Quadcap Embeddable Database

com/quadcap/sql/AddConstraint.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.io.Extern;

import com.quadcap.util.Debug;

/**
 * Log step to add a constraint to a table.
 *
 * @author Stan Bailes
 */
public class AddConstraint extends LogStep implements Externalizable {
    transient Table                     table;

    Constraint                          constraint;
    String                              tableName               = null;
    boolean                             global;

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

    /**
     * Explicit constructor: {table, constraint, global flag}
     */
    public AddConstraint(Session session, Table table, Constraint constraint,
                         boolean global) {
        super(session);
        this.table = table;
        this.constraint = constraint;
        table.nameConstraint(constraint);
        this.global = global;
        this.tableName = table.getName();
    }

    /**
     * Constructor for a non-global constraint
     */
    public AddConstraint(Session session, Table table, Constraint constraint) {
        this(session, table, constraint, false);
    }

    /**
     * Lazy table accessor
     */
    Table getTable(Database db) throws IOException {
        if (table == null) {
            table = (Table)db.getRelation(tableName);
        }
        return table;
    }

    /**
     * LogStep.undo(): delete the constraint; perform any constraint-specified
     * cleanup, and remove the constraint from the table.
     */
    public void undo(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        getTable(db);
        constraint = table.getConstraint(constraint.getName());
        // Generally, we will have a constraint here.  But if things have
        // already gone badly, the constraint might not have actually been
        // added.  So don't freak out if you can't find it.
        if (constraint != null) {
            table.deleteConstraint(constraint.getName());
            constraint.undoAdd(session);
            db.updateRelation(table);
            db.deleteIndex(constraint.getName());
        }
    }

    /**
     * LogStep.redo(): add the constrtaint, perform any constraint-specific
     * initialization, and update the table with the new constraint
     */
    public void redo(Session session) throws IOException, SQLException {
        Database db = session.getDatabase();
        getTable(db);
        table.addConstraint(constraint);
        constraint.add(session);
        db.updateRelation(table);
        db.addIndex(constraint.getName(), tableName);
    }

    /**
     * LogStep.prepare(): A good constraint prepares his table, anyway
     */
    public void prepare(Session session) throws IOException, SQLException {
        constraint.setTable(getTable(session.getDatabase()));
    }

    /**
     * Read me from a stream
     */
    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        super.readExternal(in);
        this.constraint = (Constraint)in.readObject();
        this.tableName = (String)in.readObject();
        this.global = in.read() == 1;
    }

    /**
     * Write me to a stream
     */
    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);
        out.writeObject(constraint);
        out.writeObject(tableName);
        out.write(global ? 1 : 0);
    }

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

    //#ifdef DEBUG
    public String toString() {
        StringBuffer sb = new StringBuffer(super.toString());
        sb.append(" AddConstraint(");
        sb.append(tableName);
        sb.append(',');
        sb.append(constraint == null ? "null" : constraint.toString());
        return sb.toString();
    }
    //#endif

}