Explain API does not support POST

[polyfractal]

It looks like the Explain API does not support POST requests, which means that certain clients will be unable to utilize it since they don't support GET with request bodies (notably javascript clients).

Any chance of adding POST support to Explain like we have for the other GET methods?

Demonstration, on 0.20.5:

$ curl -XGET localhost:9200/test/benchmark/Yju6VrbaTUauZVMXhU5IBw/_explain?pretty -d '{
  "query":{
    "match":{
      "field1":"pattern"
    }
  }
}'

{
  "ok" : true,
  "_index" : "test",
  "_type" : "benchmark",
  "_id" : "Yju6VrbaTUauZVMXhU5IBw",
  "matched" : true,
  "explanation" : {
    "value" : 0.33165708,
    "description" : "weight(field1:pattern in 26), product of:",
    "details" : [ {
      "value" : 0.99999994,
      "description" : "queryWeight(field1:pattern), product of:",
      "details" : [ {
        "value" : 3.5376759,
        "description" : "idf(docFreq=263631, maxDocs=3335007)"
      }, {
        "value" : 0.28267145,
        "description" : "queryNorm"
      } ]
    }, {
      "value" : 0.3316571,
      "description" : "fieldWeight(field1:pattern in 26), product of:",
      "details" : [ {
        "value" : 1.0,
        "description" : "tf(termFreq(field1:pattern)=1)"
      }, {
        "value" : 3.5376759,
        "description" : "idf(docFreq=263631, maxDocs=3335007)"
      }, {
        "value" : 0.09375,
        "description" : "fieldNorm(field=field1, doc=26)"
      } ]
    } ]
  }



$ curl -XPOST localhost:9200/test/benchmark/Yju6VrbaTUauZVMXhU5IBw/_explain?pretty -d '{
  "query":{
    "match":{
      "field1":"pattern"
    }
  }
}'

No handler found for uri [/test/benchmark/Yju6VrbaTUauZVMXhU5IBw/_explain?pretty] and method [POST]

[martijnvg]

Yes, it makes sense to add this.

[polyfractal]

Great, thanks!