receive _type not indexed error, but documentation says _type is always indexed

[tonyyanga]

Elasticsearch version (bin/elasticsearch --version):

Version: 6.3.0, Build: default/zip/424e937/2018-06-11T23:38:03.357887Z, JVM: 1.8.0_171

Plugins installed: None

JVM version (java -version):

openjdk version "1.8.0_171"
OpenJDK Runtime Environment (build 1.8.0_171-8u171-b11-1~bpo8+1-b11)
OpenJDK 64-Bit Server VM (build 25.171-b11, mixed mode)

OS version (uname -a if on a Unix-like system):

Linux tony-laptop 3.16.0-4-amd64 #1 SMP Debian 3.16.51-3 (2017-12-13) x86_64 GNU/Linux

Description of the problem including expected versus actual behavior:

I run a query on _type field and received HTTP 400 for "cannot search on field [_type] since it is not indexed".

According to the documentation, "The _type field is indexed in order to make searching by type name fast." I expect to receive a correct result not an error.

Steps to reproduce:

Create mappings:

PUT /test_schema_1

{
  "settings":{
    "index":{
      "number_of_shards":1,
      "number_of_replicas":0
    }
  }
}

PUT /test_schema_1/_mapping/test_table_1

{"test_table_1":{"properties":{"text_field":{"type":"text"}}}}

Query:

POST /test_schema_1/test_table_1/_search?size=4000&preference=_shards%3A0&scroll=300000ms

{
  "from" : 0,
  "size" : 4000,
  "query" : {
    "range" : {
      "_type" : {
        "from" : " ",
        "to" : null,
        "include_lower" : false,
        "include_upper" : true,
        "boost" : 1.0
      }
    }
  }
}

Response:

{
    "error": {
        "root_cause": [
            {
                "type": "query_shard_exception",
                "reason": "failed to create query: {\n  \"range\" : {\n    \"_type\" : {\n      \"from\" : \" \",\n      \"to\" : null,\n      \"include_lower\" : false,\n      \"include_upper\" : true,\n      \"boost\" : 1.0\n    }\n  }\n}",
                "index_uuid": "B6LluE64RhqZhIoVufFXSQ",
                "index": "test_schema_1"
            }
        ],
        "type": "search_phase_execution_exception",
        "reason": "all shards failed",
        "phase": "query",
        "grouped": true,
        "failed_shards": [
            {
                "shard": 0,
                "index": "test_schema_1",
                "node": "7RkRZhIBQPKc43Lyr6ZY4A",
                "reason": {
                    "type": "query_shard_exception",
                    "reason": "failed to create query: {\n  \"range\" : {\n    \"_type\" : {\n      \"from\" : \" \",\n      \"to\" : null,\n      \"include_lower\" : false,\n      \"include_upper\" : true,\n      \"boost\" : 1.0\n    }\n  }\n}",
                    "index_uuid": "B6LluE64RhqZhIoVufFXSQ",
                    "index": "test_schema_1",
                    "caused_by": {
                        "type": "illegal_argument_exception",
                        "reason": "Cannot search on field [_type] since it is not indexed."
                    }
                }
            }
        ]
    },
    "status": 400
}

I am aware that _type is being deprecated. Should the documentation be updated to reflect that _type is no longer indexed? Or is there a bug?

[elasticmachine]

Pinging @elastic/es-search-aggs

[cbuescher]

I think the documentation might be off. Consider this PR that mentions that for single-type indices (which new ones on 6.x are by default) "_type" is no longer indexed).

Note that e.g. match ,term or simple_query_string queries work as long as you don't use e.g. wildcards:

POST /test_schema_1/test_table_1/_search
{
  "query" : {
    "match": {
      "_type": "test_table_1"
    }
  }
}

POST /test_schema_1/test_table_1/_search
{
  "query" : {
    "term": {
      "_type": {
        "value": "test_table_1"
      }
    }
  }
}

POST /test_schema_1/test_table_1/_search
{
  "query" : {
    "simple_query_string": {
      "query": "test_table_1",
      "fields": ["_type"]
    }
  }
}