SOLR-5616: Simplifies grouping code to use ResponseBuilder.needDocList() to determine if it needs to generate a doc list for grouped results.

solr/CHANGES.txt

@@ -76,6 +76,9 @@ Other Changes
   permission name.
  The APIs are also modified to ue 'index' as the unique identifier instead of name.
   Name is an optional attribute
  now and only to be used when specifying well-known permissions (noble)
 
+* SOLR-5616: Simplifies grouping code to use ResponseBuilder.needDocList() to determine if it needs to
+  generate a doc list for grouped results. (Steven Bower, Keith Laban, Dennis Gove)
+
 ==================  6.0.0 ==================
 
 Consult the LUCENE_CHANGES.txt file for additional, low level, changes in this release

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

@@ -82,6 +82,7 @@ public class DebugComponent extends SearchComponent
   public void prepare(ResponseBuilder rb) throws IOException
   {
     if(rb.isDebugTrack() && rb.isDistrib) {
+      rb.setNeedDocList(true);
       doDebugTrack(rb);
     }
   }

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

@@ -70,6 +70,7 @@ public class HighlightComponent extends SearchComponent implements PluginInfoIni
     SolrParams params = rb.req.getParams();
     rb.doHighlights = highlighter.isHighlightingEnabled(params);
     if(rb.doHighlights){
+      rb.setNeedDocList(true);
       String hlq = params.get(HighlightParams.Q);
       String hlparser = Objects.firstNonNull(params.get(HighlightParams.QPARSER),
                                               params.get(QueryParsing.DEFTYPE, QParserPlugin.DEFAULT_QTYPE));

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

@@ -64,6 +64,9 @@ public class MoreLikeThisComponent extends SearchComponent {
   
   @Override
   public void prepare(ResponseBuilder rb) throws IOException {
+    if (rb.req.getParams().getBool(MoreLikeThisParams.MLT, false)) {
+      rb.setNeedDocList(true);
+    }
     
   }
   

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

@@ -497,7 +497,7 @@ public class QueryComponent extends SearchComponent
           }
         }
 
-        if (rb.doHighlights || rb.isDebug() || params.getBool(MoreLikeThisParams.MLT, false)) {
+        if( rb.isNeedDocList() || rb.isDebug() ){
           // we need a single list of the returned docs
           cmd.setFlags(SolrIndexSearcher.GET_DOCLIST);
         }