rowiterateexpr.java

来自「RESIN 3.2 最新源码」· Java 代码 · 共 102 行

/*
 * Copyright (c) 1998-2008 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Resin Open Source is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *   Free SoftwareFoundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.db.sql;

import com.caucho.db.table.TableIterator;
import com.caucho.log.Log;

import java.io.IOException;
import java.sql.SQLException;
import java.util.logging.Logger;

class RowIterateExpr extends Expr {
  private static final Logger log = Log.open(RowIterateExpr.class);
  
  /**
   * Sets the initial row.
   */
  boolean init(QueryContext context, TableIterator rowIter)
    throws SQLException, IOException
  {
    rowIter.init(context);

    return nextBlock(context, rowIter);
  }

  /**
   * Initializes the current row.
   */
  boolean initRow(QueryContext context, TableIterator rowIter)
    throws SQLException, IOException
  {
    rowIter.initRow();

    return rowIter.nextRow();
  }

  /**
   * Returns the next row.
   */
  boolean nextRow(QueryContext context, TableIterator rowIter)
    throws IOException, SQLException
  {
    return rowIter.nextRow();
  }

  /**
   * Returns true if shifing the child rows will make a difference.
   */
  boolean allowChildRowShift(QueryContext context, TableIterator rowIter)
  {
    return true;
  }

  /**
   * Returns the next block.
   */
  boolean nextBlock(QueryContext context, TableIterator rowIter)
    throws IOException, SQLException
  {
    context.unlock();
    
    while (rowIter.nextBlock()) {
      context.lock();

      rowIter.initRow();

      if (rowIter.nextRow())
	return true;
      
      context.unlock();
    }
    
    return false;
  }
}