/*
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 Oct 1, 2012
*/
package com.bigdata.rdf.sparql.ast.service.history;
import com.bigdata.rdf.changesets.ChangeAction;
import com.bigdata.rdf.changesets.ChangeRecord;
import com.bigdata.rdf.changesets.IChangeRecord;
import com.bigdata.rdf.spo.ISPO;
/**
* Extended to include a revision time for each record.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
public class HistoryChangeRecord extends ChangeRecord {
private final long revisionTime;
public HistoryChangeRecord(final ISPO stmt, final ChangeAction action,
final long revisionTime) {
super(stmt, action);
this.revisionTime = revisionTime;
}
public HistoryChangeRecord(final IChangeRecord changeRecord,
final long revisionTime) {
this(changeRecord.getStatement(), changeRecord.getChangeAction(),
revisionTime);
}
/**
* The revision time is <code>lastCommitTime+1</code>.
*
* TODO The revision time for the entries in the history index is currently
* <code>lastCommitTime+1</code>, but this needs to be thought through some
* more and various use cases considered.
* <p>
* The issue with revision time is that we have to record things in the
* history index incrementally, so it can not be a commit time because we do
* not have that yet. lastCommitTime+1 will always be strictly greater than
* the previous commit point. When you scan the history index, you can then
* use fromKey=firstCommitTime to visit (or null for the head of the index).
* toKey=firstCommitTime to be excluded (or null for the tail of the index).
* That all has semantics that are pretty much what people would expect for
* the scan. However, the reported revision times are not going to
* correspond directly to the commit points.
* <p>
* When reporting this data, we could resolve (and cache) the first commit
* time greater than that commit point, but only if we still have access to
* that commit point (the resolution would be against the commit record
* index, and commit points are pruned from that index when they are
* recycled).
*/
public long getRevisionTime() {
return revisionTime;
}
public String toString() {
return "revisionTime=" + revisionTime + " : " + super.toString();
}
@Override
public boolean equals(final Object o) {
if (o == this)
return true;
if (o == null || o instanceof HistoryChangeRecord == false)
return false;
final HistoryChangeRecord rec = (HistoryChangeRecord) o;
if(revisionTime != rec.getRevisionTime())
return false;
return super.equals(o);
}
}