Quadcap Embeddable Database

com/quadcap/sql/ForeignKeyConstraint.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
 * 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.Vector;

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

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

import com.quadcap.sql.index.Btree;
import com.quadcap.sql.index.Comparator;

/**
 * Abstract base class for imported and exported key constraints.
 *
 * @author Stan Bailes
 */
public abstract class ForeignKeyConstraint
    extends Constraint
    implements Externalizable
{    
    String                              fTableName;
    Vector                              fColNames;
    Table                               fTable;
    UniqueConstraint                    fConstraint;
    int[]                               fCols;
    transient Comparator                compare;

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

    public ForeignKeyConstraint(String name, String fTableName) {
        super(name);
        this.fTableName = fTableName;
    }

    public ForeignKeyConstraint(String name, Vector colNames,
                                String fTableName, Vector fColNames) {
        super(name, colNames);
        this.fTableName = fTableName;
        this.fColNames = fColNames;
    }
    
    /**
     * Reset any mapped columns (e.g. in case a column is added or deleted)
     */
    public void resetColumns() throws SQLException {
        super.resetColumns();
        fCols = null;
    }

    public void checkInsert(Session session, Row row)
        throws SQLException, IOException
    {
    }
    
    public void applyInsert(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }
    
    public void checkUpdate(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 checkDelete(Session session, Row row, long rowId)
        throws SQLException, IOException
    {
    }
    
    public void applyDelete(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }
    
    /**
     * Is this constraint 'deferred'?
     */
    public final boolean isDeferred() {
        return (spec & INIT_DEFERRED) != 0;
    }

    final Comparator getComparator() throws SQLException {
        if (compare == null) compare = new Key(getColumns().length);
        return compare;
    }

    /**
     * Create a candidate key for a row from this table
     */
    public byte[] makeKey(Session session, Row row)
        throws SQLException
    {
        return makeKey(row, getColumns());
    }

    /**
     * Create a candidate key for a row from the foreign table
     */
    public byte[] makeFKey(Session session, Row row)
        throws IOException, SQLException
    {
        return makeKey(row, getFCols(session.getDatabase()));
    }

    private final byte[] makeKey(Row row, int[] k) throws SQLException {
        return Key.makeKey(null, row, k, 0, false);
    }

    public void setForeignColumn(String name) {
        fColNames = new Vector();
        fColNames.addElement(name);
    }

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

    public String getFTableName() {
        return fTableName;
    }

    public void setFTableName(String s) {
        fTableName = s;
    }

    public Table getFTable(Database db) throws SQLException, IOException {
        if (fTable == null) {
            Relation t = db.getRelation(fTableName);
            if (t == null) {
                throw new SQLException("No such table: " + fTableName,
                                       "42000");
            }
            try {
                fTable = (Table)t;
            } catch (ClassCastException e) {
                throw new SQLException("Not a base table: " + fTableName,
                                       "42000");
            }
        }
        return fTable;
    }

    /**
     * If you care, remember to 'extend' and embrace.
     */
    public void add(Session session) throws SQLException, IOException {}
    
    abstract public void delete(Session session)
        throws SQLException, IOException
    ;

    /**
     * 
     */
    public int[] getFCols(Database db) throws SQLException, IOException {
        if (fCols == null) {
            if (fColNames == null) {
                UniqueConstraint pk = getFTable(db).getPrimaryKey();
                if (pk == null) {
                    throw new SQLException("No primary key for table " +
                                           fTable.getName());
                }
                fConstraint = pk;
                fCols = pk.getColumns();
            } else {
                fCols = getFTable(db).mapColumns(fColNames);
                fConstraint = fTable.getIndexForColumns(fCols);
            }
        }
        return fCols;
    }

    boolean isSelfReferencing(Database db) throws IOException, SQLException {
        boolean ret = table == getFTable(db);
        return ret;
    }

    public String toString() {
        StringBuffer sb = new StringBuffer(super.toString());
        sb.append(" references " + fTableName + "(");
        if (fColNames != null) {
            for (int i = 0; i < fColNames.size(); i++) {
                if (i > 0) sb.append(",");
                sb.append(fColNames.elementAt(i).toString());
            }
        }
        sb.append(')');
        return sb.toString();
    }
}