function_score: remove explanation of query score from functions

The score is explained already, it should not be again explained per function.

Also, remove explanation from parameter list of ScoreFunction#explainScore()
and leave only the score.

This also removes ExplainableSearchScript which is not used anywhere and
was the only reason to have the Explanation in the parameter anyway.

closes #7245

src/main/java/org/elasticsearch/common/lucene/search/function/BoostScoreFunction.java

@@ -49,7 +49,7 @@ public class BoostScoreFunction extends ScoreFunction {
     }
 
     @Override
-    public Explanation explainScore(int docId, Explanation subQueryExpl) {
+    public Explanation explainScore(int docId, float subQueryScore) {
         Explanation exp = new Explanation(boost, "static boost factor");
         exp.addDetail(new Explanation(boost, "boostFactor"));
         return exp;

src/main/java/org/elasticsearch/common/lucene/search/function/FieldValueFactorFunction.java

@@ -70,14 +70,13 @@ public class FieldValueFactorFunction extends ScoreFunction {
     }
 
     @Override
-    public Explanation explainScore(int docId, Explanation subQueryExpl) {
+    public Explanation explainScore(int docId, float subQueryScore) {
         Explanation exp = new Explanation();
         String modifierStr = modifier != null ? modifier.toString() : "";
-        double score = score(docId, subQueryExpl.getValue());
+        double score = score(docId, subQueryScore);
         exp.setValue(CombineFunction.toFloat(score));
         exp.setDescription("field value function: " +
                 modifierStr + "(" + "doc['" + field + "'].value * factor=" + boostFactor + ")");
-        exp.addDetail(subQueryExpl);
         return exp;
     }
 

src/main/java/org/elasticsearch/common/lucene/search/function/FiltersFunctionScoreQuery.java

@@ -180,7 +180,7 @@ public class FiltersFunctionScoreQuery extends Query {
                         filterFunction.filter.getDocIdSet(context, context.reader().getLiveDocs()));
                 if (docSet.get(doc)) {
                     filterFunction.function.setNextReader(context);
-                    Explanation functionExplanation = filterFunction.function.explainScore(doc, subQueryExpl);
+                    Explanation functionExplanation = filterFunction.function.explainScore(doc, subQueryExpl.getValue());
                     double factor = functionExplanation.getValue();
                     float sc = CombineFunction.toFloat(factor);
                     ComplexExplanation filterExplanation = new ComplexExplanation(true, sc, "function score, product of:");

src/main/java/org/elasticsearch/common/lucene/search/function/FunctionScoreQuery.java

@@ -131,7 +131,7 @@ public class FunctionScoreQuery extends Query {
                 return subQueryExpl;
             }
             function.setNextReader(context);
-            Explanation functionExplanation = function.explainScore(doc, subQueryExpl);
+            Explanation functionExplanation = function.explainScore(doc, subQueryExpl.getValue());
             return combineFunction.explain(getBoost(), subQueryExpl, functionExplanation, maxBoost);
         }
     }

src/main/java/org/elasticsearch/common/lucene/search/function/RandomScoreFunction.java

@@ -44,10 +44,9 @@ public class RandomScoreFunction extends ScoreFunction {
     }
 
     @Override
-    public Explanation explainScore(int docId, Explanation subQueryExpl) {
+    public Explanation explainScore(int docId, float subQueryScore) {
         Explanation exp = new Explanation();
         exp.setDescription("random score function (seed: " + prng.originalSeed + ")");
-        exp.addDetail(subQueryExpl);
         return exp;
     }
 

src/main/java/org/elasticsearch/common/lucene/search/function/ScoreFunction.java

@@ -33,7 +33,7 @@ public abstract class ScoreFunction {
 
     public abstract double score(int docId, float subQueryScore);
 
-    public abstract Explanation explainScore(int docId, Explanation subQueryExpl);
+    public abstract Explanation explainScore(int docId, float subQueryScore);
 
     public CombineFunction getDefaultScoreCombiner() {
         return scoreCombiner;

src/main/java/org/elasticsearch/common/lucene/search/function/ScriptScoreFunction.java

@@ -22,7 +22,6 @@ package org.elasticsearch.common.lucene.search.function;
 import org.apache.lucene.index.AtomicReaderContext;
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.search.Scorer;
-import org.elasticsearch.script.ExplainableSearchScript;
 import org.elasticsearch.script.SearchScript;
 
 import java.io.IOException;
@@ -101,18 +100,14 @@ public class ScriptScoreFunction extends ScoreFunction {
     }
 
     @Override
-    public Explanation explainScore(int docId, Explanation subQueryExpl) {
+    public Explanation explainScore(int docId, float subQueryScore) {
         Explanation exp;
-        if (script instanceof ExplainableSearchScript) {
+        double score = score(docId, subQueryScore);
-            script.setNextDocId(docId);
+        String explanation = "script score function, computed with script:\"" + sScript;
-            scorer.docid = docId;
+        if (params != null) {
-            scorer.score = subQueryExpl.getValue();
+            explanation += "\" and parameters: \n" + params.toString();
-            exp = ((ExplainableSearchScript) script).explain(subQueryExpl);
-        } else {
-            double score = score(docId, subQueryExpl.getValue());
-            exp = new Explanation(CombineFunction.toFloat(score), "script score function: composed of:");
-            exp.addDetail(subQueryExpl);
         }
+        exp = new Explanation(CombineFunction.toFloat(score), explanation);
         return exp;
     }
 

src/main/java/org/elasticsearch/index/query/functionscore/DecayFunctionParser.java

@@ -455,9 +455,9 @@ public abstract class DecayFunctionParser implements ScoreFunctionParser {
         protected abstract String getFieldName();
 
         @Override
-        public Explanation explainScore(int docId, Explanation subQueryExpl) {
+        public Explanation explainScore(int docId, float subQueryScore) {
             ComplexExplanation ce = new ComplexExplanation();
-            ce.setValue(CombineFunction.toFloat(score(docId, subQueryExpl.getValue())));
+            ce.setValue(CombineFunction.toFloat(score(docId, subQueryScore)));
             ce.setMatch(true);
             ce.setDescription("Function for field " + getFieldName() + ":");
             ce.addDetail(func.explainFunction(getDistanceString(docId), distance(docId), scale));

src/main/java/org/elasticsearch/script/ExplainableSearchScript.java

@@ -1,36 +0,0 @@
-/*
- * Licensed to Elasticsearch under one or more contributor
- * license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright
- * ownership. Elasticsearch licenses this file to you under
- * the Apache License, Version 2.0 (the "License"); you may
- * not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied.  See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-
-package org.elasticsearch.script;
-
-import org.apache.lucene.search.Explanation;
-
-/**
- * To be implemented by {@link SearchScript} which can provided an {@link Explanation} of the score
- */
-public interface ExplainableSearchScript extends SearchScript {
-
-    /**
-     * Build the explanation of the current document being scored
-     * 
-     * @param subQueryExpl the explanation of the subQuery 
-     */
-    Explanation explain(Explanation subQueryExpl);
-
-}

src/main/java/org/elasticsearch/script/SearchScript.java

@@ -27,8 +27,6 @@ import java.util.Map;
 
 /**
  * A search script.
- *
- * @see {@link ExplainableSearchScript} for script which can explain a score
  */
 public interface SearchScript extends ExecutableScript, ReaderContextAware, ScorerAware {
 

src/test/java/org/elasticsearch/common/lucene/search/function/RandomScoreFunctionTests.java

@@ -183,11 +183,10 @@ public class RandomScoreFunctionTests extends ElasticsearchTestCase {
         function.score(0, 1.0f);
 
         // Generate the randomScore explanation
-        Explanation randomExplanation = function.explainScore(0, subExplanation);
+        Explanation randomExplanation = function.explainScore(0, subExplanation.getValue());
 
         // Original seed should be there
         assertThat(randomExplanation.getDescription(), containsString("" + seed));
-        assertThat(randomExplanation.getDetails(), arrayContaining(subExplanation));
     }
 
 

src/test/java/org/elasticsearch/search/functionscore/FunctionScoreTests.java

@@ -0,0 +1,90 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.search.functionscore;
+
+import org.elasticsearch.action.search.SearchResponse;
+import org.elasticsearch.action.search.SearchType;
+import org.elasticsearch.test.ElasticsearchIntegrationTest;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.concurrent.ExecutionException;
+
+import static org.elasticsearch.client.Requests.searchRequest;
+import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
+import static org.elasticsearch.index.query.QueryBuilders.functionScoreQuery;
+import static org.elasticsearch.index.query.QueryBuilders.termQuery;
+import static org.elasticsearch.index.query.functionscore.ScoreFunctionBuilders.*;
+import static org.elasticsearch.search.builder.SearchSourceBuilder.searchSource;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.greaterThan;
+
+public class FunctionScoreTests extends ElasticsearchIntegrationTest {
+
+    @Test
+    public void testExplainQueryOnlyOnce() throws IOException, ExecutionException, InterruptedException {
+        assertAcked(prepareCreate("test").addMapping(
+                "type1",
+                jsonBuilder().startObject().startObject("type1").startObject("properties").startObject("test").field("type", "string")
+                        .endObject().startObject("num").field("type", "float").endObject().endObject().endObject().endObject()));
+        ensureYellow();
+
+        client().prepareIndex()
+                .setType("type1")
+                .setId("1")
+                .setIndex("test")
+                .setSource(
+                        jsonBuilder().startObject().field("test", "value").field("num", 10).endObject()).get();
+        refresh();
+
+        SearchResponse response = client().search(
+                searchRequest().searchType(SearchType.QUERY_THEN_FETCH).source(
+                        searchSource().explain(true).query(
+                                functionScoreQuery(termQuery("test", "value")).add(gaussDecayFunction("num", 5, 5)).add(exponentialDecayFunction("num", 5, 5)).add(linearDecayFunction("num", 5, 5))))).get();
+        String explanation = response.getHits().getAt(0).explanation().toString();
+
+        checkQueryExplanationAppearsOnlyOnce(explanation);
+        response = client().search(
+                searchRequest().searchType(SearchType.QUERY_THEN_FETCH).source(
+                        searchSource().explain(true).query(
+                                functionScoreQuery(termQuery("test", "value")).add(fieldValueFactorFunction("num"))))).get();
+        explanation = response.getHits().getAt(0).explanation().toString();
+        checkQueryExplanationAppearsOnlyOnce(explanation);
+
+        response = client().search(
+                searchRequest().searchType(SearchType.QUERY_THEN_FETCH).source(
+                        searchSource().explain(true).query(
+                                functionScoreQuery(termQuery("test", "value")).add(randomFunction(10))))).get();
+        explanation = response.getHits().getAt(0).explanation().toString();
+
+        checkQueryExplanationAppearsOnlyOnce(explanation);
+    }
+
+    private void checkQueryExplanationAppearsOnlyOnce(String explanation) {
+        // use some substring of the query explanation and see if it appears twice
+        String queryExplanation = "idf(docFreq=1, maxDocs=1)";
+        int queryExplanationIndex = explanation.indexOf(queryExplanation, 0);
+        assertThat(queryExplanationIndex, greaterThan(-1));
+        queryExplanationIndex = explanation.indexOf(queryExplanation, queryExplanationIndex + 1);
+        assertThat(queryExplanationIndex, equalTo(-1));
+    }
+
+}