# Does update\_by\_query always reindex entire document **URL:** \ **Category:** Elasticsearch\ **Created:** [January 30, 2019, 1:35pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363 "2019-01-30T13:35:39Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 30, 2019, 1:35pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/1 "2019-01-30T13:35:39Z")
I'm trying to figure out if the `_update_by_query` elasticsearch endpoint reindexes entire documents. I ran a batch process that generated and ran thousands of update\_by\_query statements. My CPU escalated after some time so I stopped running them. That was about a week ago, and my CPU is still abnormally high. When I check the nodes in my cluster, one of them has unusually high processing percentage. I checked the hot threads against that node and it appears to still be processing update tasks. I stopped running the updates over a week ago. How could this node still be processing updates? My thinking was that it's reindexing documents that were affected by the updates. Please share any thoughts. ---
**Author:** ![nik9000](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/nik9000/32/44947_2.png) [@nik9000](https://discuss.elastic.co/u/nik9000)\ **Post date:** [January 30, 2019, 1:59pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/2 "2019-01-30T13:59:24Z")
The tasks API should tell you if you are still running the `_update_by_query`. IIRC one of the funny things about `_update_by_query` is that it'll perform a noop update of all documents if you give it an empty body. This might be what is going on here. ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 30, 2019, 2:06pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/3 "2019-01-30T14:06:13Z")
So the tasks that are running against the heavy processing node look like this.. I don't think these are `_update_by_query` tasks, but the hot threads appeared otherwise. ``` "C_i25yS5SWSdrv3NPEoHEA": { "name": "C_i25yS", "roles": [ "data", "ingest" ], "tasks": { "C_i25yS5SWSdrv3NPEoHEA:186466469": { "node": "C_i25yS5SWSdrv3NPEoHEA", "id": 186466469, "type": "transport", "action": "cluster:monitor/tasks/lists", "start_time_in_millis": 1548856970331, "running_time_in_nanos": 2978262, "cancellable": false, "headers": {} }, "C_i25yS5SWSdrv3NPEoHEA:186466471": { "node": "C_i25yS5SWSdrv3NPEoHEA", "id": 186466471, "type": "direct", "action": "cluster:monitor/tasks/lists[n]", "start_time_in_millis": 1548856970333, "running_time_in_nanos": 101917, "cancellable": false, "parent_task_id": "C_i25yS5SWSdrv3NPEoHEA:186466469", "headers": {} }, "C_i25yS5SWSdrv3NPEoHEA:186466470": { "node": "C_i25yS5SWSdrv3NPEoHEA", "id": 186466470, "type": "netty", "action": "internal:discovery/zen/publish/commit", "start_time_in_millis": 1548856970332, "running_time_in_nanos": 1706067, "cancellable": false, "headers": {} } } } ``` ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 30, 2019, 2:10pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/4 "2019-01-30T14:10:17Z")
The action on the task would be something like `indices:data/write/update/byquery` if it was an update by query still running. ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 31, 2019, 2:51pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/5 "2019-01-31T14:51:09Z")
@nik9000 Any other thoughts here as to why CPU would still be so high? ---
**Author:** ![nik9000](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/nik9000/32/44947_2.png) [@nik9000](https://discuss.elastic.co/u/nik9000)\ **Post date:** [January 31, 2019, 7:18pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/6 "2019-01-31T19:18:29Z")
Right, update by query isn't running. I'd check the `hot_threads` API. If the CPU is super high on any one task it'll jump right out. ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 31, 2019, 8:41pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/7 "2019-01-31T20:41:23Z")
@nik9000 The `hot_threads` aren't particularly helpful to me, not really sure what to take away from it. Here's what it's reading for the heavy CPU node. Nothing really stands out to me. The response also constantly changes. `"::: {C_i25yS}{C_i25yS5SWSdrv3NPEoHEA}{IlzCv7ROQSaMm6IGV_Z88A}{x.x.x.x}{x.x.x.x:9300}{zone=us-west-2b}\n Hot threads at 2019-01-31T20:38:49.441Z, interval=500ms, busiestThreads=3, ignoreIdleThreads=true:\n \n 68.3% (341.5ms out of 500ms) cpu usage by thread 'elasticsearch[C_i25yS][clusterApplierService#updateTask][T#1]'\n 2/10 snapshots sharing following 13 elements\n org.elasticsearch.indices.store.IndicesStore$ShardActiveResponseHandler.lambda$allNodesResponded$2(IndicesStore.java:289)\n org.elasticsearch.indices.store.IndicesStore$ShardActiveResponseHandler$$Lambda$1704/1699952741.accept(Unknown Source)\n org.elasticsearch.cluster.service.ClusterApplierService.lambda$runOnApplierThread$0(ClusterApplierService.java:307)\n org.elasticsearch.cluster.service.ClusterApplierService$$Lambda$1706/1089848983.apply(Unknown Source)\n org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.apply(ClusterApplierService.java:156)\n org.elasticsearch.cluster.service.ClusterApplierService.runTask(ClusterApplierService.java:400)\n org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.run(ClusterApplierService.java:161)\n org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:573)\n org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:244)\n org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:207)\n java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n java.lang.Thread.run(Thread.java:748)\n 8/10 snapshots sharing following 2 elements\n java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n java.lang.Thread.run(Thread.java:748)\n\n"` ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [January 31, 2019, 8:46pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/8 "2019-01-31T20:46:04Z")
For some reason the `human` and `pretty` URL params do not format the response at all. ---
**Author:** ![ahummel25](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@ahummel25](https://discuss.elastic.co/u/ahummel25)\ **Post date:** [February 7, 2019, 2:46pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/9 "2019-02-07T14:46:58Z")
@nik9000 Do you see anything in the hot threads above that may be useful? Or anything else that may help resolve my issue? ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [March 7, 2019, 2:47pm UTC](https://discuss.elastic.co/t/does-update-by-query-always-reindex-entire-document/166363/10 "2019-03-07T14:47:01Z")
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