Quadcap Embeddable Database

com/quadcap/sql/AutoNumberConstraint.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.TypeBigInt;
import com.quadcap.sql.types.Value;
import com.quadcap.sql.types.ValueLong;

import com.quadcap.util.Debug;

/**
 * Constraint class for SQL <b>AUTO_NUMBER</b> constraints.
 *
 * @author Stan Bailes
 */
public class AutoNumberConstraint
    extends Constraint implements Externalizable
{
    transient AutoNumberStep            step;
    
    long                         current  = -1;

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

    /**
     * Explicit name constructor
     */
    public AutoNumberConstraint(String name) {
        super(name);
    }

    /**
     * When added, I need to number all rows which already exist in the
     * table
     */
    public void add(Session session) throws SQLException {
        if (!table.isUnderConstruction()) {
            try {
                Column col = getColumn();
                col.isAutoIncr = true;
                session.getDatabase().updateRelation(table);
            } catch (IOException e) {
                throw DbException.wrapThrowable(e);
            }
        }
    }

    /**
     * My column is no longer an auto-incrementer
     */
    public void delete(Session session) throws SQLException, IOException {
        Column col = getColumn();
        col.isAutoIncr = false;
        session.getDatabase().updateRelation(table);
    }

    /**
     * Our work is already done.  (We gave out the number in checkInsert())
     */
    public void applyInsert(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    /**
     * We don't care about deletes.
     */
    public void checkDelete(Session session, Row row, long rowId)
        throws SQLException, IOException
    {
    }
    
    /**
     * We don't care about deletes.
     */
    public void applyDelete(Session session, Row row, long rowId,
                            Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    static Object               stepLock = new Object();

    /**
     * If the 'with identity' field is null or not an integer
     * we assign the number before the insert operation and increment
     * our little counter. 
     */
    public void checkInsert(Session session, Row row)
        throws SQLException, IOException
    {
        Column c = getColumn();
        int col = c.getColumn();
        boolean incr = false;
        Value v = row.item(col);
        Database db = session.getDatabase();
        
        if (Value.isNull(v)) {
            incr = true;
        } else {
            Value t = v.convert(TypeBigInt.typeBigInt);
            if (!(t instanceof ValueLong)) {
                incr = true;
            } else {
                ValueLong l = (ValueLong)t;
                current = db.getTableIdentity(table.getName());
                if (l.longValue() >= current) {
                    current = l.longValue() + 1;
                    synchronized (stepLock) {
                        if (step == null) {
                            step = new AutoNumberStep(session, table, current);
                        } else {
                            step.setCurrentId(current);
                        }
                        session.doStep(step);   // go ahead and do it...
                    }
                }
            }
        }

        if (incr) {
            if (true || current < 0) {
                // XXX We can't optimize this away in all cases, because
                // XXX the value of 'current' that's stored locally may
                // XXX be wrong.  This can happen if the table containing
                // XXX this constraint isn't updated properly.
                current = db.getTableIdentity(table.getName());
            }
            session.setLastInsertId(current);
            row.set(col, new ValueLong(current++));
            // we avoid an allocation per step by doing a static allocation,
            // but then we need to protect the shared resource from contention
            synchronized (stepLock) {
                if (step == null) {
                    step = new AutoNumberStep(session, table, current);
                } else {
                    step.setCurrentId(current);
                }
                session.doStep(step);   // go ahead and do it...
            }
        }
    }

    /**
     * We only operate during INSERT, basically.
     */
    public void checkUpdate(Session session, byte[] oldKey, Row row,
                            Row oldRow, long rowId, Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    /**
     * 's cool.
     */
    public void applyUpdate(Session session, byte[] oldKey, Row row,
                            Row oldRow, long rowId, Constraint activeIndex)
        throws SQLException, IOException
    {
    }

    /**
     * Where did I leave off?
     */
    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        super.readExternal(in);
        current = in.readLong();
    }

    /**
     * Remember where we were.
     */
    public void writeExternal(ObjectOutput out) throws IOException {
        super.writeExternal(out);
        out.writeLong(current);
    }

    /**
     * Do me first.
     */
    public int getPriority() { return 0; }
}