HSQLDB example source code file (CachedRow.java)

This example HSQLDB source code file (CachedRow.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - HSQLDB tags/keywords

cachedrow, cachedrow, disknode, hsqlexception, hsqlexception, io, ioexception, ioexception, no_pos, node, node, object, row, rowinputinterface, table

The HSQLDB CachedRow.java source code

/*
 * For work developed by the HSQL Development Group:
 *
 * Copyright (c) 2001-2010, 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.
 *
 *
 *
 * For work originally developed by the Hypersonic SQL Group:
 *
 * 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.
 */


package org.hsqldb;

import java.io.IOException;

import org.hsqldb.lib.IntLookup;
import org.hsqldb.lib.java.JavaSystem;
import org.hsqldb.rowio.RowInputInterface;
import org.hsqldb.rowio.RowOutputInterface;

// fredt@users 20020221 - patch 513005 by sqlbob@users (RMP)
// fredt@users 20020920 - patch 1.7.1 - refactoring to cut memory footprint
// fredt@users 20021205 - patch 1.7.2 - enhancements
// fredt@users 20021215 - doc 1.7.2 - javadoc comments
// boucherb@users - 20040411 - doc 1.7.2 - javadoc comments

/**
 *  In-memory representation of a disk-based database row object with  methods
 *  for serialization and de-serialization. <p>
 *
 *  A CachedRow is normally part of a circular double linked list which
 *  contains all of the Rows currently in the Cache for the database. It is
 *  unlinked from this list when it is freed from the Cache to make way for
 *  other rows.
 *
 *  New class from the Hypersonic Original
 *
 * @author Thomas Mueller (Hypersonic SQL Group)
 * @version    1.7.2
 * @since Hypersonic SQL
 */
public class CachedRow extends Row {

    static final int NO_POS = -1;

    //
    protected Table tTable;
    int             storageSize;

    /**
     *  Flag indicating unwritten data.
     */
    protected boolean hasDataChanged;

    /**
     *  Flag indicating Node data has changed.
     */
    boolean hasNodesChanged;

    /**
     *  Default constructor used only in subclasses.
     */
    CachedRow() {}

    public static CachedRow newCachedRow(Table t,
                                         Object[] o) throws HsqlException {

        if (t.isText) {
            return new CachedDataRow(t, o);
        } else {
            return new CachedRow(t, o);
        }
    }

    /**
     *  Constructor for new Rows.  Variable hasDataChanged is set to true in
     *  order to indicate the data needs saving.
     *
     * @param t table
     * @param o row data
     * @throws HsqlException if a database access error occurs
     */
    CachedRow(Table t, Object[] o) throws HsqlException {

        tTable = t;

        int indexcount = t.getIndexCount();

        nPrimaryNode = Node.newNode(this, 0, t);

        Node n = nPrimaryNode;

        for (int i = 1; i < indexcount; i++) {
            n.nNext = Node.newNode(this, i, t);
            n       = n.nNext;
        }

        oData          = o;
        hasDataChanged = hasNodesChanged = true;
    }

    /**
     *  Constructor when read from the disk into the Cache.
     *
     * @param t table
     * @param in data source
     * @throws IOException
     * @throws HsqlException
     */
    public CachedRow(Table t,
                     RowInputInterface in) throws IOException, HsqlException {

        tTable      = t;
        iPos        = in.getPos();
        storageSize = in.getSize();

        int indexcount = t.getIndexCount();

        nPrimaryNode = Node.newNode(this, in, 0, t);

        Node n = nPrimaryNode;

        for (int i = 1; i < indexcount; i++) {
            n.nNext = Node.newNode(this, in, i, t);
            n       = n.nNext;
        }

        oData = in.readData(tTable.getColumnTypes());
    }

    private void readRowInfo(RowInputInterface in)
    throws IOException, HsqlException {

        // for use when additional transaction info is attached to rows
    }

    /**
     *  This method is called only when the Row is deleted from the database
     *  table. The links with all the other objects apart from the data
     *  are removed.
     *
     * @throws HsqlException
     */
    public void delete() throws HsqlException {

        super.delete();

        hasNodesChanged = hasDataChanged = false;
        tTable          = null;
    }

    public int getStorageSize() {
        return storageSize;
    }

    /**
     * Sets the file position for the row
     *
     * @param pos position in data file
     */
    public void setPos(int pos) {
        iPos = pos;
    }

    /**
     * Sets flag for Node data change.
     */
    void setChanged() {
        hasNodesChanged = true;
    }

    /**
     * Returns true if Node data has changed.
     *
     * @return boolean
     */
    public boolean hasChanged() {
        return hasNodesChanged;
    }

    /**
     * Returns the Table to which this Row belongs.
     *
     * @return Table
     */
    public Table getTable() {
        return tTable;
    }

    /**
     * returned size does not include the row size written at the beginning
     */
    public int getRealSize(RowOutputInterface out) {
        return tTable.getIndexCount() * DiskNode.SIZE_IN_BYTE
               + out.getSize(this);
    }

    public void setStorageSize(int size) {
        storageSize = size;
    }

    /**
     * Returns true if any of the Nodes for this row is a root node.
     * Used only in Cache.java to avoid removing the row from the cache.
     *
     * @return boolean
     * @throws HsqlException
     */
    synchronized public boolean isKeepInMemory() {

        Node n = nPrimaryNode;

        while (n != null) {
            if (n.isRoot()) {
                return true;
            }

            n = n.nNext;
        }

        return false;
    }

    /**
     *  Using the internal reference to the Table, returns the current cached
     *  Row. Valid for deleted rows only before any subsequent insert or
     *  update on any cached table.<p>
     *
     *  Access to tables while performing the internal operations for an
     *  SQL statement result in CachedRow objects to be cleared from the cache.
     *  This method returns the CachedRow, loading it to the cache if it is not
     *  there.
     * @return the current Row in Cache for this Object
     * @throws HsqlException
     */
    synchronized Row getUpdatedRow() throws HsqlException {
        return tTable == null ? null
                              : (CachedRow) tTable.rowStore.get(iPos);
    }

    /**
     * used in CachedDataRow
     */
    void setNewNodes() {}

    /**
     *  Used exclusively by Cache to save the row to disk. New implementation
     *  in 1.7.2 writes out only the Node data if the table row data has not
     *  changed. This situation accounts for the majority of invocations as
     *  for each row deleted or inserted, the Nodes for several other rows
     *  will change.
     *
     * @param output data source
     * @throws IOException
     * @throws HsqlException
     */
    public void write(RowOutputInterface out) {

        try {
            writeNodes(out);

            if (hasDataChanged) {
                out.writeData(oData, tTable);
                out.writeEnd();

                hasDataChanged = false;
            }
        } catch (IOException e) {}
    }

    private void writeRowInfo(RowOutputInterface out) {

        // for use when additional transaction info is attached to rows
    }

    public void write(RowOutputInterface out, IntLookup lookup) {

        out.writeSize(storageSize);

        Node rownode = nPrimaryNode;

        while (rownode != null) {
            ((DiskNode) rownode).writeTranslate(out, lookup);

            rownode = rownode.nNext;
        }

        out.writeData(getData(), getTable());
        out.writeEnd();
    }

    /**
     *  Writes the Nodes, immediately after the row size.
     *
     * @param out
     *
     * @throws IOException
     * @throws HsqlException
     */
    private void writeNodes(RowOutputInterface out) throws IOException {

        out.writeSize(storageSize);

        Node n = nPrimaryNode;

        while (n != null) {
            n.write(out);

            n = n.nNext;
        }

        hasNodesChanged = false;
    }

    /**
     * With CACHED tables there may possibly exist two copies of the row.
     * All copies will have the same iPos.
     *
     * @param obj row to compare
     * @return boolean
     */
    public boolean equals(Object obj) {

        if (obj == this) {
            return true;
        }

        if (obj instanceof CachedRow) {
            return ((CachedRow) obj).iPos == iPos;
        }

        return false;
    }

    /**
     * Hash code is valid only until a modification to the cache
     *
     * @return file position of row
     */
    public int hashCode() {
        return iPos;
    }
}