--------------------------------------------------
// TEST[setup:big_twitter]

//////////////////////////

The JSON response looks like this:

[source,console-result]
--------------------------------------------------
{
  "took" : 147,
  "timed_out": false,
  "total": 119,
  "deleted": 119,
  "batches": 1,
  "version_conflicts": 0,
  "noops": 0,
  "retries": {
    "bulk": 0,
    "search": 0
  },
  "throttled_millis": 0,
  "requests_per_second": -1.0,
  "throttled_until_millis": 0,
  "failures" : [ ]
}
--------------------------------------------------
// TESTRESPONSE[s/: [0-9]+/: $body.$_path/]

`took`::

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

`timed_out`::

This flag is set to `true` if any of the requests executed during the
delete by query execution has timed out.

`total`::

The number of documents that were successfully processed.

`deleted`::

The number of documents that were successfully deleted.

`batches`::

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

`version_conflicts`::

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

`noops`::

This field is always equal to zero for delete by query. It only exists
so that delete by query, update by query, and reindex APIs return responses
 with the same structure.

`retries`::

The number of retries attempted by delete by query. `bulk` is the number
of bulk actions retried, and `search` is the number of search actions retried.

`throttled_millis`::

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

`requests_per_second`::

The number of requests per second effectively executed during the delete by query.

`throttled_until_millis`::

This field should always be equal to zero in a `_delete_by_query` response. It only
has meaning when using the <<tasks, Task API>>, where it
indicates the next time (in milliseconds since epoch) a throttled request will be
executed again in order to conform to `requests_per_second`.

`failures`::

Array of failures if there were any unrecoverable errors during the process. If
this is non-empty then the request aborted because of those failures.
Delete by query is implemented using batches, and any failure causes the entire
process to abort but all failures in the current batch are collected into the
array. You can use the `conflicts` option to prevent reindex from aborting on
version conflicts.  

[[docs-delete-by-query-api-example]]
==== {api-examples-title}

Delete all tweets from the `twitter` data stream or index:

[source,console]
--------------------------------------------------
POST twitter/_delete_by_query?conflicts=proceed
{
  "query": {
    "match_all": {}
  }
}
--------------------------------------------------
// TEST[setup:twitter]

Delete documents from multiple data streams or indices:

[source,console]
--------------------------------------------------
POST /twitter,blog/_delete_by_query
{
  "query": {
    "match_all": {}
  }
}
--------------------------------------------------
// TEST[s/^/PUT twitter\nPUT blog\n/]

Limit the delete by query operation to shards that a particular routing
value: 

[source,console]
--------------------------------------------------
POST twitter/_delete_by_query?routing=1
{
  "query": {
    "range" : {
        "age" : {
           "gte" : 10
        }
    }
  }
}
--------------------------------------------------
// TEST[setup:twitter]

By default `_delete_by_query` uses scroll batches of 1000. You can change the
batch size with the `scroll_size` URL parameter:

[source,console]
--------------------------------------------------
POST twitter/_delete_by_query?scroll_size=5000
{
  "query": {
    "term": {
      "user": "kimchy"
    }
  }
}
--------------------------------------------------
// TEST[setup:twitter]

[discrete]
[[docs-delete-by-query-manual-slice]]
===== Slice manually

Slice a delete by query manually by providing a slice id and total number of
slices:

[source,console]
----------------------------------------------------------------
POST twitter/_delete_by_query
{
  "slice": {
    "id": 0,
    "max": 2
  },
  "query": {
    "range": {
      "likes": {
        "lt": 10
      }
    }
  }
}
POST twitter/_delete_by_query
{
  "slice": {
    "id": 1,
    "max": 2
  },
  "query": {
    "range": {
      "likes": {
        "lt": 10
      }
    }
  }
}
----------------------------------------------------------------
// TEST[setup:big_twitter]

Which you can verify works with:

[source,console]
----------------------------------------------------------------
GET _refresh
POST twitter/_search?size=0&filter_path=hits.total
{
  "query": {
    "range": {
      "likes": {
        "lt": 10
      }
    }
  }
}
----------------------------------------------------------------
// TEST[continued]

Which results in a sensible `total` like this one:

[source,console-result]
----------------------------------------------------------------
{
  "hits": {
    "total" : {
        "value": 0,
        "relation": "eq"
    }
  }
}
----------------------------------------------------------------

[discrete]
[[docs-delete-by-query-automatic-slice]]
===== Use automatic slicing

You can also let delete-by-query automatically parallelize using
<<sliced-scroll, sliced scroll>> to slice on `_id`. Use `slices` to specify
the number of slices to use:

[source,console]
----------------------------------------------------------------
POST twitter/_delete_by_query?refresh&slices=5
{
  "query": {
    "range": {
      "likes": {
        "lt": 10
      }
    }
  }
}
----------------------------------------------------------------
// TEST[setup:big_twitter]

Which you also can verify works with:

[source,console]
----------------------------------------------------------------
POST twitter/_search?size=0&filter_path=hits.total
{
  "query": {
    "range": {
      "likes": {
        "lt": 10
      }
    }
  }
}
----------------------------------------------------------------
// TEST[continued]

Which results in a sensible `total` like this one:

[source,console-result]
----------------------------------------------------------------
{
  "hits": {
    "total" : {
        "value": 0,
        "relation": "eq"
    }
  }
}
----------------------------------------------------------------

Setting `slices` to `auto` will let {es} choose the number of slices
to use. This setting will use one slice per shard, up to a certain limit. If
there are multiple source data streams or indices, it will choose the number of slices based
on the index or backing index with the smallest number of shards.

Adding `slices` to `_delete_by_query` just automates the manual process used in
the section above, creating sub-requests which means it has some quirks:

* You can see these requests in the
<<tasks,Tasks APIs>>. These sub-requests are "child"
tasks of the task for the request with `slices`.
* Fetching the status of the task for the request with `slices` only contains
the status of completed slices.
* These sub-requests are individually addressable for things like cancellation
and rethrottling.
* Rethrottling the request with `slices` will rethrottle the unfinished
sub-request proportionally.
* Canceling the request with `slices` will cancel each sub-request.
* Due to the nature of `slices` each sub-request won't get a perfectly even
portion of the documents. All documents will be addressed, but some slices may
be larger than others. Expect larger slices to have a more even distribution.
* Parameters like `requests_per_second` and `max_docs` on a request with
slices` are distributed proportionally to each sub-request. Combine that with
the point above about distribution being uneven and you should conclude that
using `max_docs` with `slices` might not result in exactly `max_docs` documents
being deleted.
* Each sub-request gets a slightly different snapshot of the source data stream or index
though these are all taken at approximately the same time.

[discrete]
[[docs-delete-by-query-rethrottle]]
===== Change throttling for a request

The value of `requests_per_second` can be changed on a running delete by query
using the `_rethrottle` API. Rethrottling that speeds up the
query takes effect immediately but rethrotting that slows down the query 
takes effect after completing the current batch to prevent scroll
timeouts.

[source,console]
--------------------------------------------------
POST _delete_by_query/r1A2WoRbTwKZ516z6NEs5A:36619/_rethrottle?requests_per_second=-1
--------------------------------------------------

Use the <<tasks,tasks API>> to get the task ID. Set `requests_per_second`
to any positive decimal value or `-1` to disable throttling.

===== Get the status of a delete by query operation

Use the <<tasks,tasks API>> to get the status of a delete by query
operation:


[source,console]
--------------------------------------------------
GET _tasks?detailed=true&actions=*/delete/byquery
--------------------------------------------------
// TEST[skip:No tasks to retrieve]

The response looks like:

[source,console-result]
--------------------------------------------------
{
  "nodes" : {
    "r1A2WoRbTwKZ516z6NEs5A" : {
      "name" : "r1A2WoR",
      "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/delete/byquery",
          "status" : {    <1>
            "total" : 6154,
            "updated" : 0,
            "created" : 0,
            "deleted" : 3500,
            "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.

With the task id you can look up the task directly:

[source,console]
--------------------------------------------------
GET /_tasks/r1A2WoRbTwKZ516z6NEs5A:36619
--------------------------------------------------
// TEST[catch:missing]

The advantage of this API is that it integrates with `wait_for_completion=false`
to transparently return the status of completed tasks. If the task is completed
and `wait_for_completion=false` was set on it then it'll come back with
`results` or an `error` field. The cost of this feature is the document that
`wait_for_completion=false` creates at `.tasks/task/${taskId}`. It is up to
you to delete that document.


[discrete]
[[docs-delete-by-query-cancel-task-api]]
===== Cancel a delete by query operation

Any delete by query can be canceled using the <<tasks,task cancel API>>:

[source,console]
--------------------------------------------------
POST _tasks/r1A2WoRbTwKZ516z6NEs5A:36619/_cancel
--------------------------------------------------

The task ID can be found using the <<tasks,tasks API>>.

Cancellation should happen quickly but might take a few seconds. The task status 
API above will continue to list the delete by query task until this task checks that it 
has been cancelled and terminates itself.
