Changing the query fields from settings.php without including the rendered item field will show no results because Solr fields names are being generated in wrong way and without considering the boost that has been set in the search api index fields.
1- Enable and configure Search Api Solr and Search API Federated Solr.
2- in setting.php add other full text fields than rendered item like :
$config['search_api_federated_solr.search_app.settings']['index']['query_fields'] = [
// targeted full text fields machine names as they are in Search api index fields
'body'
];
3- Go to search page that has been created from Search API Federated Solr and enter a keyword that you are sure its in the body of a node then submit and you will have no results.
Needs review
4.0
Code
This patch allows to search in all full text fields that has been added to the Search api index fields in case there are no fields has been added to the settings.php and it also fixes the score calculating as now the boost values that has been set in Search api index fields will be considered.