SOLR-25 - change FunctionQuery to use ComplexExplanation

git-svn-id: https://svn.apache.org/repos/asf/incubator/solr/trunk@452973 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -70,6 +70,9 @@ Changes in runtime behavior
     with that name does not exist. (hossman, SOLR-43)
  6. The DisMaxRequestHandler now supports multiple occurances of the "fq"
     param. (hossman, SOLR-44)
+ 7. FunctionQuery.explain now uses ComplexExplanation to provide more
+    accurate score explanations when composed in a BooleanQuery.
+    (hossman, SOLR-25)
 
 Optimizations 
  1. getDocListAndSet can now generate both a DocList and a DocSet from a 

src/java/org/apache/solr/search/function/FunctionQuery.java

@@ -134,10 +134,9 @@ public class FunctionQuery extends Query {
     public Explanation explain(int doc) throws IOException {
       float sc = qWeight * vals.floatVal(doc);
 
-      Explanation result = new Explanation();
-      result.setDescription("FunctionQuery(" + func
-        + "), product of:");
-      result.setValue(sc);
+      Explanation result = new ComplexExplanation
+        (true, sc, "FunctionQuery(" + func + "), product of:");
+
       result.addDetail(vals.explain(doc));
       result.addDetail(new Explanation(getBoost(), "boost"));
       result.addDetail(new Explanation(weight.queryNorm,"queryNorm"));