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# UpdateByQueryElasticsearch

This processor executes an update operation against one or more indices using the _update_by_query handler. The query
should be a valid Elasticsearch JSON DSL query (Lucene syntax is not supported). An optional Elasticsearch script can be
specified to execute against the matched documents. An example query with script:

```json
{
  "script": {
    "source": "ctx._source.count++",
    "lang": "painless"
  },
  "query": {
    "match": {
      "username.keyword": "john.smith"
    }
  }
}
```

To update all the contents of an index, this could be used:

```json
{
  "query": {
    "match_all": {}
  }
}
```
