checkpointoperation.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.store.raw.log.CheckpointOperation

   Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.impl.store.raw.log;

import org.apache.derby.iapi.services.sanity.SanityManager;
import org.apache.derby.iapi.services.io.Formatable;
import org.apache.derby.iapi.services.io.FormatIdUtil;
import org.apache.derby.iapi.services.io.StoredFormatIds;
import org.apache.derby.catalog.UUID;

import org.apache.derby.iapi.store.raw.Transaction;
import org.apache.derby.iapi.store.raw.Loggable;
import org.apache.derby.iapi.store.raw.log.LogInstant;
import org.apache.derby.iapi.store.raw.log.LogFactory;
import org.apache.derby.iapi.store.raw.xact.RawTransaction;

import org.apache.derby.iapi.error.StandardException;

import org.apache.derby.iapi.services.io.CompressedNumber;
import org.apache.derby.iapi.util.ByteArray;

import java.io.Externalizable;
import java.io.OutputStream;
import java.io.InputStream;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.IOException;
import org.apache.derby.iapi.services.io.LimitObjectInput;

/**
	A Log Operation that represents a checkpoint.
	@see Loggable
*/

public class CheckpointOperation implements Loggable 
{

	// redo LWM
	protected long	redoLWM;

	// undo LWM
	protected long	undoLWM;

	protected Formatable transactionTable;

	public CheckpointOperation(long redoLWM, long undoLWM, Formatable ttab)
	{
		this.redoLWM = redoLWM;
		this.undoLWM = undoLWM;
		this.transactionTable = ttab;
	}

	/*
	 * Formatable methods
	 */

	// no-arg constructor, required by Formatable 
	public CheckpointOperation() { super(); }

	public void writeExternal(ObjectOutput out) throws IOException 
	{
		CompressedNumber.writeLong(out, redoLWM);
		CompressedNumber.writeLong(out, undoLWM);
		// RESOLVE: Following write Not needed, keeping it to avoid upgrade/downgrade issues.
		CompressedNumber.writeInt(out, 0);	// no other truncation LWM

		if (transactionTable == null)
			CompressedNumber.writeInt(out, 0);
		else
		{
			CompressedNumber.writeInt(out, 1);
			out.writeObject(transactionTable);
		}
	}

	public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
	{
		redoLWM = CompressedNumber.readLong(in);
		undoLWM = CompressedNumber.readLong(in);

		// RESOLVE: Following read Not required, keeping it to avoid upgrade/downgrade issues.
		int tsize = CompressedNumber.readInt(in); // is there any truncationLWM?

		int haveTTab = CompressedNumber.readInt(in);
		if (haveTTab == 1)
			transactionTable = (Formatable)in.readObject();
		else
			transactionTable = (Formatable)null;
	}

	/**
		Return my format identifier.
	*/
	public int getTypeFormatId() {
		return StoredFormatIds.LOGOP_CHECKPOINT;
	}

	/**
		Loggable methods
	*/

	/**
	 *	Nothing to do unless we are rollforward recovery;
	 *  Redoing of checkpoints during rollforward recovery allows us to restart
	 *  the  roll-forward recovery from the last checkpoint redone during rollforward recovery, if
	 *  we happen to crash during the roll-forward recovery process.
	 *  Another reason why we need to do this is dropped table stub files
	 *  removed at checkpoint because the containerids may have been reused
	 *  after a checkpoint if the system was rebooted.
	*/
	public void doMe(Transaction xact, LogInstant instant, LimitObjectInput in) throws StandardException
	{
		//redo the checkpoint if we are in roll-forward recovery only
		if(((RawTransaction)xact).inRollForwardRecovery())
		{
			((RawTransaction)xact).checkpointInRollForwardRecovery(instant, redoLWM);
		}
		return;
	}

	/**
		the default for prepared log is always null for all the operations
		that don't have optionalData.  If an operation has optional data,
		the operation need to prepare the optional data for this method.

		Checkpoint has no optional data to write out
	*/
	public ByteArray getPreparedLog()
	{
		return (ByteArray) null;
	}

	/**
		Checkpoint does not need to be redone unless
		we are doing rollforward recovery.
	*/
	public boolean needsRedo(Transaction xact)
	{
		
		if(((RawTransaction)xact).inRollForwardRecovery())
			return true;
		else
			return false;
	}


	/**
	  Checkpoint has not resource to release
	*/
	public void releaseResource(Transaction xact)
	{}

	/**
		Checkpoint is a raw store operation
	*/
	public int group()
	{
		return Loggable.RAWSTORE;
	}

	/**
		Access attributes of the checkpoint record
	*/
	public long redoLWM() 
	{
		return redoLWM;
	}

	public long undoLWM() 
	{
		return undoLWM;
	}


	public Formatable getTransactionTable()
	{
		return transactionTable;
	}

	/**
	  DEBUG: Print self.
	*/
	public String toString()
	{
		if (SanityManager.DEBUG)
		{
			LogCounter undolwm = new LogCounter(undoLWM);
			LogCounter redolwm = new LogCounter(redoLWM);

			StringBuffer str = new StringBuffer(1000)
				.append("Checkpoint : \tredoLWM ")
				.append(redolwm.toString())
				.append("\n\t\tundoLWM ").append(undolwm.toString());

			if (transactionTable != null)
			{
				str.append(transactionTable.toString());
			}

			return str.toString();
		}
		else
			return null;
	}
}