How can curl perform a get request with a data payload?

The introductory materials on ElasticSearch include the following example curl request:

curl -X GET "localhost:9200/_search?pretty" -H 'Content-Type: application/json' -d'
{
    "query": {
        "query_string" : {
            "query" : "(new york city) OR (big apple)",
            "default_field" : "content"
        }
    }
}
'

This request has two parameter which I thought were incompatible:

-X GET, which specifies that the request is a GET.
-d [...], which specifies that the request has a data payload.

I thought that specifying a data payload was only possible in a PUT or POST requests, because GET requests do not have any concept of a data payload. Is this a valid curl command? What does it do, exactly?

Solution

Above curl request is a valid request, in fact, if you have index and data, then you can check the output of your command.

I tried it in my system and ES index and it gave me proper response.

curl -v -X GET "localhost:9500/querytime/_search?pretty" -H 'Content-Type: application/json' -d'
{
    "query": {
        "query_string" : {
            "query" : "(avengers) OR (big apple)",
            "default_field" : "movie_name"
        }
    }
}'
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 9500 (#0)
> GET /querytime/_search?pretty HTTP/1.1
> Host: localhost:9500
> User-Agent: curl/7.64.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 156
>
* upload completely sent off: 156 out of 156 bytes
< HTTP/1.1 200 OK
< content-type: application/json; charset=UTF-8
< content-length: 905
<
{
  "took" : 4,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 3,
      "relation" : "eq"
    },
    "max_score" : 0.14874382,
    "hits" : [
      {
        "_index" : "querytime",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 0.14874382,
        "_source" : {
          "movie_name" : "Avengers: Infinity War"
        }
      }
    ]
  }
}

As mentioned in the official manual of curl command, if you are using *nix based system, then you can search below in the manual of curl.

-G, --get When used, this option will make all data specified with -d, --data, --data-binary or --data-urlencode to be used in an HTTP GET request instead of the POST request that otherwise would be used. The data will be appended to the URL with a '?' separator

As explained in this SO answer, it also depends on the web-server to parse the body in GET request.