HSQLDB example source code file (CachedDataRow.java)

This example HSQLDB source code file (CachedDataRow.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

cacheddatarow, cacheddatarow, cachedrow, hsqlexception, hsqlexception, io, ioexception, node, node, object, pointernode, pointernode, row, rowinputinterface

The HSQLDB CachedDataRow.java source code

/* Copyright (c) 2001-2008, 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;

import java.io.IOException;

import org.hsqldb.rowio.RowInputInterface;
import org.hsqldb.rowio.RowOutputInterface;

// fredt@users 20021205 - path 1.7.2 - enhancements
// fredt@users 20021215 - doc 1.7.2 - javadoc comments

/**
 * Implementation of rows for tables with memory resident indexes and
 * disk-based data, such as TEXT tables.
 *
 * @version 1.7.2
 */
class CachedDataRow extends CachedRow {

    /**
     *  Constructor for new rows.
     */
    CachedDataRow(Table t, Object[] o) throws HsqlException {

        super(t, o);

        hasDataChanged = true;
    }

    /**
     *  Constructor when read from the disk into the Cache. The link with
     *  the Nodes is made separetly.
     */
    CachedDataRow(Table t,
                  RowInputInterface in) throws IOException, HsqlException {

        tTable         = t;
        iPos           = in.getPos();
        storageSize    = in.getSize();
        oData          = in.readData(tTable.getColumnTypes());
        hasDataChanged = false;
    }

    /**
     *  As the indexes are in-memory, this passes the existing primary node
     *  for the construction of the new Row
     */
    Row getUpdatedRow() throws HsqlException {
        return tTable.getRow(iPos, nPrimaryNode);
    }

    /**
     *  Used when data is read from the disk into the Cache the first time.
     *  New Nodes are created which are then indexed.
     */
    void setNewNodes() {

        int index = tTable.getIndexCount();

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

        Node n = nPrimaryNode;

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

    /**
     *  Used when data is re-read from the disk into the Cache. The Row is
     *  already indexed so it is linked with the Node in the primary index.
     *  the Nodes is made separetly.
     */
    void setPrimaryNode(Node primary) {
        nPrimaryNode = primary;
    }

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

    /**
     *  Writes the data to disk. Unlike CachedRow, hasChanged is never set
     *  to true when changes are made to the Nodes. (Nodes are in-memory).
     *  The only time this is used is when a new Row is added to the Caches.
     */
    public void write(RowOutputInterface out) {

        out.writeSize(storageSize);
        out.writeData(oData, tTable);
        out.writeEnd();

        hasDataChanged = false;
    }

    public boolean hasChanged() {
        return hasDataChanged;
    }

    /**
     * Sets the file position for the row and registers the row with
     * the table.
     *
     * @param pos position in data file
     */
    public void setPos(int pos) {

        iPos = pos;

        Node n = nPrimaryNode;

        while (n != null) {
            ((PointerNode) n).iData = iPos;
            n                       = n.nNext;
        }
    }

    /**
     * With the current implementation of TEXT table updates and inserts,
     * the lifetime scope of this method extends until redefinition of table
     * data source or shutdown.
     *
     * @param obj the reference object with which to compare.
     * @return <code>true if this object is the same as the obj argument;
     *   <code>false otherwise.
     */
    public boolean equals(Object obj) {

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

        if (obj instanceof CachedDataRow) {
            return ((CachedDataRow) obj).iPos == iPos
                   && ((CachedDataRow) obj).tTable == tTable;
        }

        return false;
    }
}