org.apache.kudu.client

Enum AsyncKuduScanner.ReadMode

java.lang.Object

java.lang.Enum<AsyncKuduScanner.ReadMode>

org.apache.kudu.client.AsyncKuduScanner.ReadMode

All Implemented Interfaces:

Serializable, Comparable<AsyncKuduScanner.ReadMode>

Enclosing class:

AsyncKuduScanner

@InterfaceAudience.Public
 @InterfaceStability.Evolving
public static enum AsyncKuduScanner.ReadMode
extends Enum<AsyncKuduScanner.ReadMode>

The possible read modes for scanners.

Enum Constant Summary

Enum Constants

Enum Constant and Description
READ_AT_SNAPSHOT When READ_AT_SNAPSHOT is specified the server will attempt to perform a read at the provided timestamp.
READ_LATEST When READ_LATEST is specified the server will always return committed writes at the time the request was received.
READ_YOUR_WRITES When @c READ_YOUR_WRITES is specified, the client will perform a read such that it follows all previously known writes and reads from this client.

Method Summary

Modifier and Type	Method and Description
static AsyncKuduScanner.ReadMode	valueOf(String name) Returns the enum constant of this type with the specified name.
static AsyncKuduScanner.ReadMode[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

READ_LATEST

public static final AsyncKuduScanner.ReadMode READ_LATEST

When READ_LATEST is specified the server will always return committed writes at the time the request was received. This type of read does not return a snapshot timestamp and is not repeatable. In ACID terms this corresponds to Isolation mode: "Read Committed" This is the default mode.

READ_AT_SNAPSHOT

public static final AsyncKuduScanner.ReadMode READ_AT_SNAPSHOT

When READ_AT_SNAPSHOT is specified the server will attempt to perform a read at the provided timestamp. If no timestamp is provided the server will take the current time as the snapshot timestamp. In this mode reads are repeatable, i.e. all future reads at the same timestamp will yield the same data. This is performed at the expense of waiting for in-flight transactions whose timestamp is lower than the snapshot's timestamp to complete, so it might incur a latency penalty. In ACID terms this, by itself, corresponds to Isolation mode "Repeatable Read". If all writes to the scanned tablet are made externally consistent, then this corresponds to Isolation mode "Strict-Serializable". Note: there currently "holes", which happen in rare edge conditions, by which writes are sometimes not externally consistent even when action was taken to make them so. In these cases Isolation may degenerate to mode "Read Committed". See KUDU-430.

READ_YOUR_WRITES

public static final AsyncKuduScanner.ReadMode READ_YOUR_WRITES

When @c READ_YOUR_WRITES is specified, the client will perform a read such that it follows all previously known writes and reads from this client. Specifically this mode: (1) ensures read-your-writes and read-your-reads session guarantees, (2) minimizes latency caused by waiting for outstanding write transactions to complete. Reads in this mode are not repeatable: two READ_YOUR_WRITES reads, even if they provide the same propagated timestamp bound, can execute at different timestamps and thus may return different results.

Method Detail

values

public static AsyncKuduScanner.ReadMode[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (AsyncKuduScanner.ReadMode c : AsyncKuduScanner.ReadMode.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static AsyncKuduScanner.ReadMode valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null