cherry pick tikv#541 to release-3.1

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

Author: iosmanthus

src/main/java/org/tikv/common/operation/iterator/RawScanIterator.java

@@ -28,6 +28,7 @@
 import org.tikv.kvproto.Kvrpcpb;
 
 public class RawScanIterator extends ScanIterator {
+
   private final BackOffer scanBackOffer;
 
   public RawScanIterator(
@@ -65,11 +66,12 @@ TiRegion loadCurrentRegionToCache() throws GrpcException {
     }
   }
 
-  private boolean notEndOfScan() {
-    return limit > 0
-        && !(processingLastBatch
-            && (index >= currentCache.size()
-                || Key.toRawKey(currentCache.get(index).getKey()).compareTo(endKey) >= 0));
+  private boolean endOfScan() {
+    if (!processingLastBatch) {
+      return false;
+    }
+    ByteString lastKey = currentCache.get(index).getKey();
+    return !lastKey.isEmpty() && Key.toRawKey(lastKey).compareTo(endKey) >= 0;
   }
 
   boolean isCacheDrained() {
@@ -88,7 +90,7 @@ public boolean hasNext() {
         return false;
       }
     }
-    return notEndOfScan();
+    return !endOfScan();
   }
 
   private Kvrpcpb.KvPair getCurrent() {

src/main/java/org/tikv/common/operation/iterator/ScanIterator.java

@@ -88,7 +88,7 @@ boolean cacheLoadFails() {
       Key lastKey = Key.EMPTY;
       // Session should be single-threaded itself
       // so that we don't worry about conf change in the middle
-      // of a transaction. Otherwise below code might lose data
+      // of a transaction. Otherwise, below code might lose data
       if (currentCache.size() < limit) {
         startKey = curRegionEndKey;
         lastKey = Key.toRawKey(curRegionEndKey);

src/test/java/org/tikv/raw/RawKVClientTest.java

@@ -1,14 +1,37 @@
 package org.tikv.raw;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
+import com.google.common.collect.ImmutableList;
 import com.google.protobuf.ByteString;
+<<<<<<< HEAD
 import java.io.IOException;
 import java.util.*;
 import java.util.concurrent.*;
+=======
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Random;
+import java.util.TreeMap;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorCompletionService;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+>>>>>>> 97983823c... [close #540] rawkv: fix scan return empty set while exist empty key (#541)
 import java.util.stream.Collectors;
 import org.apache.commons.lang3.RandomStringUtils;
 import org.junit.After;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.slf4j.Logger;
@@ -28,6 +51,7 @@
 import org.tikv.kvproto.Kvrpcpb;
 
 public class RawKVClientTest extends BaseRawKVTest {
+
   private static final String RAW_PREFIX = "raw_\u0001_";
   private static final int KEY_POOL_SIZE = 1000000;
   private static final int TEST_CASES = 10000;
@@ -360,6 +384,34 @@ private List<Kvrpcpb.KvPair> rawKeys() {
     return client.scan(RAW_START_KEY, RAW_END_KEY);
   }
 
+  @Test
+  public void scanTestForIssue540() {
+    ByteString splitKeyA = ByteString.copyFromUtf8("splitKeyA");
+    ByteString splitKeyB = ByteString.copyFromUtf8("splitKeyB");
+    session.splitRegionAndScatter(
+        ImmutableList.of(splitKeyA.toByteArray(), splitKeyB.toByteArray()));
+    client.deleteRange(ByteString.EMPTY, ByteString.EMPTY);
+
+    client.put(ByteString.EMPTY, ByteString.EMPTY);
+    client.put(splitKeyA, ByteString.EMPTY);
+    Assert.assertEquals(0, client.scan(ByteString.EMPTY, 0).size());
+    Assert.assertEquals(1, client.scan(ByteString.EMPTY, 1).size());
+    Assert.assertEquals(2, client.scan(ByteString.EMPTY, 2).size());
+    Assert.assertEquals(2, client.scan(ByteString.EMPTY, 3).size());
+
+    client.deleteRange(ByteString.EMPTY, ByteString.EMPTY);
+
+    client.put(ByteString.EMPTY, ByteString.EMPTY);
+    client.put(splitKeyA, ByteString.EMPTY);
+    client.put(splitKeyA.concat(ByteString.copyFromUtf8("1")), ByteString.EMPTY);
+    client.put(splitKeyA.concat(ByteString.copyFromUtf8("2")), ByteString.EMPTY);
+    client.put(splitKeyA.concat(ByteString.copyFromUtf8("3")), ByteString.EMPTY);
+    client.put(splitKeyB.concat(ByteString.copyFromUtf8("1")), ByteString.EMPTY);
+    Assert.assertEquals(6, client.scan(ByteString.EMPTY, 7).size());
+    Assert.assertEquals(0, client.scan(ByteString.EMPTY, -1).size());
+    client.deleteRange(ByteString.EMPTY, ByteString.EMPTY);
+  }
+
   @Test
   public void validate() {
     baseTest(100, 100, 100, 100, false, false, false, false, false);
@@ -449,7 +501,9 @@ private void prepare() {
       int i = cnt;
       completionService.submit(
           () -> {
-            for (int j = 0; j < base; j++) checkDelete(remainingKeys.get(i * base + j).getKey());
+            for (int j = 0; j < base; j++) {
+              checkDelete(remainingKeys.get(i * base + j).getKey());
+            }
             return null;
           });
     }
@@ -942,6 +996,7 @@ private static ByteString rawValue(String value) {
   }
 
   private static class ByteStringComparator implements Comparator<ByteString> {
+
     @Override
     public int compare(ByteString startKey, ByteString endKey) {
       return FastByteComparisons.compareTo(startKey.toByteArray(), endKey.toByteArray());