_source(Optional, list) Set to false to disable source retrieval (default: true). You can also specify a comma-separated list of the fields you want to retrieve.
batches The number of scroll responses pulled back by the delete by query.
version_conflicts 版本冲突的数目.
noops 对于该API一直是0.
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.