Fix flaky test in testApproximateRangeWithSizeOverDefault by adjusting totalHits assertion logic (opensearch-project#15807) (opensearch-project#16434)

- Updated the test to account for Lucene's behavior where `IndexSearcher.search()` may return `GREATER_THAN_OR_EQUAL_TO` for totalHits when the number of matches exceeds 1000.
- Added logic to check if `totalHits.relation` is `EQUAL_TO`. If so, assert that the count is exactly 11000. Otherwise, ensure the count is at least 11000 and within the allowed upper limit (`maxHits`).
- This change prevents intermittent test failures caused by Lucene’s performance optimizations.

Signed-off-by: inpink <inpink@kakao.com>

Author: inpink

CHANGELOG.md

@@ -96,6 +96,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix missing fields in task index mapping to ensure proper task result storage ([#16201](https://github.com/opensearch-project/OpenSearch/pull/16201))
 - Fix typo super->sb in method toString() of RemoteStoreNodeAttribute ([#15362](https://github.com/opensearch-project/OpenSearch/pull/15362))
 - [Workload Management] Fixing Create/Update QueryGroup TransportActions to execute from non-cluster manager nodes ([16422](https://github.com/opensearch-project/OpenSearch/pull/16422))
+- Fix flaky test in `testApproximateRangeWithSizeOverDefault` by adjusting totalHits assertion logic ([#16434](https://github.com/opensearch-project/OpenSearch/pull/16434#pullrequestreview-2386999409))
 
 ### Security
 

server/src/test/java/org/opensearch/search/approximate/ApproximatePointRangeQueryTests.java

@@ -21,6 +21,7 @@
 import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.search.TotalHits;
+import org.apache.lucene.search.TotalHits.Relation;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.tests.index.RandomIndexWriter;
 import org.opensearch.search.internal.SearchContext;
@@ -175,6 +176,7 @@ public void testApproximateRangeWithSizeOverDefault() throws IOException {
                     try {
                         long lower = 0;
                         long upper = 12000;
+                        long maxHits = 12001;
                         Query approximateQuery = new ApproximatePointRangeQuery(
                             "point",
                             pack(lower).bytes,
@@ -188,7 +190,13 @@ protected String toString(int dimension, byte[] value) {
                         };
                         IndexSearcher searcher = new IndexSearcher(reader);
                         TopDocs topDocs = searcher.search(approximateQuery, 11000);
-                        assertEquals(topDocs.totalHits, new TotalHits(11000, TotalHits.Relation.EQUAL_TO));
+
+                        if (topDocs.totalHits.relation == Relation.EQUAL_TO) {
+                            assertEquals(topDocs.totalHits.value, 11000);
+                        } else {
+                            assertTrue(11000 <= topDocs.totalHits.value);
+                            assertTrue(maxHits >= topDocs.totalHits.value);
+                        }
                     } catch (IOException e) {
                         throw new RuntimeException(e);
                     }
@@ -226,7 +234,7 @@ protected String toString(int dimension, byte[] value) {
                             }
                         };
                         Query query = LongPoint.newRangeQuery("point", lower, upper);
-                        ;
+
                         IndexSearcher searcher = new IndexSearcher(reader);
                         TopDocs topDocs = searcher.search(approximateQuery, 10);
                         TopDocs topDocs1 = searcher.search(query, 10);
@@ -235,7 +243,6 @@ protected String toString(int dimension, byte[] value) {
                         assertNotEquals(topDocs.totalHits, topDocs1.totalHits);
                         assertEquals(topDocs.totalHits, new TotalHits(10, TotalHits.Relation.EQUAL_TO));
                         assertEquals(topDocs1.totalHits, new TotalHits(101, TotalHits.Relation.EQUAL_TO));
-
                     } catch (IOException e) {
                         throw new RuntimeException(e);
                     }
@@ -278,7 +285,7 @@ protected String toString(int dimension, byte[] value) {
                             }
                         };
                         Query query = LongPoint.newRangeQuery("point", lower, upper);
-                        ;
+
                         IndexSearcher searcher = new IndexSearcher(reader);
                         Sort sort = new Sort(new SortField("point", SortField.Type.LONG));
                         TopDocs topDocs = searcher.search(approximateQuery, 10, sort);