diff --git a/processing/src/test/java/io/druid/query/aggregation/AggregationTestHelper.java b/processing/src/test/java/io/druid/query/aggregation/AggregationTestHelper.java
index 7f5649c070a..a26a7519305 100644
--- a/processing/src/test/java/io/druid/query/aggregation/AggregationTestHelper.java
+++ b/processing/src/test/java/io/druid/query/aggregation/AggregationTestHelper.java
@@ -28,7 +28,6 @@ import com.google.common.base.Suppliers;
 import com.google.common.base.Throwables;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
-import com.google.common.io.CharSource;
 import com.google.common.io.Closeables;
 import com.google.common.io.Files;
 import com.google.common.util.concurrent.ListenableFuture;
@@ -58,9 +57,11 @@ import io.druid.query.groupby.GroupByQueryRunnerFactory;
 import io.druid.segment.IndexIO;
 import io.druid.segment.IndexMerger;
 import io.druid.segment.IndexSpec;
+import io.druid.segment.QueryableIndex;
 import io.druid.segment.QueryableIndexSegment;
 import io.druid.segment.Segment;
 import io.druid.segment.incremental.IncrementalIndex;
+import io.druid.segment.incremental.IndexSizeExceededException;
 import io.druid.segment.incremental.OnheapIncrementalIndex;
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
@@ -71,7 +72,7 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -237,19 +238,57 @@ public class AggregationTestHelper
       int maxRowCount
   ) throws Exception
   {
-    try(IncrementalIndex index = new OnheapIncrementalIndex(minTimestamp, gran, metrics, deserializeComplexMetrics, maxRowCount)) {
-      while (rows.hasNext()) {
+    IncrementalIndex index = null;
+    List<File> toMerge = new ArrayList<>();
 
+    try {
+      index = new OnheapIncrementalIndex(minTimestamp, gran, metrics, deserializeComplexMetrics, maxRowCount);
+      while (rows.hasNext()) {
         Object row = rows.next();
-        if (row instanceof String && parser instanceof StringInputRowParser) {
-          //Note: this is required because StringInputRowParser is InputRowParser<ByteBuffer> as opposed to
-          //InputRowsParser<String>
-          index.add(((StringInputRowParser) parser).parse((String) row));
-        } else {
-          index.add(parser.parse(row));
+        try {
+          if (row instanceof String && parser instanceof StringInputRowParser) {
+            //Note: this is required because StringInputRowParser is InputRowParser<ByteBuffer> as opposed to
+            //InputRowsParser<String>
+            index.add(((StringInputRowParser) parser).parse((String) row));
+          } else {
+            index.add(parser.parse(row));
+          }
+        }
+        catch (IndexSizeExceededException ex) {
+          File tmp = Files.createTempDir();
+          toMerge.add(tmp);
+          IndexMerger.persist(index, tmp, null, new IndexSpec());
+          index.close();
+          index = new OnheapIncrementalIndex(minTimestamp, gran, metrics, deserializeComplexMetrics, maxRowCount);
         }
       }
-      IndexMerger.persist(index, outDir, null, new IndexSpec());
+
+      if (toMerge.size() > 0) {
+        File tmp = Files.createTempDir();
+        toMerge.add(tmp);
+        IndexMerger.persist(index, tmp, null, new IndexSpec());
+
+        List<QueryableIndex> indexes = new ArrayList<>(toMerge.size());
+        for (File file : toMerge) {
+          indexes.add(IndexIO.loadIndex(file));
+        }
+        IndexMerger.mergeQueryableIndex(indexes, metrics, outDir, new IndexSpec());
+
+        for (QueryableIndex qi : indexes) {
+          qi.close();
+        }
+      } else {
+        IndexMerger.persist(index, outDir, null, new IndexSpec());
+      }
+    }
+    finally {
+      if (index != null) {
+        index.close();
+      }
+
+      for (File file : toMerge) {
+        FileUtils.deleteDirectory(file);
+      }
     }
   }