[Doris On ES] [Bug] Error handling for date field with docvalue and inconsistent result for source and docvalue

[wuyunfeng]

1. Before ES 5.x request docvalue fields for date field, the Millisecond timestamp would returned for client, but after 6.4.0 all field which fetched from docvalue would be formatted , this also can be found Elasticsearch issue: Option to allow docvalue_fields of date types to return ms elastic/elasticsearch#27740, the format for date default is just 2020-06-18T12:10:30.000Z.

2. If we index some date field with second timestamp , and query table with enable_docvalue_scan true and false, users would get inconsistent result because the different processing logic for date.

ES documents:

       {
            "_index": "timestamp_test",
            "_type": "doc",
            "_id": "AXLbzdJY516Vuc7SL51m",
            "_score": 1,
            "_source": {
               "k1": "2020-6-25"
            }
         },
         {
            "_index": "timestamp_test",
            "_type": "doc",
            "_id": "AXLbzddn516Vuc7SL51n",
            "_score": 1,
            "_source": {
               "k1": 1592816393000
            }
         }

CREATE EXTERNAL TABLE `timestamp_source` (
  `k1` date NULL COMMENT ""
) ENGINE=ELASTICSEARCH

a. create "enable_docvalue_scan" = "false" table :

For ES 5.5:

mysql> select k1 from timestamp_source;
+------------+
| k1         |
+------------+
| 2020-06-25 | // origin _source value: "2020-6-25"       ----- right
| d444-05-05 | // origin _source value: 1593043200000 (millisecond)   ----- wrong should divided by 1000
+------------+

For ES 6.5 or above:

mysql> select * from timestamp_source;
+------------+
| k1         |
+------------+
| 2020-06-25 | // origin _source value: "2020-6-25"       ----- right
| d444-05-05 | // origin _source value: 1593043200000 (millisecond)   ----- wrong should divided by 1000
+------------+

b. a. create "enable_docvalue_scan" = "true" table :

For ES 5.5:

mysql> select k1 from timestamp_dv; 
+------------+
| k1         |
+------------+
| d451-07-13 |   // 1593043200000   ----- wrong, should divided by 1000
| d444-05-05 | //  1592816393000   ----- wrong, should divided by 1000 
+------------+

For ES 6.5 or above:

mysql> select * from timestamp_dv; 
+------------+
| k1         |
+------------+
| 1970-01-01 | //  value: "2020-06-25T00:00:00.000Z"  ----- wrong GetInt64(value) = 24
| 1970-01-01 | // value: "2020-06-22T08:59:53.000Z"   ----- wrong GetInt64(value) = 24
+------------+