How can I set default field value when updating ES mapping
<p>I have "stores" index in elasticsearch and want to add "chain" field with following json:</p>

<pre><code>{
"properties": {
    "chain": {
        "type": "string",
        "store": true
    }
}
</code></pre>

<p>How can I set default value for all existiong documents in the index?</p>