ElasticSearch增加字段并对历史数据赋初始值

elasticsearch如何为指定索引中类型添加字段并赋初值，就像数据库中添加字段为老的数据赋初始值一样。

用update_by_query结合script可以办到，例如:

POST my_index/_update_by_query
{
  "script": {
    "lang": "painless",
    "inline": "if (ctx._source.like== null) {ctx._source.like= 'i like it'}"
  }
}

    @Test
    public void testInitUpdateByQuery() {

        String like = "i like it";

        UpdateByQueryRequest updateByQueryRequest = new UpdateByQueryRequest(INDEX_NAME);
        updateByQueryRequest.setDocTypes("_doc");
        /// updateByQueryRequest.setQuery(QueryBuilders.termQuery("gameId", 55555));

        // 修改操作
        // script 为更新内容 切记若为字符类型需要加单引号 "'" 拼接
        updateByQueryRequest.setScript(new Script( "if (ctx._source.like == null) {ctx._source.like= '" + like + "'}"));
        /// indexRequest.script(new Script("ctx._source.like = \"i like it\""))

        try {
            BulkByScrollResponse response = client.updateByQuery(updateByQueryRequest, RequestOptions.DEFAULT);

            logger.info("testInitUpdateByQuery response:{}", JSON.toJSONString(response));
            System.out.println("testInitUpdateByQuery response=" + JSON.toJSONString(response));
        } catch (Exception e) {
            logger.error("testInitUpdateByQuery e:{}", e);

        }
    }

ElasticSearch 已存在mapping文档新增字段（ 参考链接 https://blog.csdn.net/MrLiar17/article/details/108245497）