Update By Query API
editUpdate By Query API
editThe simplest usage of _update_by_query
just performs an update on every
document in the index without changing the source. This is useful to
pick up a new property or some other online
mapping change. Here is the API:
POST twitter/_update_by_query?conflicts=proceed
That will return something like this:
{ "took" : 147, "timed_out": false, "updated": 120, "deleted": 0, "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": 120, "failures" : [ ] }
_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.
Since internal
versioning does not support the value 0 as a valid
version number, documents with version equal to zero cannot be updated using
_update_by_query
and will fail the request.
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; therefore
it’s possible for there to be quite a few failed entities.
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, this will update tweets from the twitter
index:
POST twitter/_doc/_update_by_query?conflicts=proceed
You can also limit _update_by_query
using the
Query DSL. This will update all documents from the
twitter
index for the user kimchy
:
The query must be passed as a value to the |
So far we’ve only been updating documents without changing their source. That
is genuinely useful for things like
picking up new properties but it’s only half the
fun. _update_by_query
supports scripts to update
the document. This will increment the likes
field on all of kimchy’s tweets:
POST twitter/_update_by_query { "script": { "source": "ctx._source.likes++", "lang": "painless" }, "query": { "term": { "user": "kimchy" } } }
Just as in Update API you can set ctx.op
to change the
operation that is executed:
-
noop
-
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. This no operation will be reported in thenoop
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 thedeleted
counter in the response body.
Setting ctx.op
to anything else is an error. 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:
POST twitter,blog/_doc,post/_update_by_query
If you provide routing
then the routing is copied to the scroll query,
limiting the process to the shards that match that routing value:
POST twitter/_update_by_query?routing=1
By default _update_by_query
uses scroll batches of 1000. You can change the
batch size with the scroll_size
URL parameter:
POST twitter/_update_by_query?scroll_size=100
_update_by_query
can also use the Ingest Node feature by
specifying a pipeline
like this:
PUT _ingest/pipeline/set-foo { "description" : "sets foo", "processors" : [ { "set" : { "field": "foo", "value": "bar" } } ] } POST twitter/_update_by_query?pipeline=set-foo
URL Parameters
editIn addition to the standard parameters like pretty
, the Update By Query API
also supports refresh
, wait_for_completion
, wait_for_active_shards
, timeout
and scroll
.
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 Tasks APIs
to cancel or get the status of the task. Elasticsearch will also create a
record of this task as a document at .tasks/task/${taskId}
. This is yours
to keep or remove as you see fit. When you are done with it, delete it so
Elasticsearch can reclaim the space it uses.
wait_for_active_shards
controls how many copies of a shard must be active
before proceeding with the request. See here
for details. timeout
controls how long each write request waits for unavailable
shards to become available. Both work exactly how they work in the
Bulk API. As _update_by_query
uses scroll search, you can also specify
the scroll
parameter to control how long it keeps the "search context" alive,
eg ?scroll=10m
, by default it’s 5 minutes.
requests_per_second
can be set to any positive decimal number (1.4
, 6
,
1000
, etc) and throttles rate at which _update_by_query
issues batches of
index operations by padding each batch with a wait time. The throttling can be
disabled by setting requests_per_second
to -1
.
The throttling is done by waiting between batches so that scroll that
_update_by_query
uses internally can be given a timeout that takes into
account the padding. 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 the requests_per_second
is set to 500
:
target_time = 1000 / 500 per second = 2 seconds wait_time = target_time - delete_time = 2 seconds - .5 seconds = 1.5 seconds
Since the batch is issued as a single _bulk
request 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 -1
.
Response body
editThe JSON response looks like this:
{ "took" : 147, "timed_out": false, "total": 5, "updated": 5, "deleted": 0, "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" : [ ] }
-
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 update by query execution has timed out. -
total
- The number of documents that were successfully processed.
-
updated
- The number of documents that were successfully updated.
-
deleted
- The number of documents that were successfully deleted.
-
batches
- The number of scroll responses pulled back by the update by query.
-
version_conflicts
- The number of version conflicts that the update by query hit.
-
noops
-
The number of documents that were ignored because the script used for
the update by query returned a
noop
value forctx.op
. -
retries
-
The number of retries attempted by update-by-query.
bulk
is the number of bulk actions retried andsearch
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 update 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 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.
Update-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.
Works with the Task API
editYou can fetch the status of all running update-by-query requests with the Task API:
GET _tasks?detailed=true&actions=*byquery
The responses looks like:
{ "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/update/byquery", "status" : { "total" : 6154, "updated" : 3500, "created" : 0, "deleted" : 0, "batches" : 4, "version_conflicts" : 0, "noops" : 0, "retries": { "bulk": 0, "search": 0 }, "throttled_millis": 0 }, "description" : "" } } } } }
this object contains the actual status. It is just like the response json
with the important addition of the |
With the task id you can look up the task directly. The following example
retrieves information about task r1A2WoRbTwKZ516z6NEs5A:36619
:
GET /_tasks/r1A2WoRbTwKZ516z6NEs5A:36619
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 them it’ll come back with a
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.
Works with the Cancel Task API
editAny Update By Query can be canceled using the Task Cancel API:
POST _tasks/r1A2WoRbTwKZ516z6NEs5A:36619/_cancel
The task ID can be found using the tasks API.
Cancellation 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.
Rethrottling
editThe value of requests_per_second
can be changed on a running update by query
using the _rethrottle
API:
POST _update_by_query/r1A2WoRbTwKZ516z6NEs5A:36619/_rethrottle?requests_per_second=-1
The task ID can be found using the tasks API.
Just like when setting it on the _update_by_query
API requests_per_second
can be either -1
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.
Slicing
editUpdate-by-query supports Sliced Scroll to parallelize the updating process. This parallelization can improve efficiency and provide a convenient way to break the request down into smaller parts.
Manual slicing
editSlice an update-by-query manually by providing a slice id and total number of slices to each request:
POST twitter/_update_by_query { "slice": { "id": 0, "max": 2 }, "script": { "source": "ctx._source['extra'] = 'test'" } } POST twitter/_update_by_query { "slice": { "id": 1, "max": 2 }, "script": { "source": "ctx._source['extra'] = 'test'" } }
Which you can verify works with:
GET _refresh POST twitter/_search?size=0&q=extra:test&filter_path=hits.total
Which results in a sensible total
like this one:
{ "hits": { "total": 120 } }
Automatic slicing
editYou can also let update-by-query automatically parallelize using
Sliced Scroll to slice on _uid
. Use slices
to specify the number of
slices to use:
POST twitter/_update_by_query?refresh&slices=5 { "script": { "source": "ctx._source['extra'] = 'test'" } }
Which you also can verify works with:
POST twitter/_search?size=0&q=extra:test&filter_path=hits.total
Which results in a sensible total
like this one:
{ "hits": { "total": 120 } }
Setting slices
to auto
will let Elasticsearch 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 indices, it will choose the number of slices based
on the index with the smallest number of shards.
Adding slices
to _update_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 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
andsize
on a request withslices
are distributed proportionally to each sub-request. Combine that with the point above about distribution being uneven and you should conclude that the usingsize
withslices
might not result in exactlysize
documents being `_update_by_query`ed. - Each sub-requests gets a slightly different snapshot of the source index though these are all taken at approximately the same time.
Picking the number of slices
editIf slicing automatically, setting slices
to auto
will choose a reasonable
number for most indices. If you’re slicing manually or otherwise tuning
automatic slicing, use these guidelines.
Query performance is most efficient when the number of slices
is equal to the
number of shards in the index. If that number is large, (for example,
500) choose a lower number as too many slices
will hurt performance. Setting
slices
higher than the number of shards generally does not improve efficiency
and adds overhead.
Update performance scales linearly across available resources with the number of slices.
Whether query or update performance dominates the runtime depends on the documents being reindexed and cluster resources.
Pick up a new property
editSay 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:
PUT test { "mappings": { "_doc": { "dynamic": false, "properties": { "text": {"type": "text"} } } } } POST test/_doc?refresh { "text": "words words", "flag": "bar" } POST test/_doc?refresh { "text": "words words", "flag": "foo" } PUT test/_mapping/_doc { "properties": { "text": {"type": "text"}, "flag": {"type": "text", "analyzer": "keyword"} } }
This means that new fields won’t be indexed, just stored in |
|
This updates the mapping to add the new |
Searching for the data won’t find anything:
POST test/_search?filter_path=hits.total { "query": { "match": { "flag": "foo" } } }
{ "hits" : { "total" : 0 } }
But you can issue an _update_by_query
request to pick up the new mapping:
POST test/_update_by_query?refresh&conflicts=proceed POST test/_search?filter_path=hits.total { "query": { "match": { "flag": "foo" } } }
{ "hits" : { "total" : 1 } }
You can do the exact same thing when adding a field to a multifield.