[FEATURE] Handle epoch field in string format

[penghuo]

Is your feature request related to a problem? SQL query field if origin date field in string format (epoch value).

A) Create index

PUT sample-index

B) Put index mapping :

PUT /sample-index/_mapping
{
  "properties": {
    "message": {
      "properties":{
        "timestamp_received":{
          "type":"date"
        }
      }
    }
  }
}

Kindly note we have not provided any format (like "strict_date_optional_time" or "epoch_millis") type in above mapping

C) Inserted the doc :

POST sample-index/_doc/1
{
    "message" : {
      "timestamp_received" : "1705642934886"
    }
}

D) Try running SQL query :

POST _plugins/_sql
{
  "query" : "SELECT message.timestamp_received FROM sample-index"
}

{
  "error": {
    "type": "IllegalStateException",
    "reason": "There was internal problem at backend",
    "details": "Construct ExprTimestampValue from \"1705642934886\" failed, unsupported date format."
  },
  "status": 503
}

What solution would you like? Query should works as epoch value in long format.

What alternatives have you considered? n/a

Do you have any additional context? Add any other context or screenshots about the feature request here.

[penghuo]

Related to PR, https://github.com/opensearch-project/sql/pull/1664/

Using strict_date_optional_time||epoch_millis as default format instead of "" https://github.com/opensearch-project/sql/pull/1664/files#diff-81e2e0d0405360026791ecce8e594e933fce50f3dc697217003f1b914dc2cff5R166