I am using Search API solr on my site. To get better search results I would like to boost the relevance by the value of a certain numeric field. Say, all items have a field A, which is numeric. Now I want to boost the relevance of those itemes by the value of field a, so that, if As value is higher the relevance of the item becomes higher too. I have absolutely no idea how to do this. Maybe with
hook_search_api_solr_query_alter()
But I did not find documentation how to use it. Please hint me in the right direction.