[fix #623] region may be missed (#624)

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

@@ -75,9 +75,13 @@ public class ConcreteScanIterator extends ScanIterator {
     TiRegion region;
     try (RegionStoreClient client = builder.build(startKey)) {
       client.setTimeout(conf.getScanTimeout());
-      region = client.getRegion();
       BackOffer backOffer = ConcreteBackOffer.newScannerNextMaxBackOff();
       currentCache = client.scan(backOffer, startKey, version);
+      // If we get region before scan, we will use region from cache which
+      // may have wrong end key. This may miss some regions that split from old region.
+      // Client will get the newest region during scan. So we need to
+      // update region after scan.
+      region = client.getRegion();
       return region;
     }
   }

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

@@ -57,6 +57,9 @@ public class RawScanIterator extends ScanIterator {
         } else {
           try {
             currentCache = client.rawScan(backOffer, startKey, limit, keyOnly);
+            // Client will get the newest region during scan. So we need to
+            // update region after scan.
+            region = client.getRegion();
           } catch (final TiKVException e) {
             backOffer.doBackOff(BackOffFunction.BackOffFuncType.BoRegionMiss, e);
             continue;

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

@@ -65,6 +65,7 @@ public abstract class ScanIterator implements Iterator<Kvrpcpb.KvPair> {
    *
    * @return TiRegion of current data loaded to cache
    * @throws GrpcException if scan still fails after backoff
+   *     <p>TODO : Add test to check it correctness
    */
   abstract TiRegion loadCurrentRegionToCache() throws GrpcException;
 

src/main/java/org/tikv/common/region/RegionStoreClient.java

@@ -339,9 +339,6 @@ public class RegionStoreClient extends AbstractRegionStoreClient {
       BackOffer backOffer, ByteString startKey, long version, boolean keyOnly) {
     boolean forWrite = false;
     while (true) {
-      // we should refresh region
-      region = regionManager.getRegionByKey(startKey, backOffer);
-
       Supplier<ScanRequest> request =
           () ->
               ScanRequest.newBuilder()
@@ -365,6 +362,10 @@ public class RegionStoreClient extends AbstractRegionStoreClient {
               version,
               forWrite);
       ScanResponse resp = callWithRetry(backOffer, TikvGrpc.getKvScanMethod(), request, handler);
+      // retry may refresh region info
+      // we need to update region after retry
+      region = regionManager.getRegionByKey(startKey, backOffer);
+
       if (isScanSuccess(backOffer, resp)) {
         return doScan(resp);
       }
@@ -1253,6 +1254,9 @@ public class RegionStoreClient extends AbstractRegionStoreClient {
               regionManager, this, resp -> resp.hasRegionError() ? resp.getRegionError() : null);
       RawScanResponse resp =
           callWithRetry(backOffer, TikvGrpc.getRawScanMethod(), factory, handler);
+      // RegionErrorHandler may refresh region cache due to outdated region info,
+      // This region need to get newest info from cache.
+      region = regionManager.getRegionByKey(key, backOffer);
       return rawScanHelper(resp);
     } finally {
       requestTimer.observeDuration();