/*
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on May 5, 2008
*/
package com.bigdata.journal;
/**
* Some static helper methods for timestamps.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public class TimestampUtility {
/**
* Formats the timestamp as a String.
*
* @param timestamp
*
* @return
*/
static public String toString(final long timestamp) {
if (timestamp == ITx.UNISOLATED)
return "unisolated";
if (timestamp == ITx.READ_COMMITTED)
return "read-committed";
if (isReadWriteTx(timestamp))
return "readWriteTX(" + timestamp + ")";
return "readOnly(" + timestamp + ")";
}
/**
* True iff the timestamp is a possible commit time (GT ZERO).
* <p>
* Note: Both read-only transactions are commit times are positive. The
* transition identifier for a read-only transaction is chosen from among
* those distinct timestamps available between the effective commit time
* requested for the read-only transaction and the next commit time on the
* database.
*
* @param timestamp
* The timestamp.
*
* @return <code>true</code> for a possible commit time or a read-only tx.
*/
static public boolean isCommitTime(final long timestamp) {
return timestamp > 0;
}
/**
* True iff the timestamp is a possible commit time (GT ZERO) -OR- a
* {@link ITx#READ_COMMITTED} request.
*
* @param timestamp
* The timestamp.
*
* @return <code>true</code> for a possible commit time, a read-only tx, or
* a {@link ITx#READ_COMMITTED} request.
*/
static public boolean isReadOnly(final long timestamp) {
// return timestamp < ITx.READ_COMMITTED;
return timestamp > 0 || timestamp == ITx.READ_COMMITTED;
}
/**
* Return <code>true</code> iff the timestamp is a possible read-write
* transaction identifier (LT ZERO).
*
* @param timestamp
* The timestamp.
*
* @return <code>true</code> iff the timestamp is a possible read-write
* transaction identifier.
*/
static public boolean isReadWriteTx(final long timestamp) {
// return timestamp > 0;
/*
* Note: timestamp != ITx.UNISOLATED is a redundant test since
*
* READ_COMMITTED == -1
*
* and
*
* UNISOLATED == 0
*/
return timestamp < ITx.READ_COMMITTED;
}
static public boolean isReadCommittedOrUnisolated(final long timestamp) {
return timestamp == ITx.READ_COMMITTED || timestamp == ITx.UNISOLATED;
}
static public boolean isReadCommitted(final long timestamp) {
return timestamp == ITx.READ_COMMITTED;
}
static public boolean isUnisolated(final long timestamp) {
return timestamp == ITx.UNISOLATED;
}
/**
* Accepts a commitTime and returns a timestamp that will be interpreted as
* a historical read (this is a NOP).
*
* @param commitTime
* The commit time from {@link IIndexStore#getLastCommitTime()},
* etc.
*
* @return The corresponding timestamp that will be interpreted as a
* historical read against the state of the database having that
* commit time.
*
* @throws IllegalArgumentException
* if <i>commitTime</i> is negative (zero is permitted for some
* edge cases).
*/
static public long asHistoricalRead(final long commitTime) {
if (commitTime < 0)
throw new IllegalArgumentException("commitTime: " + commitTime);
// return -commitTime;
return commitTime;
}
}