[[search-multi-search]]
== Multi Search API

The multi search API allows to execute several search requests within
the same API. The endpoint for it is `_msearch`.

The format of the request is similar to the bulk API format, and the
structure is as follows (the structure is specifically optimized to
reduce parsing if a specific search ends up redirected to another node):

[source,js]
--------------------------------------------------
header\n
body\n
header\n
body\n
--------------------------------------------------

The header part includes which index / indices to search on, optional
(mapping) types to search on, the `search_type`, `preference`, and
`routing`. The body includes the typical search body request (including
the `query`, `aggregations`, `from`, `size`, and so on). Here is an example:

[source,js]
--------------------------------------------------
$ cat requests
{"index" : "test"}
{"query" : {"match_all" : {}}, "from" : 0, "size" : 10}
{"index" : "test", "search_type" : "dfs_query_then_fetch"}
{"query" : {"match_all" : {}}}
{}
{"query" : {"match_all" : {}}}

{"query" : {"match_all" : {}}}
{"search_type" : "dfs_query_then_fetch"}
{"query" : {"match_all" : {}}}

$ curl -XGET localhost:9200/_msearch --data-binary "@requests"; echo
--------------------------------------------------

Note, the above includes an example of an empty header (can also be just
without any content) which is supported as well.

The response returns a `responses` array, which includes the search
response for each search request matching its order in the original
multi search request. If there was a complete failure for that specific
search request, an object with `error` message will be returned in place
of the actual search response.

The endpoint allows to also search against an index/indices and
type/types in the URI itself, in which case it will be used as the
default unless explicitly defined otherwise in the header. For example:

[source,js]
--------------------------------------------------
$ cat requests
{}
{"query" : {"match_all" : {}}, "from" : 0, "size" : 10}
{}
{"query" : {"match_all" : {}}}
{"index" : "test2"}
{"query" : {"match_all" : {}}}

$ curl -XGET localhost:9200/test/_msearch --data-binary @requests; echo
--------------------------------------------------

The above will execute the search against the `test` index for all the
requests that don't define an index, and the last one will be executed
against the `test2` index.

The `search_type` can be set in a similar manner to globally apply to
all search requests.

The msearch's `max_concurrent_searches` request parameter can be used to control
the maximum number of concurrent searches the multi search api will execute.
This default is based on the number of data nodes and the default search thread pool size.

[float]
[[msearch-security]]
=== Security

See <<url-access-control>>
