rawkv: scan return 0 kv pair while exist key ByteString.EMPTY #540

Bug Report

1. Describe the bug

rawScan interface will return 0 KV-pair while there is an empty key inserted. It could be introduced by the warmup phase of client-java.

2. Minimal reproduce step (Required)

client.put(ByteString.EMPTY, ByteString.EMPTY);
System.out.println(client.scan(ByteString.EMPTY, 2).size());

3. What did you see instead (Required)

Output 1

4. What did you expect to see? (Required)

Output 0

5. What are your Java Client and TiKV versions? (Required)

• Client Java: master
• TiKV: v5.0.3