oracle.kv
Class Version

java.lang.Object
  oracle.kv.Version

All Implemented Interfaces:

oracle.kv.impl.util.FastExternalizable

public class Version
extends Object
implements oracle.kv.impl.util.FastExternalizable

A Version refers to a specific version of a key-value pair.

When a key-value pair is initially inserted in the KV Store, and each time it is updated, it is assigned a unique version token. The version is always returned by the put method, for example, put, and is also returned by get methods, for example, get. The version is important for two reasons:

1. When an update or delete is to be performed, it may be important to only perform the update or delete if the last known value has not changed. For example, if an integer field in a previously known value is to be incremented, it is important that the previous value has not changed in the KV Store since it was obtained by the client. This can be guaranteed by passing the version of the previously known value to the putIfVersion or deleteIfVersion method. If the version specified does not match the current version of the value in the KV Store, these methods will not perform the update or delete operation and will return an indication of failure. Optionally, they will also return the current version and/or value so the client can retry the operation or take a different action.
2. When a client reads a value that was previously written, it may be important to ensure that the KV Store node servicing the read operation has been updated with the information previously written. This can be accomplished by passing the version of the previously written value as a Consistency parameter to the read operation, for example, get. See Consistency.Version for more information.

It is important to be aware that the system may infrequently assign a new Version to a key-value pair, for example, when migrating data for better resource usage. Therefore, when using the putIfVersion or deleteIfVersion methods, one cannot assume that the Version will remain constant until it is changed by the application.

Method Summary

boolean	equals(Object other)
static Version	fromByteArray(byte[] keyBytes) Deserializes the given bytes that were returned earlier by toByteArray() and returns the resulting Version.
long	getVersion() For an implied Key associated with this Version, returns a unique identifier for this Version.
int	hashCode()
byte[]	toByteArray() Returns this Version as a serialized byte array, such that fromByteArray(byte[]) may be used to reconstitute the Version.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface oracle.kv.impl.util.FastExternalizable

writeFastExternal

Method Detail

toByteArray

public byte[] toByteArray()

Returns this Version as a serialized byte array, such that fromByteArray(byte[]) may be used to reconstitute the Version.

fromByteArray

public static Version fromByteArray(byte[] keyBytes)

Deserializes the given bytes that were returned earlier by toByteArray() and returns the resulting Version.

getVersion

public long getVersion()

For an implied Key associated with this Version, returns a unique identifier for this Version.

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object