Quadcap Embeddable Database

com/quadcap/sql/StmtUpdate.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,
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 * forth as paragraph 6 below, in the documentation and/or other materials
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 * 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.util.Vector;

import java.io.IOException;

import java.sql.ResultSet;
import java.sql.SQLException;

import com.quadcap.util.Debug;

/**
 * Implementation of the SQL <b>UPDATE</b> statement. 
 *
 * @author Stan Bailes
 */

public class StmtUpdate implements Stmt {
    String                      tableName;
    SelectExpression            select;
    Vector                      items;

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

    /**
     * Explicit constructor from table name only
     */
    public StmtUpdate(String tableName) {
        this.tableName = tableName;
        this.items = new Vector();
    }

    /**
     * Add a new update item
     */
    public void addItem(UpdateItem item) {
        items.addElement(item);
    }

    /**
     * Add a 'where' expression
     */
    public void addWhere(Expression where) {
        select = new SelectExpression(tableName, where);
    }

    /**
     * Excute the update operation
     */
    public void execute(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        Relation t = db.getRelation(tableName);
        if (t == null) {
            throw new SQLException("No such table/view: " + tableName,
                                   "42000");
        }       
        if (!t.isUpdatable()) {
            throw new SQLException("Not updatable: " + tableName,
                                   "42000");
        }
        session.getTableWriteLock(tableName);
        Cursor updateCursor = TableOps.getCursor(session, t, select);
        try {
            while (updateCursor.next()) {
                Row row = updateCursor.getRow();
                for (int i = 0; i < items.size(); i++) {
                    UpdateItem item = (UpdateItem)items.elementAt(i);
                    item.evaluate(session, t, updateCursor);
                }
                for (int i = 0; i < items.size(); i++) {
                    UpdateItem item = (UpdateItem)items.elementAt(i);
                    item.update(session, row);
                }
                session.clearViewCheck();
                updateCursor.updateRow(row);               // ZZZ hot
            }
        } finally {
            updateCursor.close();
        }
    }
}