Make a util method - deriveRowKeyFromScanOrRegionBoundaries

Author: Saurabh Rai

phoenix-core-server/src/main/java/org/apache/phoenix/iterate/NonAggregateRegionScannerFactory.java

@@ -83,6 +83,7 @@
 import org.apache.phoenix.util.EncodedColumnsUtil;
 import org.apache.phoenix.util.IndexUtil;
 import org.apache.phoenix.util.ScanUtil;
+import org.apache.phoenix.util.ServerUtil;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -499,23 +500,7 @@ public boolean next(List<Cell> results, ScannerContext scannerContext) throws IO
                   kv = getOffsetKvWithLastScannedRowKey(remainingOffset, tuple);
                 } else {
                   // Use fallback logic when tuple is empty (PHOENIX-7524)
-                  byte[] rowKey;
-                  byte[] startKey = scan.getStartRow().length > 0
-                    ? scan.getStartRow()
-                    : region.getRegionInfo().getStartKey();
-                  byte[] endKey = scan.getStopRow().length > 0
-                    ? scan.getStopRow()
-                    : region.getRegionInfo().getEndKey();
-                  rowKey = ByteUtil.getLargestPossibleRowKeyInRange(startKey, endKey);
-                  if (rowKey == null) {
-                    if (scan.includeStartRow()) {
-                      rowKey = startKey;
-                    } else if (scan.includeStopRow()) {
-                      rowKey = endKey;
-                    } else {
-                      rowKey = HConstants.EMPTY_END_ROW;
-                    }
-                  }
+                  byte[] rowKey = ServerUtil.deriveRowKeyFromScanOrRegionBoundaries(scan, region);
                   kv = new KeyValue(rowKey, QueryConstants.OFFSET_FAMILY,
                     QueryConstants.OFFSET_COLUMN, remainingOffset);
                 }

phoenix-core-server/src/main/java/org/apache/phoenix/util/ServerUtil.java

@@ -291,4 +291,33 @@ public static <T> Throwable getExceptionFromFailedFuture(Future<T> f) {
     }
     return t;
   }
+
+  /**
+   * Derives a safe row key for empty result sets based on scan or region boundaries. Used when
+   * constructing KeyValues for aggregate results or OFFSET responses when no actual data rows were
+   * scanned.
+   * @param scan   The scan being executed
+   * @param region The region being scanned
+   * @return A valid row key derived from scan or region boundaries
+   */
+  public static byte[] deriveRowKeyFromScanOrRegionBoundaries(Scan scan, Region region) {
+    byte[] startKey =
+      scan.getStartRow().length > 0 ? scan.getStartRow() : region.getRegionInfo().getStartKey();
+    byte[] endKey =
+      scan.getStopRow().length > 0 ? scan.getStopRow() : region.getRegionInfo().getEndKey();
+
+    byte[] rowKey = ByteUtil.getLargestPossibleRowKeyInRange(startKey, endKey);
+
+    if (rowKey == null) {
+      if (scan.includeStartRow()) {
+        rowKey = startKey;
+      } else if (scan.includeStopRow()) {
+        rowKey = endKey;
+      } else {
+        rowKey = HConstants.EMPTY_END_ROW;
+      }
+    }
+
+    return rowKey;
+  }
 }