constraint.java

Java写的含有一个jdbc驱动的小型数据库数据库引擎

/*
 * Constraint.java
 *
 * Copyright (c) 2001, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This package is based on HypersonicSQL, originally developed by Thomas Mueller.
 *
 */
package org.hsqldb;

import java.sql.SQLException;

/**
 * Class declaration
 *
 *
 * @version 1.0.0.1
 */
class Constraint {
    final static int FOREIGN_KEY = 0, MAIN = 1, UNIQUE = 2;
    private int      iType;
    private int      iLen;

    // Main is the table that is referenced
    private Table    tMain;
    private int      iColMain[];
    private Index    iMain;
    private Object   oMain[];

    // Ref is the table that has a reference to the main table
    private Table    tRef;
    private int      iColRef[];
    private Index    iRef;
    private Object   oRef[];

    /**
     * Constructor declaration
     *
     *
     * @param type
     * @param t
     * @param col
     */
    Constraint(int type, Table t, int col[]) {
	iType = type;
	tMain = t;
	iColMain = col;
	iLen = col.length;
    }

    /**
     * Constructor declaration
     *
     *
     * @param type
     * @param main
     * @param ref
     * @param cmain
     * @param cref
     */
    Constraint(int type, Table main, Table ref, int cmain[],
	       int cref[]) throws SQLException {
	iType = type;
	tMain = main;
	tRef = ref;
	iColMain = cmain;
	iColRef = cref;
	iLen = cmain.length;

	if (Trace.ASSERT) {
	    Trace.assert(cmain.length == cref.length);
	}

	oMain = tMain.getNewRow();
	oRef = tRef.getNewRow();
	iMain = tMain.getIndexForColumns(cmain);
	iRef = tRef.getIndexForColumns(cref);
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    int getType() {
	return iType;
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    Table getMain() {
	return tMain;
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    Table getRef() {
	return tRef;
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    int[] getMainColumns() {
	return iColMain;
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    int[] getRefColumns() {
	return iColRef;
    }

    /**
     * Method declaration
     *
     *
     * @param old
     * @param n
     *
     * @throws SQLException
     */
    void replaceTable(Table old, Table n) throws SQLException {
	if (old == tMain) {
	    tMain = n;
	} else if (old == tRef) {
	    tRef = n;
	} else {
	    Trace.assert(false, "could not replace");
	}
    }

    /**
     * Method declaration
     *
     *
     * @param row
     *
     * @throws SQLException
     */
    void checkInsert(Object row[]) throws SQLException {
	if (iType == MAIN || iType == UNIQUE) {

	    // inserts in the main table are never a problem
	    // unique constraints are checked by the unique index
	    return;
	}

	// must be called synchronized because of oMain
	for (int i = 0; i < iLen; i++) {
	    Object o = row[iColRef[i]];

	    if (o == null) {

		// if one column is null then integrity is not checked
		return;
	    }

	    oMain[iColMain[i]] = o;
	}

	// a record must exist in the main table
	Trace.check(iMain.find(oMain) != null,
		    Trace.INTEGRITY_CONSTRAINT_VIOLATION);
    }

    /**
     * Method declaration
     *
     *
     * @param row
     *
     * @throws SQLException
     */
    void checkDelete(Object row[]) throws SQLException {
	if (iType == FOREIGN_KEY || iType == UNIQUE) {

	    // deleting references are never a problem
	    // unique constraints are checked by the unique index
	    return;
	}

	// must be called synchronized because of oRef
	for (int i = 0; i < iLen; i++) {
	    Object o = row[iColMain[i]];

	    if (o == null) {

		// if one column is null then integrity is not checked
		return;
	    }

	    oRef[iColRef[i]] = o;
	}

	// there must be no record in the 'slave' table
	Trace.check(iRef.find(oRef) == null,
		    Trace.INTEGRITY_CONSTRAINT_VIOLATION);
    }

    /**
     * Method declaration
     *
     *
     * @param col
     * @param deleted
     * @param inserted
     *
     * @throws SQLException
     */
    void checkUpdate(int col[], Result deleted,
		     Result inserted) throws SQLException {
	if (iType == UNIQUE) {

	    // unique constraints are checked by the unique index
	    return;
	}

	if (iType == MAIN) {
	    if (!isAffected(col, iColMain, iLen)) {
		return;
	    }

	    // check deleted records
	    Record r = deleted.rRoot;

	    while (r != null) {

		// if a identical record exists we don't have to test
		if (iMain.find(r.data) == null) {
		    checkDelete(r.data);
		}

		r = r.next;
	    }
	} else if (iType == FOREIGN_KEY) {
	    if (!isAffected(col, iColMain, iLen)) {
		return;
	    }

	    // check inserted records
	    Record r = inserted.rRoot;

	    while (r != null) {
		checkInsert(r.data);

		r = r.next;
	    }
	}
    }

    /**
     * Method declaration
     *
     *
     * @param col
     * @param col2
     * @param len
     *
     * @return
     */
    private boolean isAffected(int col[], int col2[], int len) {
	if (iType == UNIQUE) {

	    // unique constraints are checked by the unique index
	    return false;
	}

	for (int i = 0; i < col.length; i++) {
	    int c = col[i];

	    for (int j = 0; j < len; j++) {
		if (c == col2[j]) {
		    return true;
		}
	    }
	}

	return false;
    }

}