com.bigdata.sparse
Class TimestampChooser

java.lang.Object
  com.bigdata.sparse.TimestampChooser

All Implemented Interfaces:

IRowStoreConstants

public class TimestampChooser
extends Object
implements IRowStoreConstants

Utility class for choosing timestamps for the SparseRowStore on the server.

Version:

$Id: TimestampChooser.java 2265 2009-10-26 12:51:06Z thompsonbry $

Author:

Bryan Thompson

Field Summary

Fields inherited from interface com.bigdata.sparse.IRowStoreConstants

AUTO_TIMESTAMP, AUTO_TIMESTAMP_UNIQUE, CURRENT_ROW, MAX_TIMESTAMP, MIN_TIMESTAMP

Constructor Summary

TimestampChooser()

Method Summary

static long

chooseTimestamp(IIndex ndx, long timestamp) Choose the timestamp for TPS.TPV tuples to written on the sparse row store.

Methods inherited from class java.lang.Object

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

Constructor Detail

TimestampChooser

public TimestampChooser()

Method Detail

chooseTimestamp

public static long chooseTimestamp(IIndex ndx,
                                   long timestamp)

Choose the timestamp for TPS.TPV tuples to written on the sparse row store.

Note: Revisions written with the same timestamp as a pre-existing column value will overwrite the existing column value rather than causing new revisions with their own distinct timestamp to be written. There is therefore a choice for "auto" vs "auto-unique" for timestamps.

Note: Timestamps generated locally on the server will be consistent within a row, and all revisions of column values for the same row will always be in the same index partition and hence on the same server. This means that we can use locally assigned timestamp as unique timestamps. However, time could go backwards if there is a failover to another server for the partition and the other server has a different clock time. This is resolved by choosing a timestamp assigned by the global ITimestampService.

Parameters:

timestamp - When timestamp is IRowStoreConstants.AUTO_TIMESTAMP the timestamp is the local system time. When timestamp is IRowStoreConstants.AUTO_TIMESTAMP_UNIQUE a federation wide unique timestamp is assigned by the ITimestampService. Otherwise the caller's timestamp is returned.