[GitHub] diegoceccarelli commented on a change in pull request #300: SOLR-11831: Skip second grouping step if group.limit is 1 (aka Las Vegas Patch)

[GitBox <gi...@apache.org>]

diegoceccarelli commented on a change in pull request #300: SOLR-11831: Skip second grouping step if group.limit is 1 (aka Las Vegas Patch)
URL: https://github.com/apache/lucene-solr/pull/300#discussion_r257259551
 
 

 ##########
 File path: solr/core/src/java/org/apache/solr/handler/component/QueryComponent.java
 ##########
 @@ -233,6 +233,41 @@ public void prepare(ResponseBuilder rb) throws IOException
     }
   }
 
+  private boolean allowSkipSecondGroupingStep(final GroupingSpecification groupingSpec, final boolean isReranking ) {
+    // Only possible if we only want one doc per group
+    if (groupingSpec.getGroupLimit() != 1) {
+        logger.error("group.skip.second.step=true is not compatible with group.limit == " + groupingSpec.getGroupLimit() );
+        return false;
+    }
+
+    // Within group sort must be the same as group sort because if we skip second step no sorting within group will be done.
+    if (groupingSpec.getSortWithinGroup() !=  groupingSpec.getGroupSort()) {
+        logger.error("group.skip.second.step=true is not compatible with group.sort != sort");
+        return false;
+    }
+
+    boolean byRelevanceOnly = false;
+    SortField[] sortFields = groupingSpec.getGroupSort().getSort();
+
+    if(sortFields != null && sortFields.length == 1 && sortFields[0] != null && sortFields[0].getComparator() instanceof FieldComparator.RelevanceComparator) {
+      byRelevanceOnly = true;
+    }
+
+    // TODO: At the moment the optimization is only supported when we are sorting by relevance only
+    if(!byRelevanceOnly) {
+        logger.error("group.skip.second.step=true is not compatible with sort= " + (sortFields != null? sortFields.toString() : null));
+        return false;
+    }
+
+    // TODO: At the moment the optimization does not support reranking
+    if(isReranking) {
 
 Review comment:
   yes! if this PR gets accepted, we will submit another one on LTR 

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