SOLR-13823: fix ClassCastEx in group.query when score is requested

* This makes sures score computed for standalone and distributed
  is same for group.query. This is done by using mainQuery to compute
  scores

solr/CHANGES.txt

@@ -30,7 +30,9 @@ Jetty 9.4.19.v20190610
 
 Upgrade Notes
 ---------------------
-(No changes)
+
+* org.apache.solr.search.grouping.distributed.command.QueryCommand.Builder has new method 'setMainQuery' which is used
+  to set top-level query. build() would fail if called without setting mainQuery
 
 New Features
 ---------------------
@@ -64,6 +66,9 @@ Bug Fixes
 
 * SOLR-13877: Fix NPE in expand component when matched docs have fewer unique values. (Munendra S N)
 
+* SOLR-13823: Fix ClassCastEx when score is requested with group.query. This also fixes score not being generated
+  for distributed group.query case. (Uwe Jäger, Munendra S N)
+
 Other Changes
 ---------------------
 

solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java

@@ -1392,6 +1392,8 @@ public class QueryComponent extends SearchComponent
           .setSort(groupSortSpec.getSort())
           .setQuery(query, rb.req)
           .setDocSet(searcher)
+          .setMainQuery(rb.getQuery())
+          .setNeedScores(needScores)
           .build()
       );
     }

solr/core/src/java/org/apache/solr/search/Grouping.java

@@ -887,12 +887,13 @@ public class Grouping {
 
     @Override
     protected void finish() throws IOException {
-      TopDocsCollector topDocsCollector = (TopDocsCollector) collector.getDelegate();
+      TopDocs topDocs = topCollector.topDocs();
-      TopDocs topDocs = topDocsCollector.topDocs();
       float maxScore;
       if (withinGroupSort == null || withinGroupSort.equals(Sort.RELEVANCE)) {
         maxScore = topDocs.scoreDocs.length == 0 ? Float.NaN : topDocs.scoreDocs[0].score;
       } else if (needScores) {
+        // use top-level query to populate the scores
+        TopFieldCollector.populateScores(topDocs.scoreDocs, searcher, Grouping.this.query);
         maxScore = maxScoreCollector.getMaxScore();
       } else {
         maxScore = Float.NaN;

solr/core/src/java/org/apache/solr/search/grouping/distributed/command/QueryCommand.java

@@ -16,7 +16,19 @@
  */
 package org.apache.solr.search.grouping.distributed.command;
 
-import org.apache.lucene.search.*;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.lucene.search.Collector;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.MultiCollector;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.search.Sort;
+import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.search.TopDocsCollector;
+import org.apache.lucene.search.TopFieldCollector;
+import org.apache.lucene.search.TopScoreDocCollector;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.search.DocSet;
 import org.apache.solr.search.MaxScoreCollector;
@@ -26,10 +38,6 @@ import org.apache.solr.search.SyntaxError;
 import org.apache.solr.search.grouping.Command;
 import org.apache.solr.search.grouping.collector.FilterCollector;
 
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.List;
-
 /**
  *
  */
@@ -40,6 +48,7 @@ public class QueryCommand implements Command<QueryCommandResult> {
     private Sort sort;
     private String queryString;
     private Query query;
+    private Query mainQuery;
     private DocSet docSet;
     private Integer docsToCollect;
     private boolean needScores;
@@ -49,11 +58,28 @@ public class QueryCommand implements Command<QueryCommandResult> {
       return this;
     }
 
+    /**
+     * Sets the group query.
+     *
+     * @param query The {@link Query} used for grouping
+     * @return this
+     */
     public Builder setQuery(Query query) {
       this.query = query;
       return this;
     }
 
+    /**
+     * Sets the main query used for fetching results. This is mainly used for computing the scores.
+     *
+     * @param mainQuery The top-level query
+     * @return this
+     */
+    public Builder setMainQuery(Query mainQuery) {
+      this.mainQuery = mainQuery;
+      return this;
+    }
+
     /**
      * Sets the group query from the specified groupQueryString.
      * The groupQueryString is parsed into a query.
@@ -95,11 +121,11 @@ public class QueryCommand implements Command<QueryCommandResult> {
     }
 
     public QueryCommand build() {
-      if (sort == null || query == null || docSet == null || docsToCollect == null) {
+      if (sort == null || query == null || docSet == null || docsToCollect == null || mainQuery == null) {
         throw new IllegalStateException("All fields must be set");
       }
 
-      return new QueryCommand(sort, query, docsToCollect, needScores, docSet, queryString);
+      return new QueryCommand(sort, query, docsToCollect, needScores, docSet, queryString, mainQuery);
     }
 
   }
@@ -110,19 +136,27 @@ public class QueryCommand implements Command<QueryCommandResult> {
   private final int docsToCollect;
   private final boolean needScores;
   private final String queryString;
+  private final Query mainQuery;
 
   private TopDocsCollector topDocsCollector;
   private FilterCollector filterCollector;
   private MaxScoreCollector maxScoreCollector;
   private TopDocs topDocs;
 
-  private QueryCommand(Sort sort, Query query, int docsToCollect, boolean needScores, DocSet docSet, String queryString) {
+  private QueryCommand(Sort sort,
+                       Query query,
+                       int docsToCollect,
+                       boolean needScores,
+                       DocSet docSet,
+                       String queryString,
+                       Query mainQuery) {
     this.sort = sort;
     this.query = query;
     this.docsToCollect = docsToCollect;
     this.needScores = needScores;
     this.docSet = docSet;
     this.queryString = queryString;
+    this.mainQuery = mainQuery;
   }
 
   @Override
@@ -147,7 +181,8 @@ public class QueryCommand implements Command<QueryCommandResult> {
   public void postCollect(IndexSearcher searcher) throws IOException {
     topDocs = topDocsCollector.topDocs();
     if (needScores) {
-      TopFieldCollector.populateScores(topDocs.scoreDocs, searcher, query);
+      // use mainQuery to populate the scores
+      TopFieldCollector.populateScores(topDocs.scoreDocs, searcher, mainQuery);
     }
   }
 

solr/core/src/java/org/apache/solr/search/grouping/distributed/shardresultserializer/TopGroupsResultTransformer.java

@@ -52,7 +52,7 @@ import static org.apache.solr.common.params.CommonParams.ID;
 
 /**
  * Implementation for transforming {@link TopGroups} and {@link TopDocs} into a {@link NamedList} structure and
- * visa versa.
+ * vice versa.
  */
 public class TopGroupsResultTransformer implements ShardResultTransformer<List<Command>, Map<String, ?>> {
 

solr/core/src/test/org/apache/solr/TestDistributedGrouping.java

@@ -324,6 +324,19 @@ public class TestDistributedGrouping extends BaseDistributedSearchTestCase {
     query("q", "{!func}id_i1", "rows", 100, "fl", "score,id," + i1, "group", "true", "group.field", i1, "group.limit", -1, "sort", "score desc, _docid_ asc, id asc");
     query("q", "{!func}id_i1", "rows", 100, "fl", "score,id," + i1, "group", "true", "group.field", i1, "group.limit", -1);
 
+    query("q", "*:*",
+        "group", "true",
+        "group.query", t1 + ":kings OR " + t1 + ":eggs", "group.limit", "3",
+        "fl", "id,score", "sort", i1 + " asc, id asc");
+    query("q", "*:*",
+        "group", "true",
+        "group.query", t1 + ":kings OR " + t1 + ":eggs", "group.limit", "3",
+        "fl", "id,score", "group.format", "simple", "sort", i1 + " asc, id asc");
+    query("q", "*:*",
+        "group", "true",
+        "group.query", t1 + ":kings OR " + t1 + ":eggs", "group.limit", "3",
+        "fl", "id,score", "group.main", "true", "sort", i1 + " asc, id asc");
+
     // grouping shouldn't care if there are multiple fl params, or what order the fl field names are in
     variantQuery(params("q", "*:*",
                         "group", "true", "group.field", i1dv, "group.limit", "10",

solr/core/src/test/org/apache/solr/TestGroupingSearch.java

@@ -575,6 +575,21 @@ public class TestGroupingSearch extends SolrTestCaseJ4 {
              ,"/grouped/id:1000=={'matches':10,'doclist':{'numFound':0,'start':0,'docs':[]}}"
     );
 
+    // group.query and sort
+    assertJQ(req("fq",filt,  "q","{!func}"+f2, "group","true", "group.query",f+":1", "fl","id,score", "rows","2", "group.limit","2", "sort",f+" desc, score desc", "indent","off")
+        ,"/grouped/"+f+":1==" +
+            "{'matches':10,'doclist':{'numFound':3,'start':0,'maxScore':10.0,'docs':[{'id':'8','score':10.0},{'id':'10','score':3.0}]}},"
+    );
+    // group.query with fl=score and default sort
+    assertJQ(req("fq",filt,  "q","{!func}"+f2, "group","true", "group.query",f+":1", "fl","id,score", "rows","2", "group.limit","2", "sort", "score desc", "indent","off")
+        ,"/grouped/"+f+":1==" +
+            "{'matches':10,'doclist':{'numFound':3,'start':0,'maxScore':10.0,'docs':[{'id':'8','score':10.0},{'id':'10','score':3.0}]}},"
+    );
+    assertJQ(req("fq",filt,  "q","{!func}"+f2, "group","true", "group.query",f+":1", "fl","id", "rows","2", "group.limit","2", "indent","off")
+        ,"/grouped/"+f+":1==" +
+            "{'matches':10,'doclist':{'numFound':3,'start':0,'docs':[{'id':'8'},{'id':'10'}]}},"
+    );
+
     // group.query and offset
     assertJQ(req("fq",filt,  "q","{!func}"+f2, "group","true", "group.query","id:[2 TO 5]", "fl","id", "group.limit","3", "group.offset","2")
        ,"/grouped=={'id:[2 TO 5]':{'matches':10," +