Quadcap Embeddable Database

com/quadcap/sql/CheckConstraint.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.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import java.sql.SQLException;

import com.quadcap.sql.types.Value;
import com.quadcap.sql.types.ValueBoolean;
import com.quadcap.sql.types.ValueUnknown;

/**
 * Constraint class for SQL <b>CHECK</b> constraints.
 *
 * @author Stan Bailes
 */
public class CheckConstraint extends Constraint implements Externalizable {
    Expression                          expression;
    
    public CheckConstraint() {}

    public CheckConstraint(String name, Expression expression) {
        super(name);
        this.expression = expression;
    }

    public void add(Session session) throws SQLException {
        if (!table.isUnderConstruction()) {
            Cursor c = table.getCursor(session, null, null);
            if (c != null) {
                try {
                    while (c.next()) {
                        checkValue(expression.getValue(session, c));
                    }
                } finally {
                    c.close();
                }
            }
        }
    }
    
    public void delete(Session session) {}
    public void undoDelete(Session session) {}

    public void applyInsert(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }
    
    public void applyDelete(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    public final void checkValue(Value val) throws SQLException {
        if (!(val instanceof ValueBoolean)) {
            if (val instanceof ValueUnknown) return;
            throw new SQLException("Bad check expression: " + expression +
                                   ", value = " + val, "42000");
        }
        if (!((ValueBoolean)val).isTrue()) {
            throw new SQLException("Check constraint violated: " +
                                   expression, "23000");
        }
    }
    
    public void checkInsert(Session session, Row row)
        throws SQLException, IOException
    {
        StaticCursor cursor = new StaticCursor(session, table, row);
        cursor.next();
        checkValue(expression.getValue(session, cursor));
    }

    public void checkUpdate(Session session, byte[] oldKey, Row row,
                            Row oldRow, long rowId, Constraint activeIndex)
        throws SQLException, IOException
    {
        checkInsert(session, row);
    }
    
    public void checkDelete(Session session, Row row, long rowId)
        throws SQLException, IOException
    {
    }
    
    public void applyUpdate(Session session, byte[] oldKey, Row row,
                            Row oldRow, long rowId, Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        super.readExternal(in);
        expression = (Expression)in.readObject();
    }
    
    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);
        out.writeObject(expression);
    }
}