Drupal Apache solr does not return "no results founds" I'm using Apache Solr 7.x-1.1 with Drupal. It was working fine but something happened and when I search for dummy data that I'm sure that is not found in my site, the search result will be all nodes in my site instead of returning "your search yielded no results". It was working perfect before but I don't know what I did so this occurred.
I met the same issue, and the main reason was the solr 'bias' settings in admin/config/search/apachesolr/settings/solr_search/bias 

I changed some of its configuration. the solution is clicking 'reset to default' button.