How to skip (don't update) some fields from existing node during import if this field already has a value?

Question

I'm using drupal 7, feeds 7.x-2.0-alpha8. How to skip (don't update) some fields from existing node during import if this field already has a value?

i.e. We periodically import some products with photo (create new and update existing). After that editor can change photo. How can i skip this photo field during next update?

There is some feeds tamper plugin to check is field in updating node is empty? Maybe there is some hook from feeds or feeds tamper?

Answer 1

You can use hook_presave to check if node already has a value and make sure you don't import the new one if that's the case. When using feeds importer nodes have a specific attribute ($node->feeds_item) that you can use to check if it's being updated through feeds.