HBASE-25322 Redundant Reference file in bottom region of split

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegionFileSystem.java

@@ -681,9 +681,9 @@ public Path splitStoreFile(RegionInfo hri, String familyName, HStoreFile f, byte
       // If it is outside the range, return directly.
       f.initReader();
       try {
+        Cell splitKey = PrivateCellUtil.createFirstOnRow(splitRow);
         if (top) {
           //check if larger than last key.
-          Cell splitKey = PrivateCellUtil.createFirstOnRow(splitRow);
           Optional<Cell> lastKey = f.getLastKey();
           // If lastKey is null means storefile is empty.
           if (!lastKey.isPresent()) {
@@ -694,7 +694,6 @@ public Path splitStoreFile(RegionInfo hri, String familyName, HStoreFile f, byte
           }
         } else {
           //check if smaller than first key
-          Cell splitKey = PrivateCellUtil.createLastOnRow(splitRow);
           Optional<Cell> firstKey = f.getFirstKey();
           // If firstKey is null means storefile is empty.
           if (!firstKey.isPresent()) {

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/AssignmentTestingUtil.java

@@ -159,6 +159,11 @@ public static boolean waitForAssignment(AssignmentManager am, RegionInfo regionI
 
   public static void insertData(final HBaseTestingUtility UTIL, final TableName tableName,
     int rowCount, int startRowNum, String... cfs) throws IOException {
+    insertData(UTIL, tableName, rowCount, startRowNum, false, cfs);
+  }
+
+  public static void insertData(final HBaseTestingUtility UTIL, final TableName tableName,
+    int rowCount, int startRowNum, boolean flushOnce, String... cfs) throws IOException {
     Table t = UTIL.getConnection().getTable(tableName);
     Put p;
     for (int i = 0; i < rowCount / 2; i++) {
@@ -172,9 +177,12 @@ public static void insertData(final HBaseTestingUtility UTIL, final TableName ta
         p.addColumn(Bytes.toBytes(cf), Bytes.toBytes("q"), Bytes.toBytes(i));
       }
       t.put(p);
-      if (i % 5 == 0) {
+      if (i % 5 == 0 && !flushOnce) {
         UTIL.getAdmin().flush(tableName);
       }
     }
+    if (flushOnce) {
+      UTIL.getAdmin().flush(tableName);
+    }
   }
 }

hbase-server/src/test/java/org/apache/hadoop/hbase/master/assignment/TestRegionSplit.java

@@ -19,7 +19,9 @@
 
 import static org.apache.hadoop.hbase.master.assignment.AssignmentTestingUtil.insertData;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
+import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 import org.apache.hadoop.conf.Configuration;
@@ -28,7 +30,9 @@
 import org.apache.hadoop.hbase.ServerName;
 import org.apache.hadoop.hbase.StartMiniClusterOption;
 import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.client.Put;
 import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.Table;
 import org.apache.hadoop.hbase.client.TableDescriptor;
 import org.apache.hadoop.hbase.master.procedure.MasterProcedureEnv;
 import org.apache.hadoop.hbase.master.procedure.MasterProcedureTestingUtility;
@@ -129,7 +133,8 @@ public void testSplitTableRegion() throws Exception {
     ProcedureTestingUtility.waitProcedure(procExec, procId);
     ProcedureTestingUtility.assertProcNotFailed(procExec, procId);
 
-    assertTrue("not able to split table", UTIL.getHBaseCluster().getRegions(tableName).size() == 2);
+    assertTrue("not able to split table",
+      UTIL.getHBaseCluster().getRegions(tableName).size() == 2);
 
     //disable table
     UTIL.getAdmin().disableTable(tableName);
@@ -149,6 +154,50 @@ public void testSplitTableRegion() throws Exception {
     UTIL.getAdmin().enableTable(tableName);
     Thread.sleep(500);
 
+    assertEquals("Table region not correct.", 2,
+        UTIL.getHBaseCluster().getRegions(tableName).size());
+  }
+
+  @Test
+  public void testSplitStoreFiles() throws Exception {
+    final TableName tableName = TableName.valueOf(name.getMethodName());
+    final ProcedureExecutor<MasterProcedureEnv> procExec = getMasterProcedureExecutor();
+
+    RegionInfo[] regions = MasterProcedureTestingUtility.createTable(procExec, tableName,
+      null, columnFamilyName);
+    // flush the memstore
+    insertData(UTIL, tableName, rowCount, startRowNum, true, columnFamilyName);
+
+    // assert the hfile count of the table
+    int storeFilesCountSum = 0;
+    for(HRegion region : UTIL.getHBaseCluster().getRegions(tableName)){
+      storeFilesCountSum += region.getStore(Bytes.toBytes(columnFamilyName)).getStorefiles().size();
+    }
+    assertEquals(1, storeFilesCountSum);
+
+    // split at the start row
+    byte[] splitKey = Bytes.toBytes("" + startRowNum);
+
+    assertNotNull("Not able to find a splittable region", regions);
+    assertEquals("Not able to find a splittable region", 1, regions.length);
+
+    // Split region of the table
+    long procId = procExec.submitProcedure(
+      new SplitTableRegionProcedure(procExec.getEnvironment(), regions[0], splitKey));
+    // Wait the completion
+    ProcedureTestingUtility.waitProcedure(procExec, procId);
+    ProcedureTestingUtility.assertProcNotFailed(procExec, procId);
+
+    assertEquals("Not able to split table",
+      2, UTIL.getHBaseCluster().getRegions(tableName).size());
+
+    // assert sum of the hfiles of all regions
+    int childStoreFilesSum = 0;
+    for(HRegion region : UTIL.getHBaseCluster().getRegions(tableName)){
+      childStoreFilesSum += region.getStore(Bytes.toBytes(columnFamilyName)).getStorefiles().size();
+    }
+    assertEquals(1, childStoreFilesSum);
+
     List<HRegion> tableRegions = UTIL.getHBaseCluster().getRegions(tableName);
     assertEquals("Table region not correct.", 2, tableRegions.size());
     Map<RegionInfo, ServerName> regionInfoMap = UTIL.getHBaseCluster().getMaster()