OpenSearch/docs/reference/search/multi-search.asciidoc

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

Executes several searches with a single API request.

[source,console]
--------------------------------------------------
GET twitter/_msearch
{ }
{"query" : {"match" : { "message": "this is a test"}}}
{"index": "twitter2"}
{"query" : {"match_all" : {}}}
--------------------------------------------------
// TEST[setup:twitter]

[[search-multi-search-api-request]]
==== {api-request-title}

`GET /<index>/_msearch`


[[search-multi-search-api-desc]]
==== {api-description-title}

The multi search API executes several searches from a single API request.
The format of the request is similar to the bulk API format and makes use 
of the newline delimited JSON (NDJSON) format.

The structure is as follows:

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

This structure is specifically optimized to reduce parsing if a specific search
ends up redirected to another node.

[IMPORTANT]
====
The final line of data must end with a newline character `\n`. Each newline
character may be preceded by a carriage return `\r`. When sending requests to
this endpoint the `Content-Type` header should be set to `application/x-ndjson`.
====

[[search-multi-search-api-path-params]]
==== {api-path-parms-title}

include::{docdir}/rest-api/common-parms.asciidoc[tag=index]
+
To search all indices, use `_all` or omit this parameter.

[[search-multi-search-api-query-params]]
==== {api-query-parms-title}

include::{docdir}/rest-api/common-parms.asciidoc[tag=allow-no-indices]

`ccs_minimize_roundtrips`::
(Optional, boolean)
If `true`, network roundtrips between the coordinating node and remote clusters
are minimized for {ccs} requests. Defaults to `true`. See
<<ccs-network-delays>>.

include::{docdir}/rest-api/common-parms.asciidoc[tag=expand-wildcards]
+
Defaults to `open`.

`ignore_throttled`::
(Optional, boolean)
If `true`, concrete, expanded or aliased indices are ignored when throttled.
Defaults to `false`.

include::{docdir}/rest-api/common-parms.asciidoc[tag=index-ignore-unavailable]

`max_concurrent_searches`::
(Optional, integer)
Maximum number of concurrent searches the multi search API can execute.

`max_concurrent_shard_requests`::
+
--
(Optional, integer)
Maximum number of concurrent shard requests that each sub-search request
executes per node.  Defaults to `5`. 

You can use this parameter to prevent a request from overloading a cluster. For
example, a default request hits all indices in a cluster. This could cause shard
request rejections if the number of shards per node is high.

In certain scenarios, parallelism isn't achieved through concurrent requests. In
those cases, a low value in this  parameter could result in poor performance.
For example, in an environment where a very low number of concurrent search
requests are expected, a higher value in this parameter may improve performance.
--

`pre_filter_shard_size`::
(Optional, integer)
Defines a threshold that enforces a pre-filter roundtrip to prefilter search
shards based on query rewriting if the number of shards the search request
expands to exceeds the threshold. This filter roundtrip can limit the number of
shards significantly if for instance a shard can not match any documents based
on it's rewrite method i.e., if date filters are mandatory to match but the
shard bounds and the query are disjoint. Defaults to `128`.

`rest_total_hits_as_int`::
(Optional, boolean)
If `true`, `hits.total` are returned as an integer in the
response. Defaults to `false`, which returns an object.

`routing`::
(Optional, string)
Custom <<mapping-routing-field,routing value>> used to route search operations
to a specific shard.

`search_type`::
+
--
(Optional, string)
Indicates whether global term and document frequencies should be used when
scoring returned documents. 

Options are:

`query_then_fetch`::
(default)
Documents are scored using local term and document frequencies for the shard.
This is usually faster but less accurate.

`dfs_query_then_fetch`::
Documents are scored using global term and document frequencies across all
shards. This is usually slower but more accurate.
--
  
`typed_keys`::
(Optional, boolean)
Specifies whether aggregation and suggester names should be prefixed by their
respective types in the response.

[[search-multi-search-api-request-body]]
==== {api-request-body-title}

The request body contains a newline-delimited list of search `<header>` and
search `<body>` objects.

`<header>`::
+
--
(Required, object)
Contains parameters used to limit or change the subsequent search body request.

This object is required for each search body but can be empty (`{}`) or a blank
line.
--

`allow_no_indices`:::
(Optional, boolean)
If `true`, the request does *not* return an error if a wildcard expression or
`_all` value retrieves only missing or closed indices.
+
This parameter also applies to <<indices-aliases,index aliases>> that point to a
missing or closed index.

include::{docdir}/rest-api/common-parms.asciidoc[tag=expand-wildcards]
+
Defaults to `open`.

`ignore_unavailable`:::
(Optional, boolean) If `true`, documents from missing or closed indices are not
included in the response. Defaults to `false`.

`index`:::
(Optional, string or array of strings)
Index name or <<indices-aliases,alias>> used to limit the request. Wildcard
expressions are supported. You can specify multiple indices as an array.

`preference`:::
(Optional, string)
Node or shard used to perform the search. Random by default.

`request_cache`:::
(Optional, boolean)
If `true`, the request cache can be used for this search. Defaults to
index-level settings. See <<shard-request-cache>>.

`routing`:::
(Optional, string)
Custom <<mapping-routing-field,routing value>> used to route search operations
to a specific shard.

`search_type`:::
+
--
(Optional, string)
Indicates whether global term and document frequencies should be used when
scoring returned documents. 

Options are:

`query_then_fetch`::
(default)
Documents are scored using local term and document frequencies for the shard.
This is usually faster but less accurate.

`dfs_query_then_fetch`::
Documents are scored using global term and document frequencies across all
shards. This is usually slower but more accurate.
--

`<body>`::
(Optional, object)
Contains parameters for a search request:

`aggregations`:::
(Optional, <<_structuring_aggregations,aggregation object>>)
Aggregations you wish to run during the search. See <<search-aggregations>>.

`query`:::
(Optional, <<query-dsl,query DSL object>>) Query you wish to run during the
search. Hits matching this query are returned in the response.

`from`:::
(Optional, integer)
Starting offset for returned hits. Defaults to `0`.

`size`:::
(Optional, integer)
Number of hits to return. Defaults to `10`.

[[search-multi-search-api-response-body]]
==== {api-response-body-title}

`responses`::
  (array) Includes the search response and status code for each search request 
  matching its order in the original multi search request. If there was a  
  complete failure for a specific search request, an object with `error` message 
  and corresponding status code will be returned in place of the actual search 
  response.


[[search-multi-search-api-example]]
==== {api-examples-title}

The header part includes which index / indices 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).

[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" : {}}}
--------------------------------------------------
// NOTCONSOLE

[source,js]
--------------------------------------------------
$ curl -H "Content-Type: application/x-ndjson" -XGET localhost:9200/_msearch --data-binary "@requests"; echo
--------------------------------------------------
// NOTCONSOLE

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


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

[source,console]
--------------------------------------------------
GET twitter/_msearch
{}
{"query" : {"match_all" : {}}, "from" : 0, "size" : 10}
{}
{"query" : {"match_all" : {}}}
{"index" : "twitter2"}
{"query" : {"match_all" : {}}}
--------------------------------------------------
// TEST[setup:twitter]

The above will execute the search against the `twitter` index for all the
requests that don't define an index, and the last one will be executed
against the `twitter2` index.

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


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

See <<url-access-control>>


[[template-msearch]]
==== Template support

Much like described in <<search-template>> for the _search resource, _msearch
also provides support for templates. Submit them like follows for inline 
templates:

[source,console]
-----------------------------------------------
GET _msearch/template
{"index" : "twitter"}
{ "source" : "{ \"query\": { \"match\": { \"message\" : \"{{keywords}}\" } } } }", "params": { "query_type": "match", "keywords": "some message" } }
{"index" : "twitter"}
{ "source" : "{ \"query\": { \"match_{{template}}\": {} } }", "params": { "template": "all" } }
-----------------------------------------------
// TEST[setup:twitter]


You can also create search templates:

[source,console]
------------------------------------------
POST /_scripts/my_template_1
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "match": {
                    "message": "{{query_string}}"
                }
            }
        }
    }
}
------------------------------------------
// TEST[setup:twitter]


[source,console]
------------------------------------------
POST /_scripts/my_template_2
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "term": {
                    "{{field}}": "{{value}}"
                }
            }
        }
    }
}
------------------------------------------
// TEST[continued]

You can use search templates in a _msearch:

[source,console]
-----------------------------------------------
GET _msearch/template
{"index" : "main"}
{ "id": "my_template_1", "params": { "query_string": "some message" } }
{"index" : "main"}
{ "id": "my_template_2", "params": { "field": "user", "value": "test" } }
-----------------------------------------------
// TEST[continued]


[[multi-search-partial-responses]]
==== Partial responses

To ensure fast responses, the multi search API will respond with partial results 
if one or more shards fail. See <<shard-failures, Shard failures>> for more 
information.