store/tikv/rawkv: Add endKey support for ReverseRawScan

- ref: pingcap#8602

Signed-off-by: kamijin_fanta <kamijin@live.jp>

store/mockstore/mocktikv/rpc.go

@@ -476,22 +476,25 @@ func (h *rpcHandler) handleKvRawScan(req *kvrpcpb.RawScanRequest) *kvrpcpb.RawSc
 		}
 	}
 
-	endKey := h.endKey
-	if len(req.EndKey) > 0 && (len(endKey) == 0 || bytes.Compare(req.EndKey, endKey) < 0) {
-		endKey = req.EndKey
-	}
-
 	var pairs []Pair
 	if req.Reverse {
+		lowerBound := h.startKey
+		if len(req.EndKey) > 0 && (len(lowerBound) == 0 || bytes.Compare(req.EndKey, lowerBound) > 0) {
+			lowerBound = req.EndKey
+		}
 		pairs = rawKV.RawReverseScan(
-			req.GetStartKey(), // region start position
-			h.startKey,        // upper bound of scan
+			req.StartKey,
+			lowerBound,
 			int(req.GetLimit()),
 		)
 	} else {
+		upperBound := h.endKey
+		if len(req.EndKey) > 0 && (len(upperBound) == 0 || bytes.Compare(req.EndKey, upperBound) < 0) {
+			upperBound = req.EndKey
+		}
 		pairs = rawKV.RawScan(
-			req.GetStartKey(), // region start position
-			endKey,            // lower bound of scan
+			req.StartKey,
+			upperBound,
 			int(req.GetLimit()),
 		)
 	}

store/tikv/rawkv.go

@@ -310,9 +310,13 @@ func (c *RawKVClient) Scan(startKey, endKey []byte, limit int) (keys [][]byte, v
 	return
 }
 
-// ReverseScan queries continuous kv pairs, starts from startKey and goes backwards, up to limit pairs.
-// startKey is the exclusive upper bound. If you want to include the startKey, append a '\0' to the key
-func (c *RawKVClient) ReverseScan(startKey []byte, limit int) (keys [][]byte, values [][]byte, err error) {
+// ReverseScan queries continuous kv pairs in range [endKey, startKey), up to limit pairs.
+// Direction is different from Scan, upper to lower.
+// If endKey is empty, it means unbounded.
+// If you want to exclude the startKey or include the endKey, append a '\0' to the key. For example, to scan
+// (endKey, startKey], you can write:
+// `ReverseScan(append(startKey, '\0'), append(endKey, '\0'), limit)`.
+func (c *RawKVClient) ReverseScan(startKey, endKey []byte, limit int) (keys [][]byte, values [][]byte, err error) {
 	start := time.Now()
 	defer func() {
 		metrics.TiKVRawkvCmdHistogram.WithLabelValues("raw_reverse_scan").Observe(time.Since(start).Seconds())
@@ -327,6 +331,7 @@ func (c *RawKVClient) ReverseScan(startKey []byte, limit int) (keys [][]byte, va
 			Type: tikvrpc.CmdRawScan,
 			RawScan: &kvrpcpb.RawScanRequest{
 				StartKey: startKey,
+				EndKey:   endKey,
 				Limit:    uint32(limit - len(keys)),
 				Reverse:  true,
 			},

store/tikv/rawkv_test.go

@@ -123,7 +123,17 @@ func (s *testRawKVSuite) mustScanRange(c *C, startKey string, endKey string, lim
 }
 
 func (s *testRawKVSuite) mustReverseScan(c *C, startKey []byte, limit int, expect ...string) {
-	keys, values, err := s.client.ReverseScan(startKey, limit)
+	keys, values, err := s.client.ReverseScan(startKey, nil, limit)
+	c.Assert(err, IsNil)
+	c.Assert(len(keys)*2, Equals, len(expect))
+	for i := range keys {
+		c.Assert(string(keys[i]), Equals, expect[i*2])
+		c.Assert(string(values[i]), Equals, expect[i*2+1])
+	}
+}
+
+func (s *testRawKVSuite) mustReverseScanRange(c *C, startKey, endKey []byte, limit int, expect ...string) {
+	keys, values, err := s.client.ReverseScan(startKey, endKey, limit)
 	c.Assert(err, IsNil)
 	c.Assert(len(keys)*2, Equals, len(expect))
 	for i := range keys {
@@ -257,6 +267,9 @@ func (s *testRawKVSuite) TestReverseScan(c *C) {
 		s.mustReverseScan(c, []byte("k5"), 1, "k3", "v3")
 		s.mustReverseScan(c, append([]byte("k5"), 0), 1, "k5", "v5")
 		s.mustReverseScan(c, []byte("k6"), 3, "k5", "v5", "k3", "v3", "k1", "v1")
+
+		s.mustReverseScanRange(c, []byte("z"), []byte("k3"), 10, "k7", "v7", "k5", "v5", "k3", "v3")
+		s.mustReverseScanRange(c, []byte("k7"), append([]byte("k3"), 0), 10, "k5", "v5")
 	}
 
 	check()