diff --git a/server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregator.java b/server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregator.java
index a37452490d1d5..0f3d975960364 100644
--- a/server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregator.java
+++ b/server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregator.java
@@ -328,6 +328,11 @@ private abstract static class Collector extends LeafBucketCollector implements R
 
     }
 
+    /**
+     * This collector enhance the delegate collector with pruning ability on term field
+     * The iterators of term field values are wrapped into a priority queue, and able to
+     * pop/prune the values after being collected
+     */
     private static class PruningCollector extends Collector {
 
         private final Collector delegate;
@@ -348,8 +353,8 @@ private static class PruningCollector extends Collector {
             }
 
             this.queue = new DisiPriorityQueue(postingMap.size());
-            for (Map.Entry<BytesRef, Scorer> entry : postingMap.entrySet()) {
-                queue.add(new DisiWrapper(entry.getValue()));
+            for (Scorer scorer : postingMap.values()) {
+                queue.add(new DisiWrapper(scorer));
             }
 
             competitiveIterator = new DisjunctionDISI(queue);
diff --git a/server/src/test/java/org/opensearch/search/aggregations/metrics/CardinalityAggregatorTests.java b/server/src/test/java/org/opensearch/search/aggregations/metrics/CardinalityAggregatorTests.java
index 1de553a960414..b5dd27e37c332 100644
--- a/server/src/test/java/org/opensearch/search/aggregations/metrics/CardinalityAggregatorTests.java
+++ b/server/src/test/java/org/opensearch/search/aggregations/metrics/CardinalityAggregatorTests.java
@@ -43,6 +43,7 @@
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.NoMergePolicy;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.DocValuesFieldExistsQuery;
 import org.apache.lucene.search.IndexSearcher;
@@ -73,6 +74,7 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Consumer;
@@ -224,6 +226,39 @@ private void testAggregation(
         testCase(aggregationBuilder, query, buildIndex, verify, fieldType);
     }
 
+    public void testDynamicPruningDisabledWhenExceedingThreshold() throws IOException {
+        final String fieldName = "testField";
+        final String filterFieldName = "filterField";
+
+        MappedFieldType fieldType = new KeywordFieldMapper.KeywordFieldType(fieldName);
+        final CardinalityAggregationBuilder aggregationBuilder = new CardinalityAggregationBuilder("_name").field(fieldName);
+
+        int randomCardinality = randomIntBetween(20, 100);
+        AtomicInteger counter = new AtomicInteger();
+
+        testDynamicPruning(aggregationBuilder, new TermQuery(new Term(filterFieldName, "foo")), iw -> {
+            for (int i = 0; i < randomCardinality; i++) {
+                String filterValue = "foo";
+                if (randomBoolean()) {
+                    filterValue = "bar";
+                    counter.getAndIncrement();
+                }
+                iw.addDocument(
+                    asList(
+                        new KeywordField(filterFieldName, filterValue, Field.Store.NO),
+                        new KeywordField(fieldName, String.valueOf(i), Field.Store.NO),
+                        new SortedSetDocValuesField(fieldName, new BytesRef(String.valueOf(i)))
+                    )
+                );
+            }
+        },
+            card -> { assertEquals(randomCardinality - counter.get(), card.getValue(), 0); },
+            fieldType,
+            10,
+            (collectCount) -> assertEquals(randomCardinality - counter.get(), (int) collectCount)
+        );
+    }
+
     public void testDynamicPruningFixedValues() throws IOException {
         final String fieldName = "testField";
         final String filterFieldName = "filterField";
@@ -356,15 +391,29 @@ public void testDynamicPruningFieldMissingInSegment() throws IOException {
         MappedFieldType fieldType = new KeywordFieldMapper.KeywordFieldType(fieldName);
         final CardinalityAggregationBuilder aggregationBuilder = new CardinalityAggregationBuilder("_name").field(fieldName);
 
+        int randomNumSegments = randomIntBetween(1, 50);
+        logger.info("Indexing [{}] segments", randomNumSegments);
+
         testDynamicPruning(aggregationBuilder, new MatchAllDocsQuery(), iw -> {
-            iw.addDocument(asList(new KeywordField(fieldName, "1", Field.Store.NO), new KeywordField(fieldName, "2", Field.Store.NO)));
-            iw.addDocument(asList(new KeywordField(fieldName, "1", Field.Store.NO), new KeywordField(fieldName, "3", Field.Store.NO)));
-            iw.addDocument(asList(new KeywordField(fieldName, "2", Field.Store.NO), new KeywordField(fieldName, "3", Field.Store.NO)));
+            for (int i = 0; i < randomNumSegments; i++) {
+                iw.addDocument(
+                    asList(
+                        new KeywordField(fieldName, String.valueOf(i), Field.Store.NO),
+                        new SortedSetDocValuesField(fieldName, new BytesRef(String.valueOf(i)))
+                    )
+                );
+                iw.commit();
+            }
+            iw.addDocument(List.of(new KeywordField(fieldName2, "100", Field.Store.NO)));
+            iw.addDocument(List.of(new KeywordField(fieldName2, "101", Field.Store.NO)));
+            iw.addDocument(List.of(new KeywordField(fieldName2, "102", Field.Store.NO)));
             iw.commit();
-            iw.addDocument(asList(new KeywordField(fieldName2, "100", Field.Store.NO)));
-            iw.addDocument(asList(new KeywordField(fieldName2, "101", Field.Store.NO)));
-            iw.addDocument(asList(new KeywordField(fieldName2, "102", Field.Store.NO)));
-        }, card -> { assertEquals(3, card.getValue(), 0); }, fieldType, 100, (collectCount) -> assertEquals(3, (int) collectCount));
+        },
+            card -> { assertEquals(randomNumSegments, card.getValue(), 0); },
+            fieldType,
+            100,
+            (collectCount) -> assertEquals(3, (int) collectCount)
+        );
     }
 
     private void testDynamicPruning(
@@ -377,7 +426,13 @@ private void testDynamicPruning(
         Consumer<Integer> verifyCollectCount
     ) throws IOException {
         try (Directory directory = newDirectory()) {
-            try (IndexWriter indexWriter = new IndexWriter(directory, new IndexWriterConfig().setCodec(TestUtil.getDefaultCodec()))) {
+            try (
+                IndexWriter indexWriter = new IndexWriter(
+                    directory,
+                    new IndexWriterConfig().setCodec(TestUtil.getDefaultCodec()).setMergePolicy(NoMergePolicy.INSTANCE)
+                )
+            ) {
+                // disable merge so segment number is same as commit times
                 buildIndex.accept(indexWriter);
             }
 
@@ -411,6 +466,7 @@ private void testDynamicPruning(
 
                 verify.accept(card);
 
+                logger.info("aggregator collect count {}", aggregator.getCollectCount().get());
                 verifyCollectCount.accept(aggregator.getCollectCount().get());
             }
         }