> For the complete documentation index, see [llms.txt](https://hezhiqiang.gitbook.io/elasticsearch/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hezhiqiang.gitbook.io/elasticsearch/distributed_crud/bulk_requests.md).

# 批量请求

The patterns for the `mget` and `bulk` APIs are similar to those for individual documents. The difference is that the requesting node knows in which shard each document lives. It breaks up the multi-document request into a multi-document request *per shard*, and forwards these in parallel to each participating node.

Once it receives answers from each node, it collates their responses into a single response, which it returns to the client.

\[\[img-distrib-mget]] .Retrieving multiple documents with `mget` image::images/04-05\_mget.png\["Retrieving multiple documents with mget"]

Below we list the sequence of steps necessary to retrieve multiple documents with a single `mget` request, as depicted in <>:

1. The client sends an `mget` request to `Node_1`.
2. `Node 1` builds a multi-get request per shard, and forwards these requests in parallel to the nodes hosting each required primary or replica shard. Once all replies have been received, `Node 1` builds the response and returns it to the client.

A `routing` parameter can be set for each document in the `docs` array, and the `preference` parameter can be set for the top-level `mget` request.

\[\[img-distrib-bulk]] .Multiple document changes with `bulk` image::images/04-06\_bulk.png\["Multiple document changes with bulk"]

Below we list the sequence of steps necessary to execute multiple `create`, `index`, `delete` and `update` requests within a single `bulk` request, as depicted in <>:

1. The client sends a `bulk` request to `Node_1`.
2. `Node 1` builds a bulk request per shard, and forwards these requests in parallel to the nodes hosting each involved primary shard.
3. The primary shard executes each action serially, one after another. As each action succeeds, the primary forwards the new document (or deletion) to its replica shards in parallel, then moves on to the next action. Once all replica shards report success for all actions, the node reports success to the requesting node, which collates the responses and returns them to the client.

The `bulk` API also accepts the `replication` and `consistency` parameters at the top-level for the whole `bulk` request, and the `routing` parameter in the metadata for each request.