log.java

hsql是很有名的嵌入式数据库

/* Copyright (c) 1995-2000, The Hypersonic SQL Group.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the Hypersonic SQL Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE HYPERSONIC SQL GROUP,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals 
 * on behalf of the Hypersonic SQL Group.
 *
 *
 * For work added by the HSQL Development Group:
 *
 * Copyright (c) 2001-2005, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


package org.hsqldb.persist;

import java.io.File;
import java.io.IOException;

import org.hsqldb.Database;
import org.hsqldb.HsqlException;
import org.hsqldb.NumberSequence;
import org.hsqldb.Session;
import org.hsqldb.Table;
import org.hsqldb.Trace;
import org.hsqldb.lib.FileAccess;
import org.hsqldb.lib.HashMap;
import org.hsqldb.lib.Iterator;
import org.hsqldb.lib.ZipUnzipFile;
import org.hsqldb.scriptio.ScriptReaderBase;
import org.hsqldb.scriptio.ScriptWriterBase;

// fredt@users 20020215 - patch 1.7.0 by fredt
// to move operations on the database.properties files to new
// class HsqlDatabaseProperties
// fredt@users 20020220 - patch 488200 by xclayl@users - throw exception
// throw addded to all methods relying on file io
// fredt@users 20020221 - patch 513005 by sqlbob@users (RMP)
// fredt@users 20020405 - patch 1.7.0 by fredt - no change in db location
// because important information about the database is now stored in the
// *.properties file, all database files should be in the same folder as the
// *.properties file
// tony_lai@users 20020820 - export hsqldb.log_size to .properties file
// tony_lai@users 20020820 - changes to shutdown compact to save memory
// fredt@users 20020910 - patch 1.7.1 by Nitin Chauhan - code improvements
// fredt@users 20021208 - ongoing revamp
// fredt@users 20021212 - do not rewrite the *.backup file if the *.data
// file has not been updated in the current session.
// boucherb@users 20030510 - patch 1.7.2 consolidated all periodic database
// tasks in one timed task queue
// fredt@users - 20050102 patch 1.8.0 - refactoring and clearer separation of concerns

/**
 *  This class is responsible for managing the database files. An HSQLDB database
 *  consists of a .properties file, a .script file (contains an SQL script),
 *  a .data file (contains data of cached tables) a .backup file
 *  and a .log file.<p>
 *  When using TEXT tables, a data source for each table is also present.<p>
 *
 *  Notes on OpenOffice.org integration.
 *
 *  A Storage API is used when HSQLDB is integrated into OpenOffice.org. All
 *  file operations on the 4 main files are performed by OOo, which integrates
 *  the contents of these files into its database file. The script format is
 *  always TEXT in this case.
 *
 * Extensively rewritten and extended in successive versions of HSQLDB.
 *
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @author fredt@users.
 * @version 1.8.0
 * @since Hypersonic SQL
 */
public class Log {

    private HsqlDatabaseProperties properties;
    private String                 fileName;
    private Database               database;
    private FileAccess             fa;
    private ScriptWriterBase       dbLogWriter;
    private String                 scriptFileName;
    private String                 cacheFileName;
    private String                 backupFileName;
    private String                 logFileName;
    private boolean                filesReadOnly;
    private long                   maxLogSize;
    private int                    writeDelay;
    private int                    scriptFormat;
    private DataFileCache          cache;

    Log(Database db) throws HsqlException {

        database   = db;
        fa         = db.getFileAccess();
        fileName   = db.getPath();
        properties = db.getProperties();
    }

    /**
     * When opening a database, the hsqldb.compatible_version property is
     * used to determine if this version of the engine is equal to or greater
     * than the earliest version of the engine capable of opening that
     * database.<p>
     *
     * @throws  HsqlException
     */
    void open() throws HsqlException {

        // Allows the user to set log size in the properties file.
        int logMegas = properties.getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_log_size, 0);

        maxLogSize = logMegas * 1024 * 1024;
        scriptFormat = properties.getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_script_format,
            ScriptWriterBase.SCRIPT_TEXT_170);
        writeDelay     = properties.getDefaultWriteDelay();
        filesReadOnly  = database.isFilesReadOnly();
        scriptFileName = fileName + ".script";
        logFileName    = fileName + ".log";
        cacheFileName  = fileName + ".data";
        backupFileName = fileName + ".backup";

        int state = properties.getDBModified();

        switch (state) {

            case HsqlDatabaseProperties.FILES_MODIFIED :
                deleteNewAndOldFiles();
                restoreBackup();
                processScript();
                processDataFile();
                processLog();
                close(false);

                if (cache != null) {
                    cache.open(filesReadOnly);
                }

                reopenAllTextCaches();
                break;

            case HsqlDatabaseProperties.FILES_NOT_MODIFIED :

                /**
                 * if startup is after a SHUTDOWN SCRIPT and there are CACHED
                 * or TEXT tables, perform a checkpoint so that the .script
                 * file no longer contains CACHED or TEXT table rows.
                 */
                processScript();

                if (isAnyCacheModified()) {
                    close(false);

                    if (cache != null) {
                        cache.open(filesReadOnly);
                    }

                    reopenAllTextCaches();
                }
                break;

            case HsqlDatabaseProperties.FILES_NEW :
                break;
        }

        openLog();

        if (!filesReadOnly) {
            properties.setDBModified(HsqlDatabaseProperties.FILES_MODIFIED);
        }
    }

    /**
     * Close all the database files. If script argument is true, no .data
     * or .backup file will remain and the .script file will contain all the
     * data of the cached tables as well as memory tables.
     *
     * This is not used for filesReadOnly databases which use shutdown.
     */
    void close(boolean script) throws HsqlException {

        closeLog();
        deleteNewAndOldFiles();

        // create '.script.new'
        writeScript(script);
        closeAllTextCaches(script);

        if (cache != null) {
            cache.close(!script);
            cache.postClose(!script);
        }

        // [e-mail] - changed to file access api
        try {
            fa.renameElement(scriptFileName + ".new", scriptFileName);
            fa.removeElement(logFileName);
        } catch (IOException e) {
            database.logger.appLog.logContext(e);
        }

        properties.setProperty(HsqlDatabaseProperties.db_version,
                               HsqlDatabaseProperties.THIS_VERSION);
        properties.setProperty(
            HsqlDatabaseProperties.hsqldb_compatible_version,
            HsqlDatabaseProperties.FIRST_COMPATIBLE_VERSION);

        // set this one last to save the props
        properties.setDBModified(HsqlDatabaseProperties.FILES_NOT_MODIFIED);
    }

    /**
     * Fast counterpart to close(). Does not perform a checkpoint or a backup
     * of the .data file.
     */
    void shutdown() throws HsqlException {

        synchLog();

        if (cache != null) {
            cache.close(false);
        }

        closeAllTextCaches(false);
        closeLog();
    }

    /**
     * Deletes the leftovers from any previous unfinished operations.
     */
    void deleteNewAndOldFiles() {

        try {
            fa.removeElement(cacheFileName + ".old");
            fa.removeElement(cacheFileName + ".new");
            fa.removeElement(backupFileName + ".new");
            fa.removeElement(scriptFileName + ".new");
        } catch (IOException e) {
            database.logger.appLog.logContext(e);
        }
    }

    /**
     * Checks all the caches and returns true if the modified flag is set for any
     */
    boolean isAnyCacheModified() {

        if (cache != null && cache.isFileModified()) {
            return true;
        }

        return isAnyTextCacheModified();
    }

    /**
     * Performs checkpoint including pre and post operations. Returns to the
     * same state as before the checkpoint.
     */
    void checkpoint(boolean defrag) throws HsqlException {

        if (filesReadOnly) {
            return;
        }

        closeLog();
        closeAllTextCaches(false);
        reopenAllTextCaches();

        if (cache != null) {
            if (forceDefrag()) {
                defrag = true;
            }

            if (defrag) {
                try {
                    cache.defrag();
                } catch (Exception e) {
                    cache.close(true);
                    cache.postClose(true);
                    cache.open(false);
                }
            } else {
                cache.close(true);
                cache.postClose(true);
                cache.open(false);
            }
        }

        writeScript(false);

        try {
            fa.renameElement(scriptFileName + ".new", scriptFileName);
            fa.removeElement(logFileName);
        } catch (IOException e) {
            database.logger.appLog.logContext(e);
        }

        properties.setDBModified(HsqlDatabaseProperties.FILES_MODIFIED);

        if (dbLogWriter == null) {
            return;
        }

        openLog();

        Session[] sessions = database.sessionManager.getAllSessions();

        try {
            for (int i = 0; i < sessions.length; i++) {
                Session session = sessions[i];

                if (session.isAutoCommit() == false) {
                    dbLogWriter.writeLogStatement(
                        session, session.getAutoCommitStatement());
                }
            }
        } catch (IOException e) {
            throw Trace.error(Trace.FILE_IO_ERROR, logFileName);
        }
    }

    /**
     * Returns true if lost space is above the threshold
     */
    boolean forceDefrag() {

        long megas = properties.getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_defrag_limit, 200);
        long defraglimit = megas * 1024 * 1024;

        return cache.freeBlocks.getLostBlocksSize() > defraglimit;
    }

    /**
     *