scanner: don't send scanner close request when region was exhausted

HBase server already close the region scanner[1] when there is no more
results to be send from that region. Therefore, it is useless to send
one more request to close the scanner.

[1] https://github.com/apache/hbase/blob/master/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RSRpcServices.java#L3698

scanner.go

@@ -240,7 +240,7 @@ func (s *scanner) update(resp *pb.ScanResponse, region hrpc.RegionInfo) {
 	}
 	if !resp.GetMoreResultsInRegion() {
 		// we are done with this region, prepare scan for next region
-		s.closeRegionScanner()
+		s.curRegionScannerID = noScannerID
 
 		// Normal Scan
 		if !s.rpc.Reversed() {

scanner_test.go

@@ -108,15 +108,12 @@ func testCallClose(scan *hrpc.Scan, c *mock.MockRPCClient, scannerID uint64,
 		group.Done()
 	}).Return(&pb.ScanResponse{}, nil).Times(1)
 }
+
 func TestScanner(t *testing.T) {
 	ctrl := test.NewController(t)
 	defer ctrl.Finish()
 	c := mock.NewMockRPCClient(ctrl)
 
-	var wg sync.WaitGroup
-	wg.Add(3)
-	defer wg.Wait()
-
 	scan, err := hrpc.NewScan(context.Background(), table, hrpc.NumberOfRows(2))
 	if err != nil {
 		t.Fatal(err)
@@ -152,8 +149,6 @@ func TestScanner(t *testing.T) {
 		Results: dup(resultsPB[1:2]),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
 	scannerID++
 
 	s, err = hrpc.NewScanRange(scan.Context(), table,
@@ -168,11 +163,6 @@ func TestScanner(t *testing.T) {
 		Results:   dup(resultsPB[2:3]),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
-	if err != nil {
-		t.Fatal(err)
-	}
 	scannerID++
 
 	s, err = hrpc.NewScanRange(scan.Context(), table, []byte("foo"), nil,
@@ -188,9 +178,6 @@ func TestScanner(t *testing.T) {
 		MoreResults: proto.Bool(false),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
-
 	var rs []*hrpc.Result
 	for {
 		r, err := scanner.Next()
@@ -600,10 +587,6 @@ func testPartialResults(t *testing.T, scan *hrpc.Scan, expected []*hrpc.Result)
 	defer ctrl.Finish()
 	c := mock.NewMockRPCClient(ctrl)
 
-	var wg sync.WaitGroup
-	wg.Add(3)
-	defer wg.Wait()
-
 	tcase := []struct {
 		region              hrpc.RegionInfo
 		results             []*pb.Result
@@ -680,11 +663,6 @@ func testPartialResults(t *testing.T, scan *hrpc.Scan, expected []*hrpc.Result)
 			MoreResultsInRegion: &partial.moreResultsInRegion,
 			Results:             partial.results,
 		}, nil).Times(1)
-
-		if partial.scanFromID {
-			// added call to close scanner
-			testCallClose(scan, c, scannerID, &wg, t)
-		}
 	}
 
 	var rs []*hrpc.Result
@@ -709,10 +687,6 @@ func TestReversedScanner(t *testing.T) {
 	defer ctrl.Finish()
 	c := mock.NewMockRPCClient(ctrl)
 
-	var wg sync.WaitGroup
-	wg.Add(3)
-	defer wg.Wait()
-
 	ctx := context.Background()
 	scan, err := hrpc.NewScan(ctx, table, hrpc.Reversed())
 	if err != nil {
@@ -734,9 +708,6 @@ func TestReversedScanner(t *testing.T) {
 		Results:   dup(resultsPB[3:4]),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
-
 	s, err = hrpc.NewScanRange(ctx, table,
 		append([]byte("fon"), rowPadding...), nil, hrpc.Reversed())
 	if err != nil {
@@ -749,9 +720,6 @@ func TestReversedScanner(t *testing.T) {
 		Results:   dup(resultsPB[2:3]),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
-
 	s, err = hrpc.NewScanRange(ctx, table,
 		append([]byte("baq"), rowPadding...), nil, hrpc.Reversed())
 	if err != nil {
@@ -777,9 +745,6 @@ func TestReversedScanner(t *testing.T) {
 		Results: dup(resultsPB[:1]),
 	}, nil).Times(1)
 
-	// added call to close scanner
-	testCallClose(scan, c, scannerID, &wg, t)
-
 	var rs []*hrpc.Result
 	for {
 		r, err := scanner.Next()