This document walks you through how to use RawKV’s Scan API.

Java

Scan with limit

Using the Scan API, you can scan key-value pairs from TiKV in a range (from a startKey to an endKey).

startKey is inclusive while endKey is exclusive.

To configure the Scan API to return a limited number of key-value pairs, you can use the limit argument as in the following example code:

  1. import java.util.List;
  2. import org.tikv.common.TiConfiguration;
  3. import org.tikv.common.TiSession;
  4. import org.tikv.kvproto.Kvrpcpb;
  5. import org.tikv.raw.RawKVClient;
  6. import org.tikv.shade.com.google.protobuf.ByteString;
  8. TiConfiguration conf = TiConfiguration.createRawDefault("127.0.0.1:2379");
  9. TiSession session = TiSession.create(conf);
  10. RawKVClient client = session.createRawClient();
  12. // prepare data
  13. client.put(ByteString.copyFromUtf8("k1"), ByteString.copyFromUtf8("v1"));
  14. client.put(ByteString.copyFromUtf8("k2"), ByteString.copyFromUtf8("v2"));
  15. client.put(ByteString.copyFromUtf8("k3"), ByteString.copyFromUtf8("v3"));
  16. client.put(ByteString.copyFromUtf8("k4"), ByteString.copyFromUtf8("v4"));
  18. // scan with limit
  19. int limit = 1000;
  20. List<Kvrpcpb.KvPair> list = client.scan(ByteString.copyFromUtf8("k1"), ByteString.copyFromUtf8("k5"), limit);
  21. for(Kvrpcpb.KvPair pair : list) {
  22.     System.out.println(pair);
  23. }
  25. // close
  26. client.close();
  27. session.close();

Scan all data

The Scan API only returns a limited number of key-value pairs. If you want to fetch all the data in the range from startKey to endKey, refer to the following example code for a simple demo:

  1. import java.util.List;
  2. import org.tikv.common.TiConfiguration;
  3. import org.tikv.common.TiSession;
  4. import org.tikv.common.key.Key;
  5. import org.tikv.kvproto.Kvrpcpb;
  6. import org.tikv.raw.RawKVClient;
  7. import org.tikv.shade.com.google.protobuf.ByteString;
  9. TiConfiguration conf = TiConfiguration.createRawDefault("127.0.0.1:2379");
  10. TiSession session = TiSession.create(conf);
  11. RawKVClient client = session.createRawClient();
  13. // prepare data
  14. String keyPrefix = "p";
  15. for(int i = 1; i <= 9; i ++) {
  16.     for(int j = 1; j <= 9; j ++) {
  17.         client.put(ByteString.copyFromUtf8(keyPrefix + i + j), ByteString.copyFromUtf8("v" + i + j));
  18.     }
  19. }
  21. // scan all data
  22. ByteString startKey = ByteString.copyFromUtf8(keyPrefix + "11");
  23. ByteString endKey = Key.toRawKey(ByteString.copyFromUtf8(keyPrefix + "99")).next().toByteString();
  24. int limit = 4;
  25. while(true) {
  26.     List<Kvrpcpb.KvPair> list = client.scan(startKey, endKey, limit);
  27.     Key maxKey = Key.MIN;
  28.     for (Kvrpcpb.KvPair pair : list) {
  29.         System.out.println(pair);
  30.         Key currentKey = Key.toRawKey(pair.getKey());
  31.         if(currentKey.compareTo(maxKey) > 0) {
  32.             maxKey = currentKey;
  33.         }
  34.     }
  36.     if(list.size() < limit) {
  37.         break;
  38.     }
  39.     startKey = maxKey.next().toByteString();
  40. }

To get the example code above, click here.