/*
* Copyright (c) 1998-2010 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.Database;
import com.caucho.db.table.TableIterator;
import com.caucho.db.xa.Transaction;
import com.caucho.sql.SQLExceptionWrapper;
import java.io.IOException;
import java.sql.SQLException;
import java.util.logging.Logger;
public class ExistsQuery extends SelectQuery {
private static Expr []_nullExprs = new Expr[0];
protected ExistsQuery(Database db, String sql)
throws SQLException
{
super(db, sql);
}
/**
* Executes the query.
*/
public boolean exists(QueryContext context, Transaction xa)
throws SQLException
{
SelectResult result = SelectResult.create(_nullExprs, null);
try {
TableIterator []rows = result.initRows(getFromItems());
context.init(xa, rows, isReadOnly());
return execute(result, rows, context, xa);
} catch (IOException e) {
throw new SQLExceptionWrapper(e);
} finally {
context.unlock();
result.close();
}
}
/**
* Executes the query.
*/
private boolean execute(SelectResult result,
TableIterator []rows,
QueryContext context,
Transaction transaction)
throws SQLException, IOException
{
FromItem []fromItems = getFromItems();
int rowLength = fromItems.length;
return start(rows, rowLength, context, transaction);
}
/**
* Executes the query.
*/
public void execute(QueryContext queryCtx, Transaction xa)
throws SQLException
{
throw new UnsupportedOperationException();
}
}