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Tentackle Low-Level DBMS Layer
/*
* Tentackle - https://tentackle.org
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package org.tentackle.dbms;
import org.tentackle.log.Logger;
import org.tentackle.session.PersistenceException;
import org.tentackle.session.Session;
import org.tentackle.session.SessionUtilities;
import java.util.Map;
import java.util.WeakHashMap;
/**
* Counter to track modifications for a class/table.
* The ModificationTracker maintains a list of ModificationTally-objects, one for each tracked name.
*
* @author harald
*/
public class ModificationTally {
private static final Logger LOGGER = Logger.get(ModificationTally.class);
private final DbModificationTracker tracker; // the mod tracker
private final DbModification dbModification; // the persisted modification object
private DbObjectClassVariables clazzVar; // the classvariables if tablename belongs to a PDO, null if just a name
private Boolean isTableSerialProvided; // true if table serial is managed by table, null if not known yet
private String tableSerialTableName; // if tableSerialValid holds the tableserial's tablename
private long lastSerial; // last (known) serial for the table
private long pendingCount; // number of pending counts
private final Map sessionsInTx; // sessions running a transaction during countPending()
/**
* Creates a modification counter for a given tracked name.
*
* @param tracker the modification tracker
* @param trackedName the tracked name
*/
public ModificationTally(DbModificationTracker tracker, String trackedName) {
this.tracker = tracker;
sessionsInTx = new WeakHashMap<>(); // keys are weak! Db does not override equals!
dbModification = new DbModification(tracker.isLocalClientMode() ? null : tracker.getSession(), trackedName);
clazzVar = DbObjectClassVariables.getVariables(trackedName);
if (clazzVar == null) {
// try to load the class by its name (maybe not referenced so far)
String className = SessionUtilities.getInstance().getClassName(trackedName);
if (className != null) {
try {
// this will also register the classvariables, if any
DbUtilities.getInstance().createObject(Class.forName(className));
// try again
clazzVar = DbObjectClassVariables.getVariables(trackedName);
}
catch (ClassNotFoundException | RuntimeException ex) {
LOGGER.fine("not a PDO class", ex);
}
}
}
if (clazzVar == null) {
LOGGER.info("counter created for {0} not assigned to any class variable", trackedName);
}
else {
LOGGER.info("counter created for {0} assigned to class variable {1}", trackedName, clazzVar);
}
}
/**
* Gets the modification PO.
*
* @return the modification PO
*/
public DbModification getDbModification() {
return dbModification;
}
/**
* Gets the ID of the counter.
*
* @return the unique id
*/
public long getId() {
return dbModification.getId();
}
/**
* Adds a pending count.
*
* @param session the session persisting the modification, null if thread-local session
*/
public synchronized void countPending(Session session) {
if (session == null) {
session = Session.getCurrentSession();
if (session == null) {
throw new PersistenceException("no thread-local session to count modification for " + dbModification);
}
}
if (session.isRemote()) {
throw new PersistenceException(session, "modification counting not allowed for remote sessions");
}
if (session.isTxRunning() && !tracker.isLocalClientMode()) {
sessionsInTx.putIfAbsent(session, null);
}
++pendingCount;
}
/**
* Gets the pending count.
*
* @return the pending count, 0 if none
*/
public synchronized long getPendingCount() {
return pendingCount;
}
/**
* Sets the last serial.
*
* @param lastSerial the serial
*/
public synchronized void setLastSerial(long lastSerial) {
this.lastSerial = lastSerial;
}
/**
* Gets the latest serial updated by this counter.
*
* @return the latest serial from last update plus pending count
*/
public synchronized long getLatestSerial() {
return lastSerial + pendingCount;
}
/**
* Performs the physical pending count if pending count > 0.
*/
public synchronized void performPendingCount() {
if (pendingCount > 0) {
// don't flush to database because listeners could be triggered that may not see the uncommitted data
// committed
sessionsInTx.keySet().removeIf(session -> !session.isTxRunning());
if (sessionsInTx.isEmpty()) {
LOGGER.fine("increment serial for {0} by {1}", dbModification, pendingCount);
if (dbModification.countModification(pendingCount) != 2) {
// probably the record doesn't exist? create it!
dbModification.addToModificationTable(clazzVar != null, getTableSerialTableName());
// try again
if (dbModification.countModification(pendingCount) != 2) {
throw new PersistenceException(dbModification, "updating modification count failed");
}
}
lastSerial += pendingCount;
pendingCount = 0;
}
}
}
/**
* Adds this counter to the modification table.
*/
public void addToModificationTable() {
dbModification.addToModificationTable(clazzVar != null, getTableSerialTableName());
setLastSerial(getModificationCount());
}
/**
* Get the current modification count by tablename.
*
* @return the modification count
*/
public long getModificationCount() {
return dbModification.refresh();
}
/**
* Determines whether table serial is valid for this pdo class.
*
* @return the tablename holding the tableserial, null if no tableserial
*/
private synchronized String getTableSerialTableName() {
if (isTableSerialProvided == null) { // not known yet
isTableSerialProvided = false;
if (clazzVar != null) {
tableSerialTableName = DbUtilities.getInstance().determineTableSerialTableName(clazzVar);
if (tableSerialTableName != null) {
isTableSerialProvided = true;
}
}
}
return tableSerialTableName;
}
}