SQL: date and numeric comparison are translated to separate range queries

[elasticmachine]

Original comment by @astefan:

For a query like:

POST /_xpack/sql/translate
{
  "query":"SELECT name.keyword FROM library WHERE name!='NULL' AND release_date >= '2011-06-02' AND release_date <= '2011-06-02' AND match(author,'dan')"
}

or (with numerics):

POST /_xpack/sql/translate
{
  "query":"SELECT name.keyword FROM library WHERE name!='NULL' AND price >= 10 AND price <= 200 AND match(author,'dan')"
}

The translated query uses individual range queries for the lower and upper limits even though the field being used in the query is the same and an optimization like {"range":{"price":{"from":10,"to":200,"include_lower":true,"include_upper":true,"boost":1}}} can be used instead. For the reference, this is the translated query at the moment (irrelevant parts not provided):

...
  "query": {
    "bool": {
      "filter": [
        {
          "bool": {
            "filter": [
              {
                "bool": {
                  "filter": [
                    {
                      "bool": {
                        "must_not": [
                          {
                            "term": {
                              "name.keyword": {
                                "value": "NULL",
                                "boost": 1
                              }
                            }
                          }
                        ],
                        "adjust_pure_negative": true,
                        "boost": 1
                      }
                    },
                    {
                      "range": {
                        "price": {
                          "from": 10,
                          "to": null,
                          "include_lower": true,
                          "include_upper": false,
                          "boost": 1
                        }
                      }
                    }
                  ],
                  "adjust_pure_negative": true,
                  "boost": 1
                }
              },
              {
                "range": {
                  "price": {
                    "from": null,
                    "to": 200,
                    "include_lower": false,
                    "include_upper": true,
                    "boost": 1
                  }
                }
              }
            ],
            "adjust_pure_negative": true,
            "boost": 1
          }
        },
...