support for empty sequential doc values iterator

Signed-off-by: Sarthak Aggarwal <[email protected]>
opensearch-project · Jul 5, 2024 · 3e94f68 · 3e94f68
1 parent 786162f
commit 3e94f68
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Showing 2 changed files with 33 additions and 2 deletions.
diff --git a/server/src/main/java/org/apache/lucene/index/BaseStarTreeBuilder.java b/server/src/main/java/org/apache/lucene/index/BaseStarTreeBuilder.java
@@ -133,7 +133,7 @@ public List<MetricAggregatorInfo> generateMetricAggregatorInfos(MapperService ma
         for (Metric metric : this.starTreeField.getMetrics()) {
             for (MetricStat metricType : metric.getMetrics()) {
                 IndexNumericFieldData.NumericType numericType;
-                SequentialDocValuesIterator metricStatReader = null;
+                SequentialDocValuesIterator metricStatReader;
                 Mapper fieldMapper = mapperService.documentMapper().mappers().getMapper(metric.getField());
                 if (fieldMapper instanceof NumberFieldMapper) {
                     numericType = ((NumberFieldMapper) fieldMapper).fieldType().numericType();
@@ -145,12 +145,14 @@ public List<MetricAggregatorInfo> generateMetricAggregatorInfos(MapperService ma
                 FieldInfo metricFieldInfos = state.fieldInfos.fieldInfo(metric.getField());
                 DocValuesType metricDocValuesType = metricFieldInfos.getDocValuesType();
                 if (metricType != MetricStat.COUNT) {
-                    // Need not initialize the metric reader for COUNT metric type
+                    // Need not initialize the metric reader with relevant doc id set iterator for COUNT metric type
                     metricStatReader = starTreeDocValuesIteratorAdapter.getDocValuesIterator(
                         metricDocValuesType,
                         metricFieldInfos,
                         fieldProducerMap.get(metricFieldInfos.name)
                     );
+                } else {
+                    metricStatReader = new SequentialDocValuesIterator();
                 }
 
                 MetricAggregatorInfo metricAggregatorInfo = new MetricAggregatorInfo(

diff --git a/.../opensearch/index/compositeindex/datacube/startree/utils/SequentialDocValuesIterator.java b/.../opensearch/index/compositeindex/datacube/startree/utils/SequentialDocValuesIterator.java
@@ -14,6 +14,7 @@
 /**
  * Coordinates the reading of documents across multiple DocIdSetIterators.
  * It encapsulates a single DocIdSetIterator and maintains the latest document ID and its associated value.
+ *
  * @opensearch.experimental
  */
 @ExperimentalApi
@@ -43,6 +44,34 @@ public SequentialDocValuesIterator(DocIdSetIterator docIdSetIterator) {
         this.docIdSetIterator = docIdSetIterator;
     }
 
+    /**
+     * Creates a SequentialDocValuesIterator with an empty DocIdSetIterator.
+     *
+     */
+    public SequentialDocValuesIterator() {
+        this.docIdSetIterator = new DocIdSetIterator() {
+            @Override
+            public int docID() {
+                return NO_MORE_DOCS;
+            }
+
+            @Override
+            public int nextDoc() {
+                return NO_MORE_DOCS;
+            }
+
+            @Override
+            public int advance(int target) {
+                return NO_MORE_DOCS;
+            }
+
+            @Override
+            public long cost() {
+                return 0;
+            }
+        };
+    }
+
     /**
      * Returns the value associated with the latest document.
      *