datafilecache.java

hsql是很有名的嵌入式数据库

/* 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;
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 * (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.Trace;
import org.hsqldb.lib.FileAccess;
import org.hsqldb.lib.FileUtil;
import org.hsqldb.lib.StopWatch;
import org.hsqldb.lib.Storage;
import org.hsqldb.lib.ZipUnzipFile;
import org.hsqldb.rowio.RowInputBinary;
import org.hsqldb.rowio.RowInputInterface;
import org.hsqldb.rowio.RowOutputBinary;
import org.hsqldb.rowio.RowOutputInterface;
import org.hsqldb.store.BitMap;

/**
 * Acts as a manager for CACHED table persistence.<p>
 *
 * This contains the top level functionality. Provides file management services
 * and access.<p>
 *
 * Rewritten for 1.8.0 together with Cache.
 *
 * @author fredt@users
 * @version 1.8.0
 * @since 1.7.2
 */
public class DataFileCache {

    private FileAccess fa;

    // flags
    public static final int FLAG_ISSAVED = 2;
    public static final int FLAG_ROWINFO = 3;

    // file format fields
    static final int LONG_EMPTY_SIZE   = 4;     // empty space size
    static final int LONG_FREE_POS_POS = 12;    // where iFreePos is saved
    static final int FLAGS_POS         = 28;
    static final int INITIAL_FREE_POS  = 32;

    //
    DataFileBlockManager     freeBlocks;
    private static final int FREE_BLOCKS_COUNT = 512;

    //
    protected String   fileName;
    protected String   backupFileName;
    protected Database database;

    // this flag is used externally to determine if a backup is required
    protected boolean fileModified;
    protected int     cacheFileScale;

    // post openning constant fields
    protected boolean cacheReadonly;

    // cache operation mode
    protected boolean storeOnInsert;

    //
    protected int     cachedRowPadding = 8;
    protected boolean hasRowInfo       = false;

    // reusable input / output streams
    protected RowInputInterface  rowIn;
    protected RowOutputInterface rowOut;

    //
    public long maxDataFileSize;

    //
    protected Storage dataFile;
    protected long    fileFreePosition;
    protected int     maxCacheSize;             // number of Rows
    protected long    maxCacheBytes;            // number of bytes
    protected Cache   cache;

    public DataFileCache(Database db, String fileName,
                         String backupName) throws HsqlException {

        this.fileName       = fileName;
        this.backupFileName = backupName;
        database            = db;
        fa                  = database.getFileAccess();

        initParams();

        cache = new Cache(this);
    }

    /**
     * initial external parameters are set here.
     */
    protected void initParams() throws HsqlException {

        int cacheScale = database.getProperties().getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_cache_scale, 14, 8, 18);
        int cacheSizeScale = database.getProperties().getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_cache_size_scale, 10, 6, 20);

        cacheFileScale = database.getProperties().getIntegerProperty(
            HsqlDatabaseProperties.hsqldb_cache_file_scale, 1);

        Trace.printSystemOut("cache_scale: " + cacheScale);
        Trace.printSystemOut("cache_size_scale: " + cacheSizeScale);

        cacheReadonly = database.isFilesReadOnly();

        int lookupTableLength = 1 << cacheScale;
        int avgRowBytes       = 1 << cacheSizeScale;

        maxCacheSize    = lookupTableLength * 3;
        maxCacheBytes   = maxCacheSize * avgRowBytes;
        maxDataFileSize = cacheFileScale == 1 ? Integer.MAX_VALUE
                                              : (long) Integer.MAX_VALUE * 8;
        dataFile        = null;
    }

    /**
     * Opens the *.data file for this cache, setting the variables that
     * allow access to the particular database version of the *.data file.
     */
    public void open(boolean readonly) throws HsqlException {

        fileFreePosition = 0;

        try {
            boolean preexists = database.isFilesInJar();
            long    freesize  = 0;

            if (!preexists && fa.isStreamElement(fileName)) {
                if (database.isStoredFileAccess()) {
                    preexists = true;
                } else {

                    // discard "empty" databases
                    File f = new File(fileName);

                    preexists = f.length() > INITIAL_FREE_POS;
                }
            }

            if (preexists) {
                String version = database.getProperties().getProperty(
                    HsqlDatabaseProperties.hsqldb_cache_version);
                boolean v17 =
                    HsqlDatabaseProperties.VERSION_STRING_1_7_0.equals(
                        version);

                // for later versions
                boolean v18 =
                    HsqlDatabaseProperties.VERSION_STRING_1_8_0.equals(
                        version);

                if (!v17) {
                    throw Trace.error(Trace.WRONG_DATABASE_FILE_VERSION);
                }
            }

            boolean isNio = database.getProperties().isPropertyTrue(
                HsqlDatabaseProperties.hsqldb_nio_data_file);
            int fileType = isNio ? ScaledRAFile.DATA_FILE_NIO
                                 : ScaledRAFile.DATA_FILE_RAF;

            if (database.isFilesInJar()) {
                fileType = ScaledRAFile.DATA_FILE_JAR;
            }

            // [e-mail] - change to file access api
            String cname =
                database.getURLProperties().getProperty("storage_class_name");
            String skey =
                database.getURLProperties().getProperty("storage_key");

            dataFile = ScaledRAFile.newScaledRAFile(fileName, readonly,
                    fileType, cname, skey);

            if (preexists) {
                dataFile.seek(FLAGS_POS);

                int flags = dataFile.readInt();

                hasRowInfo = BitMap.isSet(flags, FLAG_ROWINFO);

                dataFile.seek(LONG_EMPTY_SIZE);

                freesize = dataFile.readLong();

                dataFile.seek(LONG_FREE_POS_POS);

                fileFreePosition = dataFile.readLong();

                if (fileFreePosition < INITIAL_FREE_POS) {
                    fileFreePosition = INITIAL_FREE_POS;
                }
            } else {
                fileFreePosition = INITIAL_FREE_POS;
            }

            initBuffers();

            fileModified = false;
            freeBlocks = new DataFileBlockManager(FREE_BLOCKS_COUNT,
                                                  cacheFileScale, freesize);
        } catch (Throwable e) {
            database.logger.appLog.logContext(e);
            close(false);

            throw Trace.error(Trace.FILE_IO_ERROR, Trace.DataFileCache_open,
                              new Object[] {
                e, fileName
            });
        }
    }

    /**
     *  Parameter write indicates either an orderly close, or a fast close
     *  without backup.
     *
     *  When false, just closes the file.
     *
     *  When true, writes out all cached rows that have been modified and the free
     *  position pointer for the *.data file and then closes the file.
     */
    public void close(boolean write) throws HsqlException {

        try {
            if (cacheReadonly) {
                if (dataFile != null) {
                    dataFile.close();
                }

                return;
            }

            StopWatch sw = new StopWatch();

            if (write) {
                cache.saveAll();
                Trace.printSystemOut("saveAll: " + sw.elapsedTime());

                // set empty
                dataFile.seek(LONG_EMPTY_SIZE);
                dataFile.writeLong(freeBlocks.getLostBlocksSize());

                // set end
                dataFile.seek(LONG_FREE_POS_POS);
                dataFile.writeLong(fileFreePosition);

                // set saved flag;
                dataFile.seek(FLAGS_POS);

                int flag = BitMap.set(0, FLAG_ISSAVED);

                if (hasRowInfo) {
                    flag = BitMap.set(flag, FLAG_ROWINFO);
                }

                dataFile.writeInt(flag);

                //
                dataFile.seek(fileFreePosition);
                Trace.printSystemOut("pos and flags: " + sw.elapsedTime());
            }

            if (dataFile != null) {
                dataFile.close();

                dataFile = null;

                Trace.printSystemOut("close: " + sw.elapsedTime());
            }

            boolean empty = fileFreePosition == INITIAL_FREE_POS;

            if (empty) {
                fa.removeElement(fileName);
                fa.removeElement(backupFileName);
            }
        } catch (Throwable e) {
            database.logger.appLog.logContext(e);

            throw Trace.error(Trace.FILE_IO_ERROR, Trace.DataFileCache_close,
                              new Object[] {
                e, fileName
            });
        }
    }

    void postClose(boolean keep) throws HsqlException {

        if (cacheReadonly) {
            return;
        }

        try {
            if (keep) {
                database.getProperties().setProperty(
                    HsqlDatabaseProperties.hsqldb_cache_version,
                    HsqlDatabaseProperties.VERSION_STRING_1_7_0);
                database.getProperties().save();

                if (fileModified) {
                    backup();
                }
            } else {
                fa.removeElement(backupFileName);
                deleteOrResetFreePos(database, fileName);
            }
        } catch (IOException e) {
            throw new HsqlException(
                e, Trace.getMessage(Trace.GENERAL_IO_ERROR),
                Trace.GENERAL_IO_ERROR);
        }
    }

    protected void initBuffers() {

        if (rowOut == null
                || ((RowOutputBinary) rowOut).getBuffer().length > 256) {
            rowOut = new RowOutputBinary(256);
        }

        if (rowIn == null
                || ((RowInputBinary) rowIn).getBuffer().length > 256) {
            rowIn = new RowInputBinary(new byte[256]);
        }
    }

    /**
     *  Writes out all the rows to a new file without fragmentation.
     */
    public void defrag() throws HsqlException {

        if (cacheReadonly) {
            return;
        }

        if (fileFreePosition == INITIAL_FREE_POS) {
            return;
        }

        try {
            boolean        wasNio = dataFile.wasNio();
            DataFileDefrag dfd = new DataFileDefrag(database, this, fileName);

            dfd.process();
            close(false);