OpenSearch/docs/reference/search/count.asciidoc

[[search-count]]
== Count API

The count API allows to easily execute a query and get the number of
matches for that query. It can be executed across one or more indices
and across one or more types. The query can either be provided using a
simple query string as a parameter, or using the
<<query-dsl,Query DSL>> defined within the request
body. Here is an example:

[source,js]
--------------------------------------------------
$ curl -XGET 'http://localhost:9200/twitter/tweet/_count?q=user:kimchy'

$ curl -XGET 'http://localhost:9200/twitter/tweet/_count' -d '
{
    "query" : {
        "term" : { "user" : "kimchy" }
    }
}'
--------------------------------------------------

NOTE: The query being sent in the body must be nested in a `query` key, same as
the <<search-search,search api>> works

Both examples above do the same thing, which is count the number of
tweets from the twitter index for a certain user. The result is:

[source,js]
--------------------------------------------------
{
    "count" : 1,
    "_shards" : {
        "total" : 5,
        "successful" : 5,
        "failed" : 0
    }
}
--------------------------------------------------

The query is optional, and when not provided, it will use `match_all` to
count all the docs.

[float]
=== Multi index, Multi type

The count API can be applied to <<search-multi-index-type,multiple types in multiple indices>>.

[float]
=== Request Parameters

When executing count using the query parameter `q`, the query passed is
a query string using Lucene query parser. There are additional
parameters that can be passed:

[cols="<,<",options="header",]
|=======================================================================
|Name |Description
|df |The default field to use when no field prefix is defined within the
query.

|analyzer |The analyzer name to be used when analyzing the query string.

|default_operator |The default operator to be used, can be `AND` or
`OR`. Defaults to `OR`.

|terminate_after |The maximum count for each shard, upon
reaching which the query execution will terminate early.
If set, the response will have a boolean field `terminated_early` to
indicate whether the query execution has actually terminated_early.
Defaults to no terminate_after.
|=======================================================================

[float]
=== Request Body

The count can use the <<query-dsl,Query DSL>> within
its body in order to express the query that should be executed. The body
content can also be passed as a REST parameter named `source`.

Both HTTP GET and HTTP POST can be used to execute count with body.
Since not all clients support GET with body, POST is allowed as well.

[float]
=== Distributed

The count operation is broadcast across all shards. For each shard id
group, a replica is chosen and executed against it. This means that
replicas increase the scalability of count.

[float]
=== Routing

The routing value (a comma separated list of the routing values) can be
specified to control which shards the count request will be executed on.