Quadcap Embeddable Database

com/quadcap/sql/DeleteRow.java

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package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.BufferedOutputStream;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.OutputStream;

import java.sql.SQLException;

import com.quadcap.sql.io.ObjectInputStream;
import com.quadcap.sql.io.ObjectOutputStream;
import com.quadcap.sql.io.Extern;

import com.quadcap.sql.file.BlockAccess;
import com.quadcap.sql.file.ByteArrayRandomAccess;
import com.quadcap.sql.file.BlockFile;
import com.quadcap.sql.file.Datafile;
import com.quadcap.sql.file.Log;
import com.quadcap.sql.file.RandomAccess;
import com.quadcap.sql.file.SubPageManager;

import com.quadcap.sql.types.Value;
import com.quadcap.sql.types.ValueBlob;

import com.quadcap.util.Debug;
import com.quadcap.util.Util;

/**
 * Log step to delete a row from a table.
 *
 * @author Stan Bailes
 */
public class DeleteRow extends LogStep implements Externalizable {
    transient Table                     table;
    transient LazyRow                   row                     = null;

    byte[]                              rowBytes;
    String                              tableName               = null;
    long                                rowId                   = -1;

    /**
     * Default constructor
     */
    public DeleteRow() {}

    /**
     * Explicit constructor specifies table and row id
     */
    public DeleteRow(Session session, Table table, long rowId) {
        super(session);
        this.table = table;
        this.rowId = rowId;
        this.tableName = table.getName();
    }

    /**
     * Return the row id of the deleted row
     */
    public long getRowId() { return rowId; }

    /**
     * Get (lazy lookup) the table
     */
    final Table getTable(Database db) throws IOException {
        if (table == null) {
            table = (Table)db.getRelation(tableName);
        }
        return table;
    }

    /**
     * LogStep.redo implementation.  Delete the row (and blob refs, if
     * any)
     */
    public void redo(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        BlockFile file = db.getFile();
        getTable(db);

        if (session.getConnection().inRecovery()) {
            rowId = session.getLog().getRowMap(rowId);
        }

        db.removeRow(rowId);
        //#ifdef DEBUG
        if (Trace.bit(12)) {
            Debug.println("FREE Row " + SubPageManager.toString(rowId));
        }
        //#endif
        session.incrUpdateCount();
    }

    /**
     * LogStep.undo: Undo the row deletion by putting the old row
     * back!  (The row map is used to keep track of the fact that the
     * row may have a new row id now...)
     */
    public void undo(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        Log log = session.getLog();
        getTable(db);

        BlockFile file = db.getFile();
        long newRowId;
        if (db.inMemory()) {
            newRowId = db.putRow(session, file, getTable(db), row);
        } else {
            newRowId = file.putBytes(rowBytes);
        }
        log.putRowMap(this.rowId, newRowId);
        session.decrUpdateCount();
    }

    /**
     * Get ready to delete the row
     */
    public void prepare(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        if (db.inMemory()) {
            Table t = getTable(db);
            row = new LazyRow(t.getColumnCount());
            db.getRow(rowId, row, false);
        } else {
            BlockFile file = db.getFile();
            this.rowBytes = file.getBytes(rowId);
        }
        //#ifdef DEBUG
        if (Trace.bit(12)) {
            Debug.println("DeleteRow.prepare(): Row " +
                          SubPageManager.toString(rowId) + ": " +
                          Util.hexBytes(rowBytes));
        }
        //#endif
    }

    /**
     * Read me from a stream
     */
    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        super.readExternal(in);
        rowId = in.readLong();
        tableName = (String)in.readObject();
        int size = in.readInt();
        rowBytes = new byte[size];
        in.read(rowBytes);
    }

    /**
     * Write me to a stream
     */     
    public void writeExternal(ObjectOutput out) throws IOException {
        if (rowId == 0) {
            throw new IOException("rowId not set");
        }
        super.writeExternal(out);
        out.writeLong(rowId);
        out.writeObject(tableName);
        out.writeInt(rowBytes.length);
        out.write(rowBytes);
    }


    /**
     * My class's extern object
     */
    static Extern extern        = null;
    public void setExtern(Extern extern) { DeleteRow.extern = extern; }
    public Extern getExtern() { return extern; }    

    //#ifdef DEBUG
    /**
     * Return displayable string representation
     */
    public String toString() {
        StringBuffer sb = new StringBuffer(super.toString());
        sb.append(" DeleteRow(");
        sb.append(tableName);
        sb.append(',');
        sb.append(SubPageManager.toString(rowId));
        sb.append(')');
        return sb.toString();
    }
    //#endif
}