So, I've been experimenting to learn how the _val_ participates in scores. It seems to me that http://wiki.apache.org/solr/FunctionQuery should explain the *effect* of including an _val_ term in an ordinary query, starting with a constant.
http://wiki.apache.org/solr/SolrRelevancyFAQ#How_can_I_change_the_score_of_a_document_based_on_the_.2Avalue.2A_of_a_field_.28say.2C_.22popularity.22.29 poses exactly my question, but does not explain the math. It just says, 'they get a boost'. I tried some experiments. Positive values of _val_ did lead to positive increments in the score, but clearly not by simple addition. Presumably, the brains of the operation are http://lucene.apache.org/core/old_versioned_docs/versions/3_5_0/scoring.html. However, it seems to me that it would be kind to us dumb animals if the Solr pages gave a 'for idiots' summary of the net effect. Left to my own devices, I'll eventually work my way through this, but if someone hands me a shortcut, I'll cheerfully play tech writer here and there.
