query by timestamp range not working unless with keyword

Question

Newbie question on ElasticSearch:

I have following data with http://localhost:9200/tutorial/_doc/7:

"_index":"tutorial","_type":"_doc","_id":"7","_version":3,"_seq_no":25,"_primary_term":2,"found":true,
"_source":{
  "message": "error",
  "@timestamp": "2022-05-16T09:40:00"
}

and I'm trying to find all records with @timestamp between 2022-05-16T09:30:00 and 2022-05-16T09:50:00 with following request:

POST http://localhost:9200/tutorial/_search
Content-Type: application/json

{
  "query": {
    "bool": {
      "filter": {
        "bool": {
          "must": [
            {
              "range": {
                "@timestamp.keyword": {
                  "gt": "2022-05-16T09:30:00",
                  "lte": "2022-05-16T09:50:00"
                }
              }
            }
          ]
        }
      }
    }
  }
}

The question I have, is that why do I have to use @timestamp.keyword but not just @timestamp for the value under range? If I use the one without keyword, I'll get nothing back.

A bit context, I'm setting up Elastalert which requires a @timestamp field. I checked that the requests it sends to ElasticSearch put @timestamp as the range without keyword, therefore it's not giving me any value.

Result for http://localhost:9200/tutorial if it helps:

{
   "tutorial":{
      "aliases":{
         
      },
      "mappings":{
         "properties":{
            "@timestamp":{
               "type":"text",
               "fields":{
                  "keyword":{
                     "type":"keyword",
                     "ignore_above":256
                  }
               },
               "fielddata":true
            },
            "message":{
               "type":"text",
               "fields":{
                  "keyword":{
                     "type":"keyword",
                     "ignore_above":256
                  }
               }
            }
         }
      },
      "settings":{
         "index":{
            "routing":{
               "allocation":{
                  "include":{
                     "_tier_preference":"data_content"
                  }
               }
            },
            "number_of_shards":"1",
            "provided_name":"tutorial",
            "creation_date":"1652405360958",
            "number_of_replicas":"1",
            "uuid":"OuynpaOiRyqQ1sj-b2xuYw",
            "version":{
               "created":"7170399"
            }
         }
      }
   }
}

Answer 1

Your @timestamp field is not mapped correctly, as text/keyword field types are not appropriate for date values. You need to change your mapping to this instead:

        "@timestamp":{
           "type":"date"
        },

Then you'll be able to run your range query on @timestamp