org.apache.kudu.client

Class KuduScanToken

java.lang.Object

org.apache.kudu.client.KuduScanToken

All Implemented Interfaces:

Comparable<KuduScanToken>

@InterfaceAudience.Public
 @InterfaceStability.Unstable
public class KuduScanToken
extends Object
implements Comparable<KuduScanToken>

A scan token describes a partial scan of a Kudu table limited to a single contiguous physical location. Using the KuduScanToken.KuduScanTokenBuilder, clients can describe the desired scan, including predicates, bounds, timestamps, and caching, and receive back a collection of scan tokens. Each scan token may be separately turned into a scanner using intoScanner(org.apache.kudu.client.KuduClient), with each scanner responsible for a disjoint section of the table. Scan tokens may be serialized using the serialize() method and deserialized back into a scanner using the deserializeIntoScanner(byte[], org.apache.kudu.client.KuduClient) method. This allows use cases such as generating scan tokens in the planner component of a query engine, then sending the tokens to execution nodes based on locality, and then instantiating the scanners on those nodes. Scan token locality information can be inspected using the getTablet() method.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	KuduScanToken.KuduScanTokenBuilder Builds a sequence of scan tokens.

Method Summary

Modifier and Type	Method and Description
int	compareTo(KuduScanToken other)
static KuduScanner	deserializeIntoScanner(byte[] buf, KuduClient client) Deserializes a KuduScanToken into a KuduScanner.
LocatedTablet	getTablet() Returns the tablet which the scanner created from this token will access.
KuduScanner	intoScanner(KuduClient client) Creates a KuduScanner from this scan token.
byte[]	serialize() Serializes this KuduScanToken into a byte array.
static String	stringifySerializedToken(byte[] buf, KuduClient client) Formats the serialized token for debug printing.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getTablet

public LocatedTablet getTablet()

Returns the tablet which the scanner created from this token will access.

Returns:

the located tablet

intoScanner

public KuduScanner intoScanner(KuduClient client)
                        throws Exception

Creates a KuduScanner from this scan token.

Parameters:

client - a Kudu client for the cluster

Returns:

a scanner for the scan token

Throws:

Exception

serialize

public byte[] serialize()
                 throws IOException

Serializes this KuduScanToken into a byte array.

Returns:

the serialized scan token

Throws:

IOException

deserializeIntoScanner

public static KuduScanner deserializeIntoScanner(byte[] buf,
                                                 KuduClient client)
                                          throws IOException

Deserializes a KuduScanToken into a KuduScanner.

Parameters:

buf - a byte array containing the serialized scan token.

client - a Kudu client for the cluster

Returns:

a scanner for the serialized scan token

Throws:

IOException

stringifySerializedToken

public static String stringifySerializedToken(byte[] buf,
                                              KuduClient client)
                                       throws IOException

Formats the serialized token for debug printing.

Parameters:

buf - the serialized token

client - a Kudu client for the cluster to which the token belongs

Returns:

a debug string

Throws:

IOException

compareTo

public int compareTo(KuduScanToken other)

Specified by:

compareTo in interface Comparable<KuduScanToken>