Passing request_body with GET request? - elasticsearch

Question

Like at this elastic get query I see below example where per my understanding query_string is passed under request body in GET request . Is n't it ? But I believe we can't pass request body with GET request then how come this example is true ?
GET /_search
{
"query": {
"query_string" : {
"default_field" : "content",
"query" : "this AND that OR thus"
}
}
}
In fact when I used the option COPY as CURL from the stated link I see below copied text
curl -X GET "localhost:9200/_search" -H 'Content-Type: application/json' -d'
{
"query": {
"query_string" : {
"default_field" : "content",
"query" : "this AND that OR thus"
}
}
}
'
Am I missing anything here or something wrong in example? In fact I do not see the way to send the request body under Postman tool.

Answer 1

The fact is that you can send a GET request with a body. The current HTTP standard rfc7231 (obsoletes rfc2616 and updates rfc2817) does not strictly define what must happen to a GET request with a body. The previous versions were different in this regard. For that reason, some HTTP servers allow it, but some others don't, I'm afraid. This case is mentioned in the latest standard as follows:
A payload within a GET request message has no defined semantics;
sending a payload body on a GET request might cause some existing
implementations to reject the request.
In terms of Elasticsearch, using using GET for a search request is a design decision. They feel it makes more sense semantically. Because it represents a data retrieving action better than the POST verb.
On the other hand, as mentioned above, a GET request with a body is not supported universally. That's why Postman does not allow you to do so, although Kibana > Dev Tool does it by using cURL. Therefore, the Elasticsearch search API also supports POST requests to search and retrieve information. So, when you cannot make a GET request with a body, you can obtain exactly the same result by making a POST request.

Answer 2

This is actually very interested question. In fact, a lot of HTTP clients aren’t supporting GET requests with body (i just recently face, that iOS client in Cocoa isn’t able to do so).
I also had a lot of discussions with my colleagues - to me after using Elasticsearch for a long time GET with a body sounds like a perfectly fine HTTP request, however some may argue, that GET shouldn’t go with body at all according to HTTP standard. However, I will leave this discussion out of this answer.
In general this leads to a situation, that if you’re using client which not supporting GET, you could either change it to POST or switch to something else - I used to use cURL all the time or Kibana Dev Tools if I needed to construct complex query on the fly