Before indexing, you can add this field in your manage_schema and refresh collection. Then do indexing by sending required page or properties to your collection. Custom Manipulation logic you need to write at index service.
Not sure, but it would it be totally server side manipulation where you may not have much control. I would recommend amending the values before triggering the SOLR call.
Before indexing, you can add this field in your manage_schema and refresh collection. Then do indexing by sending required page or properties to your collection. Custom Manipulation logic you need to write at index service.