重新索引后Elasticsearch不遵循_mapping(Elasticsearch doesn't obey _mapping after reindex)

 我有一个名为last_post_date的字段存储在elasticsearch中。 
 
 它显示为： 
 
...
"last_post_date": "1485281760000",
...
 
 并将映射为： 
 
"last_post_date": {
    "type": "text",
    "fields": {
        "keyword": {
            "type": "keyword",
            "ignore_above": 256
        }
    }
},
 
 现在我创建一个新的索引，映射为： 
 
...
"last_post_date": {
    "type": "date",
    "format": "epoch_millis",
    "index": true,
    "doc_values": true
},
...
 
 并通过以下方式完成重新索引： http ： //127.0.0.1 ：9200 / repindex 
 
 问题是，即使重新索引后，字段的值也会存储为字符串而不是日期，而映射显示： 
 
...
"last_post_date": {
    "type": "date",
    "store": true,
    "format": "epoch_millis"
},
...
 
 知道为什么吗？ 

I have a field called last_post_date stored in elasticsearch.
 
It's shown as:
 
...
"last_post_date": "1485281760000",
...
 
And has the mapping as:
 
"last_post_date": {
    "type": "text",
    "fields": {
        "keyword": {
            "type": "keyword",
            "ignore_above": 256
        }
    }
},
 
Now I create a new index with the mapping as:
 
...
"last_post_date": {
    "type": "date",
    "format": "epoch_millis",
    "index": true,
    "doc_values": true
},
...
 
And do a full reindex via: http://127.0.0.1:9200/_reindex
 
The problem is that even after reindexing the field's value is stored as string instead of date while the mapping shows:
 
...
"last_post_date": {
    "type": "date",
    "store": true,
    "format": "epoch_millis"
},
...
 
Any idea why?

原文：https://stackoverflow.com/questions/42427945