fix bug

Signed-off-by: lance6716 <lance6716@gmail.com>

br/pkg/lightning/backend/local/local.go

@@ -1859,7 +1859,8 @@ func nextKey(key []byte) []byte {
 
 	// in tikv <= 4.x, tikv will truncate the row key, so we should fetch the next valid row key
 	// See: https://github.com/tikv/tikv/blob/f7f22f70e1585d7ca38a59ea30e774949160c3e8/components/raftstore/src/coprocessor/split_observer.rs#L36-L41
-	if tablecodec.IsRecordKey(key) {
+	// we only do this for IntHandle, which is checked by length
+	if tablecodec.IsRecordKey(key) && len(key) == tablecodec.RecordRowKeyLen {
 		tableID, handle, _ := tablecodec.DecodeRecordKey(key)
 		nextHandle := handle.Next()
 		// int handle overflow, use the next table prefix as nextKey
@@ -1869,7 +1870,7 @@ func nextKey(key []byte) []byte {
 		return tablecodec.EncodeRowKeyWithHandle(tableID, nextHandle)
 	}
 
-	// if key is an index, directly append a 0x00 to the key.
+	// for index key and CommonHandle, directly append a 0x00 to the key.
 	res := make([]byte, 0, len(key)+1)
 	res = append(res, key...)
 	res = append(res, 0)

br/pkg/lightning/backend/local/local_test.go

@@ -116,10 +116,21 @@ func TestNextKey(t *testing.T) {
 		require.NoError(t, err)
 		nextHdl, err := tidbkv.NewCommonHandle(nextKeyBytes)
 		require.NoError(t, err)
-		expectNextKey := []byte(tablecodec.EncodeRowKeyWithHandle(1, nextHdl))
-		require.Equal(t, expectNextKey, nextKey(key))
+		nextValidKey := []byte(tablecodec.EncodeRowKeyWithHandle(1, nextHdl))
+		// nextKey may return a key that can't be decoded, but it must not be larger than the valid next key.
+		require.True(t, bytes.Compare(nextKey(key), nextValidKey) <= 0, "datums: %v", datums)
 	}
 
+	// a special case that when len(string datum) % 8 == 7, nextKey twice should not panic.
+	keyBytes, err := codec.EncodeKey(stmtCtx, nil, types.NewStringDatum("1234567"))
+	require.NoError(t, err)
+	h, err := tidbkv.NewCommonHandle(keyBytes)
+	require.NoError(t, err)
+	key = tablecodec.EncodeRowKeyWithHandle(1, h)
+	nextOnce := nextKey(key)
+	// should not panic
+	_ = nextKey(nextOnce)
+
 	// dIAAAAAAAAD/PV9pgAAAAAD/AAABA4AAAAD/AAAAAQOAAAD/AAAAAAEAAAD8
 	// a index key with: table: 61, index: 1, int64: 1, int64: 1
 	a := []byte{116, 128, 0, 0, 0, 0, 0, 0, 255, 61, 95, 105, 128, 0, 0, 0, 0, 255, 0, 0, 1, 3, 128, 0, 0, 0, 255, 0, 0, 0, 1, 3, 128, 0, 0, 255, 0, 0, 0, 0, 1, 0, 0, 0, 252}

br/tests/lightning_local_backend/run.sh

@@ -40,7 +40,6 @@ run_sql 'DROP DATABASE IF EXISTS cpeng;'
 run_lightning --backend local --enable-checkpoint=1 --log-file "$TEST_DIR/lightning-local.log" --config "tests/$TEST_NAME/config.toml" -L debug
 grep -Eq "split regions.*retryable error" "$TEST_DIR/lightning-local.log"
 
-read -p 123
 # Check that everything is correctly imported
 run_sql 'SELECT count(*), sum(c) FROM cpeng.a'
 check_contains 'count(*): 4'