Feeds XPath Parser - Update existing content I have created a Feed Importer and used XPath Parser for mapping. I have problem with updating a existing content. For example I have this xml structure.

&lt;node&gt;
  &lt;nid&gt;1&lt;/nid&gt;
  &lt;title&gt;Title 1&lt;/title&gt;
&lt;/node&gt;
&lt;node&gt;
  &lt;nid&gt;2&lt;/nid&gt;
  &lt;title&gt;Title 2&lt;/title&gt;
&lt;/node&gt;


I started importer and everything is OK. I set NID as unique and check "Update existing content" in Node Process settings. So when I run importer again whit the same data this nodes have updated again.

Why have been updated ? The source is the same and don't any difference. Should It display, there is no new content to add if I start importer again and again with the same data ?

Thank you!
it doesn't recognized the nid field as unique, 

What is  the field associated with the nid value? 

If you have a custom field associated with the nid :

You should install https://www.drupal.org/project/field_validation

and add the validation of the field at 
http://yourwebsite/admin/structure/field_validation

and set the validator with the value "Unique values".

Sometimes a space in the value of the feed can cause this in this case you can use tamper for trim spaces :
https://www.drupal.org/project/feeds_tamper