Quadcap Embeddable Database

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

import java.util.Enumeration;
import java.util.Vector;

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

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

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

import com.quadcap.sql.index.Btree;

import com.quadcap.sql.file.BlockFile;

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

/**
 * Index constraint for indexes in which keys must be unique.
 *
 * @author Stan Bailes
 */
public class UniqueConstraint extends IndexConstraint
                              implements Externalizable
{
    Vector                              exportConstraints       = null;

    /**
     * Default constraint (required for Externalizable)
     */
    public UniqueConstraint() {}

    /**
     * Explicit constructor for named constraint
     */
    public UniqueConstraint(String name) {
        super(name);
    }

    /**
     * Explicit constructor with name and columns
     */
    public UniqueConstraint(String name, Vector names) {
        super(name, names);
    }

    /**
     * Constraint.checkInsert()  We make sure the key isn't already in
     * the index.
     *
     * XXX This implementation could be optimized if we could roll this up
     * XXX in the apply step
     */
    public void checkInsert(Session session, Row row)
        throws SQLException, IOException
    {
        Database db = session.getDatabase();       
        byte[] key = makeKey(session, row, 0);
        getIndex(db);
        if (index.get(key) != null) {
            throw new SQLException(constraintType() +
                                   " constraint violated: " + this,
                                   "23000");
        }
    }

    /**
     * IndexConstraint.Return the number of columns in this index
     */
    public int getIndexColumnCount() {
        return getColumnCount() + 1;
    }

    public byte[] makeKey(Session session, Row row, long rowId)
        throws SQLException
    {
        long discrim = 0;
        int[] k = getColumns();
        for (int i = 0; i < k.length; i++) {
            if (Value.isNull(row.item(k[i]))) {
                discrim = rowId;
                break;
            }
        }
        return Key.makeKey(table, row, k, discrim, true);
    }

    public String constraintType() { return "unique"; }

    public final void addExportConstraint(ExportedKeyConstraint ec) {
        if (exportConstraints == null) {
            exportConstraints = new Vector();
        }
        exportConstraints.addElement(ec.getName());
    }

    public final Enumeration getExportConstraints() {
        if (exportConstraints == null) {
            return new Vector().elements();
        } else {
            return exportConstraints.elements();
        }
    }

    public final void removeExportConstraint(String name) throws SQLException {
        int pos = -1;
        if (exportConstraints != null) {
            for (int i = 0; i < exportConstraints.size() && pos < 0; i++) {
                if (name.equals(exportConstraints.elementAt(i).toString())) {
                    pos = i;
                }
            }
        }
        if (pos == -1) {
            throw new SQLException("removeExportConstraint(" + name + 
                                   "), not found");
        }
        exportConstraints.removeElementAt(pos);
    }

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

}