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HSQLDB example source code file (View.java)

This example HSQLDB source code file (View.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

expression, hsqlexception, hsqlexception, hsqlname, hsqlname, intkeyhashmap, iterator, select, select, string, string, subquery, tokenizer, view

The HSQLDB View.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.HsqlNameManager.HsqlName;
import org.hsqldb.lib.HsqlArrayList;
import org.hsqldb.lib.Iterator;
import org.hsqldb.lib.IntKeyHashMap;
import org.hsqldb.lib.ArrayUtil;

// fredt@users 20020420 - patch523880 by leptipre@users - VIEW support - modified
// fredt@users 20031227 - remimplementated as compiled query

/**
 * Represents an SQL VIEW based on a SELECT statement.
 *
 * @author leptipre@users
 * @author fredt@users
 * @version 1.8.0
 * @since 1.7.0
 */
class View extends Table {

    Select             viewSelect;
    SubQuery           viewSubQuery;
    private String     statement;
    private HsqlName[] colList;

    /** schema at the time of compilation */
    HsqlName compileTimeSchema;

    /**
     * List of subqueries in this view in order of materialization. Last
     * element is the view itself.
     */
    SubQuery[] viewSubqueries;

    /**
     * Constructor.
     * @param Session
     * @param db database
     * @param name HsqlName of the view
     * @param definition SELECT statement of the view
     * @param columns array of HsqlName column names
     * @throws HsqlException
     */
    View(Session session, Database db, HsqlName name, String definition,
            HsqlName[] columns) throws HsqlException {

        super(db, name, VIEW);

        isReadOnly        = true;
        colList           = columns;
        statement         = trimStatement(definition);
        compileTimeSchema = session.getSchemaHsqlName(null);

        compile(session);
        replaceAsterisksInStatement();

        HsqlName[] schemas = getSchemas();

        for (int i = 0; i < schemas.length; i++) {
            if (db.schemaManager.isSystemSchema(schemas[i])) {
                continue;
            }

            if (!schemas[i].equals(name.schema)) {
                throw Trace.error(Trace.INVALID_SCHEMA_NAME_NO_SUBCLASS);
            }
        }
    }

    /**
     * Returns the SELECT statement trimmed of any terminating SQL
     * whitespace, separators or SQL comments.
     */
    static String trimStatement(String s) throws HsqlException {

        int       position;
        String    str;
        Tokenizer tokenizer = new Tokenizer(s);

        // fredt@users - this establishes the end of the actual statement
        // to get rid of any end semicolon or comment line after the end
        // of statement
        do {
            position = tokenizer.getPosition();
            str      = tokenizer.getString();
        } while (str.length() != 0 || tokenizer.wasValue());

        return s.substring(0, position).trim();
    }

    /**
     * Compiles the SELECT statement and sets up the columns.
     */
    void compile(Session session) throws HsqlException {

        // create the working table
        Parser p = new Parser(session, this.database,
                              new Tokenizer(statement));

        p.setCompilingView();

        int brackets = p.parseOpenBracketsSelect();

        viewSubQuery = p.parseSubquery(brackets, colList, true,
                                       Expression.VIEW);

        p.setAsView(this);

        viewSubqueries = p.getSortedSubqueries();
        viewSelect     = viewSubQuery.select;

        viewSelect.prepareResult(session);

        Result.ResultMetaData metadata = viewSelect.resultMetaData;
        int                   columns  = viewSelect.iResultLen;

        if (super.columnCount == 0) {

            // do not add columns at recompile time
            super.addColumns(metadata, columns);
        }
    }

    /**
     * Returns the SELECT statement for the view.
     */
    String getStatement() {
        return statement;
    }

    /**
     *  is a private helper for replaceAsterisksInStatement, to avoid some code duplication
     */
    private void collectAsteriskPos(final Select select,
                                    IntKeyHashMap asteriskPositions) {

        if (select.asteriskPositions == null) {
            return;
        }

        Iterator asterisks = select.asteriskPositions.keySet().iterator();

        while (asterisks.hasNext()) {
            int pos = asterisks.nextInt();

            asteriskPositions.put(pos, select.asteriskPositions.get(pos));
        }

        // The following is to guarantee the invariant of this class, that the |astersiskPositions|
        // member of the various Select instances properly describe the occurances
        // of Expression.ASTERISK in the statement.
        // Since we are going to replace all those asterisks, we also need to reset the various
        // |astersiskPositions| instances, which is best done here were all non-null
        // Select's need to pass by.
        select.asteriskPositions = null;
    }

    /**
     *  replaces all asterisks in our statement with the actual column list
     *
     *  This way, we ensure what is required by the standard: a view returns a result
     *  which reflects the structure of the underlying tables at the *time of the definition
     *  of the view.
     */
    private void replaceAsterisksInStatement() throws HsqlException {

        IntKeyHashMap asteriskPositions = new IntKeyHashMap();

        // asterisk positions in sub queries
        for (int i = 0; i < viewSubqueries.length; ++i) {

            // collect the occurances of asterisks in the statement
            Select subSelect = viewSubqueries[i].select;

            collectAsteriskPos(subSelect, asteriskPositions);

            // the same for all (possible) UNION SELECTs of the sub select
            if (subSelect.unionArray != null) {

                // start with index 1, not 0 - the first select is the one already covered by subSelect
                for (int u = 1; u < subSelect.unionArray.length; ++u) {
                    collectAsteriskPos(subSelect.unionArray[u],
                                       asteriskPositions);
                }
            }
        }

        int[]    positions = new int[asteriskPositions.size()];
        Iterator it        = asteriskPositions.keySet().iterator();

        for (int i = 0; i < positions.length; i++) {
            positions[i] = it.nextInt();
        }

        ArrayUtil.sortArray(positions);

        StringBuffer expandedStatement = new StringBuffer();
        int          lastPos           = 0;
        String       segment;

        for (int i = 0; i < positions.length; i++) {
            int    pos     = positions[i];
            String colList = (String) asteriskPositions.get(pos);

            if (colList == null) {
                continue;
            }

            segment = statement.substring(lastPos, pos);
            lastPos = statement.indexOf("*", pos) + 1;

            expandedStatement.append(segment);
            expandedStatement.append(' ');
            expandedStatement.append(colList);
            expandedStatement.append(' ');
        }

        segment = statement.substring(lastPos, statement.length());

        expandedStatement.append(segment);

        statement = expandedStatement.toString();
    }

    /**
     * Overridden to disable SET TABLE READONLY DDL for View objects.
     */
    void setDataReadOnly(boolean value) throws HsqlException {
        throw Trace.error(Trace.NOT_A_TABLE);
    }

    /**
     * Returns list of schemas
     */
    HsqlName[] getSchemas() {

        HsqlArrayList list = new HsqlArrayList();

        for (int i = 0; i < viewSubqueries.length; i++) {
            Select select = viewSubqueries[i].select;

            for (; select != null; select = select.unionSelect) {
                TableFilter[] tfilter = select.tFilter;

                for (int j = 0; j < tfilter.length; j++) {
                    list.add(tfilter[j].filterTable.tableName.schema);
                }
            }
        }

        return (HsqlName[]) list.toArray(new HsqlName[list.size()]);
    }

    boolean hasView(View view) {

        if (view == this) {
            return false;
        }

        for (int i = 0; i < viewSubqueries.length; i++) {
            if (viewSubqueries[i].view == view) {
                return true;
            }
        }

        return false;
    }

    /**
     * Returns true if the view references any column of the named table.
     */
    boolean hasTable(Table table) {

        for (int i = 0; i < viewSubqueries.length; i++) {
            Select select = viewSubqueries[i].select;

            for (; select != null; select = select.unionSelect) {
                TableFilter[] tfilter = select.tFilter;

                for (int j = 0; j < tfilter.length; j++) {
                    if (table.equals(tfilter[j].filterTable.tableName)) {
                        return true;
                    }
                }
            }
        }

        return false;
    }

    /**
     * Returns true if the view references the named column of the named table,
     * otherwise false.
     */
    boolean hasColumn(Table table, String colname) {

        if (hasTable(table)) {
            Expression.Collector coll = new Expression.Collector();

            coll.addAll(viewSubqueries[viewSubqueries.length - 1].select,
                        Expression.COLUMN);

            Iterator it = coll.iterator();

            for (; it.hasNext(); ) {
                Expression e = (Expression) it.next();

                if (colname.equals(e.getBaseColumnName())
                        && table.equals(e.getTableHsqlName())) {
                    return true;
                }
            }
        }

        return false;
    }

    /**
     * Returns true if the view references the named SEQUENCE,
     * otherwise false.
     */
    boolean hasSequence(NumberSequence sequence) {

        Expression.Collector coll = new Expression.Collector();

        coll.addAll(viewSubqueries[viewSubqueries.length - 1].select,
                    Expression.SEQUENCE);

        Iterator it = coll.iterator();

        for (; it.hasNext(); ) {
            Expression e = (Expression) it.next();

            if (e.valueData == sequence) {
                return true;
            }
        }

        return false;
    }
}

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