Update records in ElasticSearch

Hello,

I had like to update the logdate column for all records in a specific index. From what I have read so far, it seems that it is not possible? I am correct?

Here's a sample of a document:

{
            "_index": "logstash-01-2015",
            "_type": "ufdb",
            "_id": "AU__EvrALg15uxY1Wxf9",
            "_score": 1,
            "_source": {
               "message": "2015-08-14 06:50:05 [31946] PASS  level2      10.249.10.70    level2     ads       http://ad.360yield.com/unpixel.... GET",
               "@version": "1",
               "@timestamp": "2015-09-24T11:17:57.389Z",
               "type": "ufdb",
               "file": "/usr/local/ufdbguard/logs/ufdbguardd.log",
               "host": "PROXY-DEV",
               "offset": "3983281700",
               "logdate": "2015-08-14T04:50:05.000Z",
               "status": "PASS",
               "group": "level2",
               "clientip": "10.249.10.70",
               "category": "ads",
               "url": "http://ad.360yield.com/unpixel....",
               "method": "GET",
               "tags": [
                  "_grokparsefailure"
               ]
            }
         }

Where are you reading that?

https://www.elastic.co/guide/en/elasticsearch/guide/current/update-doc.html
https://www.elastic.co/guide/en/elasticsearch/guide/current/partial-updates.html