HSQLDB example source code file (SubQuery.java)

This example HSQLDB source code file (SubQuery.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - HSQLDB tags/keywords

database, database, hsqlexception, object, object, objectcomparator, result, select, subquery, subquery, table, view, view

The HSQLDB SubQuery.java source code

/* Copyright (c) 2001-2008, 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 HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
 * 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.
 */


package org.hsqldb;

import org.hsqldb.lib.ObjectComparator;

/**
 * Represents an SQL view or anonymous subquery (inline virtual table
 * descriptor) nested within an SQL statement. <p>
 *
 * Implements {@link org.hsqldb.lib.ObjectComparator ObjectComparator} to
 * provide the correct order of materialization for nested views / subqueries.
 *
 * @author boucherb@users
 * @author fredt@users
 */
class SubQuery implements ObjectComparator {

    int     level;
    boolean hasParams;
    boolean isResolved;
    boolean isExistsPredicate;
    boolean uniqueRows;
    Select  select;
    Table   table;
    View    view;
    boolean isMaterialised;

    void populateTable(Session session) throws HsqlException {

        Result r = select.getResult(session, isExistsPredicate ? 1
                                                               : 0);

        if (uniqueRows) {
            r.removeDuplicates(session, select.iResultLen);
        }

        table.insertResult(session, r);
    }

    /**
     * This results in the following sort order:
     *
     * view subqueries, then other subqueries
     *
     *    view subqueries:
     *        views sorted by creation order (earlier declaration first)
     *
     *    other subqueries:
     *        subqueries sorted by depth within select query (deep == higher level)
     *
     */
    public int compare(Object a, Object b) {

        SubQuery sqa = (SubQuery) a;
        SubQuery sqb = (SubQuery) b;

        if (sqa.view == null && sqb.view == null) {
            return sqb.level - sqa.level;
        } else if (sqa.view != null && sqb.view != null) {
            Database db = sqa.view.database;
            int      ia = db.schemaManager.getTableIndex(sqa.view);
            int      ib = db.schemaManager.getTableIndex(sqb.view);

            if (ia == -1) {
                ia = db.schemaManager.getTables(
                    sqa.view.getSchemaName()).size();
            }

            if (ib == -1) {
                ib = db.schemaManager.getTables(
                    sqb.view.getSchemaName()).size();
            }

            int diff = ia - ib;

            return diff == 0 ? sqb.level - sqa.level
                             : diff;
        } else {
            return sqa.view == null ? 1
                                    : -1;
        }
    }
}